research paper on plant community

ORIGINAL RESEARCH article

Plant community assembly is jointly shaped by environmental and dispersal filtering along elevation gradients in a semiarid area, china.

• 1 Key Laboratory of Eco-Environments in the Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in the Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, China
• 2 Biological Science Research Center, Academy for Advanced Interdisciplinary Studies, Southwest University, Chongqing, China
• 3 State Key Laboratory of Seedling Bioengineering, Ningxia Forestry Institute, Yinchuan, China

Environmental filtering (EF) and dispersal filtering (DF) are widely known to shape plant community assembly. Particularly in arid and semi-arid mountainous regions, however, it remains unclear whether EF or DF dominate in the community assembly of different life forms or how they interact along elevational gradients. This research aims to reveal how different ecological processes influence herbaceous and woody community assembly and how they respond to various environmental drivers and elevational gradients. Here we integrated taxonomic diversity (TD), phylogenetic diversity (PD), and ecological drivers across an elevational gradient of 1,420 m in the Helan Mountain Nature Reserve, in typical arid and semi-arid areas of China. This study showed that the TD and PD of herbaceous communities significantly increase linearly with changing elevation gradients, while woody ‘TD’ showed a unimodal pattern, and there was little relationship between woody ‘PD’ and elevation. Herbaceous species exhibited significant phylogenetic clustering at low elevations, where they were influenced by climate, aspect, and tree cover. However, woody species exhibited random patterns across elevations. Herbaceous and woody species’ taxonomic and phylogenetic beta diversity is governed primarily by spatial turnover rather than nestedness. Spatial turnover is caused primarily by EF and DF’s combined influence, but their relative importance differs between herbaceous and woody communities. Therefore, we conclude that the responses of herbaceous and woody plants along elevation gradients in the Helan Mountains are decoupled due to their different adaptation strategies to climate factors in the drylands. These findings are important for understanding the assembly mechanisms driving plant communities in dryland under the context of dramatic increases in drought driven by climate warming.

Introduction

Mountains are hotspots of biodiversity, covering 24% of the total geographical area and supporting about 50% of the planet’s biodiversity ( Körner et al., 2011 ) They provide refuge for many plants and animals due to the various conditions created by the complex topography and could play an important role in protecting biodiversity ( Becker et al., 2007 ; Körner et al., 2011 ; Yuancai et al., 2022 ). Mountains often establish unique local climates along elevation gradients ( Wang et al., 2022 ). Continuous change in landscape and climate factors across elevation leads to variations in resource availability (i.e., light and moisture), creating different microenvironmental conditions within short distances ( Becker et al., 2007 ; Ahmad et al., 2020 ; Behzad et al., 2022 ). It leads to a sharp transformation in the ecophysiological adaptation of plants ( Jiang et al., 2016 ) and ultimately alters their diversity patterns along elevation gradients ( Boscutti et al., 2018 ). Because of their steep climatic gradients, mountains are considered sentinels of global warming and, therefore, offer a unique field laboratory for understanding the mechanisms driving the evolution and maintenance of biodiversity along elevation gradients ( Körner et al., 2016 ).

Elevation-diversity relationships have been popular in ecology, biogeography, and biodiversity conservation in recent decades ( Körner et al., 2011 ; Shahriari et al., 2019 ; Montano-Centellas et al., 2021 ). Previous studies about biodiversity patterns along elevation gradients found an evident disparity in elevation-richness relationships worldwide ( Berhanu et al., 2016 ; Zhang et al., 2016 ; Mayor et al., 2017 ). The maximum species diversity occurs in the mid-elevation range ( Grytnes, 2003 ), but decreases or increases in species richness along elevation have also been documented ( Zhu et al., 2009 ; Berhanu et al., 2016 ; Qianwen et al., 2022 ). Yet, contemporary changes in biodiversity across the globe have been investigated based largely on taxonomic diversity (TD; i.e., species identity) ( Li et al., 2020 ), which does not necessarily reflect changes in phylogenetic diversity (PD) ( Faith, 1992 ). To solve this problem, Webb et al. (2002) developed the basis for using phylogenetic data to discover the influence of deterministic processes on community assembly. The method based on PD, considering the phytogeographical affinities that drive community assemblages ( Webb et al., 2002 ), has been used to reveal species diversity in elevation gradients ( Dainese et al., 2015 ; Wang et al., 2022 ). Combining TD and PD has been increasingly recommended to reveal the underlying driving mechanisms of community assemblages ( Li et al., 2020 ; Macheroum et al., 2021 ) because it provides more comprehensive information on community assembly from ecological and evolutionary processes at the α and β diversity scales ( Li et al., 2020 ; Du et al., 2021 ). Approaches that relate local processes to regional and evolutionary processes based on PD or spatial turnover will quantify the elevation-diversity relationship from an ecological and evolutionary perspective ( Webb et al., 2002 ). However, to date, the assembly mechanisms driving plant communities along elevational gradients remain well elusive ( Luo et al., 2019 ).

Theories of community assemblages, including niche-based processes and stochastic processes ( Montano-Centellas et al., 2021 ), considered processes of species dispersal, species persistence, and species coexistence, were used to illustrate the species assembly ( Webb et al., 2002 ; Grigoropoulou et al., 2022 ). Niche theory highlights the role of environmental filtering (EF; species with specific traits coexist under specific environmental stresses) and biological interactions (competitive exclusion causes limiting similarity) ( Wang et al., 2021 ). Webb et al. (2002) claimed that interspecific competition might result in a community pattern of phylogenetic overdispersion. It might also result in phylogenetic clustering if certain clades have stronger competitiveness than others. Some evidence suggests that high-elevation habitats are generally under harsher conditions (low temperatures, dramatic temperature fluctuations) ( Wang et al., 2021 ), in which plant community compositions are more sensitive to climate change than those of low-elevation habitats ( Sproull et al., 2015 ). In contrast, the neutral theory holds that stochastic fluctuations and dispersal filtering (DF) independently determine the patterns of community assembly ( Tilman, 2004 ; Hubbell, 2005 ). It is now commonly accepted that community assembly is determined by both processes ( Farjalla et al., 2012 ; Grigoropoulou et al., 2022 ). Recent studies demonstrate that EF could become more critical for shaping plant community structure in stressful environmental conditions, while DF might dominate under benign conditions ( Pouteau et al., 2019 ). Thus, a shift in the community assembly from overdispersal in low elevations to clustering in high elevations appears to occur. For heterogeneous mountains, however, the species assemblage along elevation gradients may be very complex and show various trends ( Jarzyna et al., 2021 ; Montano-Centellas et al., 2021 ) for different life-form plants because they have diverged from adaptation strategies to specific environmental factors ( Lee and Chun, 2015 ; Loidi et al., 2021 ; Macheroum et al., 2021 ). Moreover, due to different spatial scales and life forms in terms of evolutionary relationships and dispersal ability ( Liu et al., 2015 ; Shahriari et al., 2019 ), quantifying the relative importance of the EF and DF along elevation gradients remains challenging ( Du et al., 2021 ). Despite knowing that communities are being formed, it remains unclear whether EF or DF dominate in the community assembly of different life forms or how they interact along elevational gradients, especially in arid areas ( Macheroum et al., 2021 ).

Drylands are defined as places with an aridity index of less than 0.65. They encompass over 45% of the planet’s land surface and inhabit over 38% of the Earth’s population ( Peng et al., 2020 ). The drylands of China account for about 10.8% of the world’s drylands, and China is the most drought-affected country in Asia ( Huang et al., 2015 ). The dramatic increase in climate warming-driven drought is considered a potential threat to worldwide biodiversity ( Dai, 2010 ; Jiao et al., 2021 ). Climate change may aggravate dryland degradation through the alteration of spatial and temporal patterns in temperature, rainfall, solar radiation, and winds, leading to vegetation degradation and ecosystem service loss in the drylands ( Macheroum et al., 2021 ; Gul et al., 2022 ). Nevertheless, plant diversity patterns and assembly mechanisms in dryland mountain ranges are not well documented. The Helan Mountains, a typical arid and semi-arid region of China with particularly fragile habitats exposed to extreme climate change, are one example ( Pang et al., 2013 ; Cheng et al., 2020 ). The Helan Mountains are also the boundary line between the grassland and desert areas of Northwest China ( Jiang et al., 2007 ). The vegetation types can be classified as desert grassland, sparse mountain grassland, montane coniferous forest, subalpine scrub meadow or alpine meadow. The vegetation distribution patterns in these regions are strongly influenced by climatic and topographical factors ( Cheng et al., 2020 ; Arif et al., 2022a ; Chen et al., 2022 ). However, to our knowledge, elevation-diversity relationships have not been well revealed in the drylands of China, especially when considering the different life forms of plants.

This study investigated herbaceous and woody communities along elevational gradients in the Helan Mountains of arid and semi-arid regions in Northwest China. Here we integrate taxonomic and phylogenetic diversity and environmental drivers (climatic and topographic variables; Cheng et al., 2020 ) to elucidate how various ecological mechanisms shape herbaceous and woody community assemblages and to reveal how these communities respond to different environmental drivers along elevational gradients. Specifically, we aimed to answer the following key scientific questions:

(1) How do the TD and PD of herbaceous and woody communities vary with changing elevation gradients in the Helan Mountains?

(2) Which factors in the environment impact the TD and PD of herbaceous and woody communities in this area?

(3) How and to what extent do EF and DF affect the spatial turnover of herbaceous and woody species in this region?

Materials and methods

Study area and vegetation surveying.

This research was performed in the Helan Mountains (38°13′ N, 105°41′ E; Figure 1 ), which are situated in arid to semi-arid regions in Northwest China. The climate in this region is primarily subject to the influence of the summer and winter monsoons, with mean annual temperatures ranging from 8.2°C to 8.6°C (-8.54°C in January and 21.43°C in August) and mean annual precipitation of 209.2 ± 57.2 mm, of which around 44% of precipitation occurs during the July-August growing season ( Pang et al., 2013 ). High-elevation areas had lower temperatures and higher precipitation than low-elevation areas ( Jiang et al., 2007 ). Gray cinnamonic soils prevail in this area ( Wang and Yang, 2021 ). It is robust evidence of local vegetation evolution in northern China and its relationship with East Asian summer winds ( Cheng et al., 2020 ). Trees (such as Picea crassifolia , Pinus tabuliformis , and Ajania fruticulose ), shrubs, and grasses are the main land cover types across this region. However, due to the long lifespan and limited distribution of trees, it is difficult to detect tree distribution patterns with changing elevation gradients. Specifically, an interspersed distribution of continuous woody (shrubs and small trees) and grassland dominates in this area. Considering accessibility, we identified 23 study sites with the peak growing season of 2021, from 1,169 m to 2,589 m in the Helan Mountains. At each site, we established a permanent plot (20 m × 20 m) ( Lopez-Angulo et al., 2018 ), and its vegetation structure and composition were assessed by systematic sampling by using the quadrat method, as it has less bias and covers the entire plant composition ( Ahmad et al., 2020 ). Within each permanent plot, five quadrats of 25 m 2 (5 m × 5 m for woody) and 1 m 2 (1 m × 1 m for herbaceous) were sampled ( Shi et al., 2020 ). Each 1 m 2 quadrat was nested within each 25 m 2 quadrat. A total of 230 quadrats were sampled. We recorded and measured all the species’ compositions and abundance in each quadrangle. We found 120 species that came from 90 genera and 41 families.

Figure 1 Map of the study site and plots on Helan Mountain of arid and semi-arid regions in Northwest China.

Taxonomic and phylogenetic diversity metrics

We classified the plants into 44 woody (including all shrubs and trees) and 76 herbaceous species according to the Flora of China ( http://www.iplant.cn/ ) and field observations to understand how different species responded to elevational gradients. To compare the TD and PD of herbaceous and woody communities, species-level phylogenetic trees based on the mega-tree approach were constructed using the “V.PhyloMaker” package ( Smith and Brown, 2018 ; Jin and Qian, 2019 ). The package is the largest dated phylogeny for vascular plants and includes 74,533 species of extant vascular plants ( Jin and Qian, 2019 ). We then used the pruned versions of the tree for calculating the phylogenetic structure of both herbaceous and woody species in each of the 23 communities. We then calculated TD using species richness and PD using the mean pairwise distance (MPD) and the mean nearest taxon distance (MNTD) ( Qian et al., 2019 ). To disentangle the assembly mechanisms of herbaceous and woody communities ( Luo et al., 2019 ), we converted their MPD and MNTD metrics into standardized effect values (SESmpd and SESmntd indices) in the ‘Picante’ package ( Kembel et al., 2010 ). Positive and negative values of SESmpd and SESmntd respectively indicate overdispersal and clustering ( Yakimov et al., 2020 ). Their absolute values are higher than 1.96, meaning that the community structure is significantly overdispersed or clustered compared to null expectations ( Webb et al., 2002 ; Yakimov et al., 2020 ). In addition, to distinguish TD and PD of herbaceous and woody communities at the beta scale, in the “betapart” package, we calculated three pairwise dissimilarity indices ( Baselga, 2010 ; Baselga and Orme, 2012 ), in which the Sørensen dissimilarity (βsor) index measures the overall beta diversity, the Simpson dissimilarity (βsim) index measures the turnover component, and the nestedness dissimilarity (βnes) index measures the nestedness component derived from nestedness-related richness differences.

Environmental and climatic variables

Temperature, precipitation, and their extremes will remarkably influence species’ ecological and evolutionary processes ( Qian et al., 2019 ). Consequently, seven indicators of temperature and precipitation ( Table S1 ) from the WorldClim database ( Hijmans et al., 2005 ) were used to represent the climatic characteristics of the study area. Before the analyses, a principal component analysis (PCA; Table S1 ) was used to prevent the effects of collinearity ( Figure S1 ) ( Dormann et al., 2013 ), and the PCA axes with an interpretation rate higher than 10% were retained for subsequent analysis ( Slik et al., 2013 ), resulting in two axes of climate variables (PC1 and PC2; Figure S2 ). Besides, the slope and aspect (a proxy for topographic heterogeneity; Shiferaw et al., 2018 ) of each plot were determined and closely related to the amount of incoming solar radiations and the construction of different microclimatic conditions ( Pang et al., 2013 ), which is a significant factor that promotes diversification in plant community composition. In addition, the altitude, longitude, and latitude of each plot were recorded with GPS.

Statistical methods

We analyzed the relationship between TD, SESmpd, SESmntd and elevation using simple linear and quadratic regression models (without significant spatial autocorrelation based on Morans’I index, Table S2 ). The analysis considered both linear and quadratic terms but only retained the results for the linear term when the quadratic term was not significant. A linear multiple regression model involving the ordinary least squares (OLS) method was used to identify the role of climate (climate PC1, climate PC2), topographic (slope and aspect), and biotic (woody cover for herbaceous) drivers ( Figure S3 ) in determining a regional disparity in the TD and PD of herbaceous and woody species. Prior to the OLS analyses, all predictors were centered and scaled ( Chun and Lee, 2017 ). To understand the relative contribution of predictor variables to the diversity of herbaceous and woody species, model averaging methods based on Akaike information criterion weights were used in the “MuMIn” package ( Barton, 2019 ). We estimated the coefficients by averaging over all possible models and weighting them according to the probability associated with each model.

We investigated the correlation between taxonomic and phylogenetic turnover based on the βsim index with spatial and environmental distance to evaluate the species turnover along altitudinal gradients by employing the “ecodist” package ( Goslee and Urban, 2007 ). A variance partitioning approach was performed to quantify the relative contribution of EF and DF in taxonomic and phylogenetic turnover. Prior to variation partitioning, the redundancy analysis and the forward selection were executed to reduce redundant components ( Zheng et al., 2021 ). In this analysis, the ‘vegan’ package partitions the total explained variance (R 2 ) into three parts ( Oksanen et al., 2020 ; Shi et al., 2021 ), including their unexplained, joint, and independent effects. The Euclidean distances of five environmental variables (PC1, PC2, elevation, aspect, slope) between 23 sites were chosen to reflect EF, and spatial distances between study sites were selected to reflect DF ( Li et al., 2021 ; Shi et al., 2021 ). We use the adjusted R 2 to estimate the explanatory power of each component because of the different number of explanatory variables in our models.

In addition, to further examine clustering or overdispersion of plant communities, we performed a co-occurrence analysis by calculating the C-score (Checkerboard score; Stone and Roberts, 1990 ), which is a widely used index to measure associations between species pairs. We used null model analyses to quantify whether species co-occurrence patterns deviated from the expectations of a random (stochastic) assembly process ( Ulrich et al., 2012 ). The values obtained were standardized to allow comparisons among assemblages using the standardized effect size (SES). The observed C-score was higher than randomized expectations, indicating that pairs of species co-occurred to a lesser extent than expected at random. The magnitude of SES was interpreted as the strength of the effect of deterministic processes on the assemblage. The C-score was evaluated based on 10,000 simulations and using the sequential swap randomization algorithm with the package “EcoSimR” ( Gotelli et al., 2015 ).

The TD and PD of herbaceous and woody community

The TD (species richness) and PD (SESmpd and SESmntd) of herbaceous communities significantly increased linearly along the elevational gradient ( Figure 2A , Figures 3A, C ) . The nonlinear model was remarkable for woody communities with relatively low richness at the ends of the elevation range and peak richness in the 1500 ~ 1600 m range ( Figure 2B ). However, the PD (SESmpd and SESmntd) of woody communities did not significantly change as elevation increased ( Figures 3B, D ). The SESmpd and SESmntd of herbaceous communities showed random patterns at high elevations (above 2000 m) and were characterized by significant phylogenetic clustering (negative values below ‐1.96) at low elevational sites ( Figures 3A, C ). Surprisingly, all woody communities showed random patterns for SESmpd and SESmntd, except for two communities at low elevations that showed significant phylogenetic clustering for SESmntd ( Figures 3B, D ). Overall, most phylogenetic SESmpd and SESmntd values of herbaceous and woody communities were less than zero, indicating that phylogenetic clustering was driven by deterministic processes. This result was further supported by the co-occurrence analysis, where the observed C-score was higher than the simulated C-score values ( Figure S4 ), indicating a non-random co-occurrence pattern. In addition, the C-score showed a higher standardized effect size (SES) for woody plants compared to herbaceous plants, indicating the greater importance of deterministic processes for woody plant assemblages ( Figure S4 ).

Figure 2 Elevational patterns of species richness of herbaceous (A) and woody (B) . Trend lines and shaded areas represent the fitted values from linear regression with a linear term (A) and quadratic (B) and their 95% confidence intervals, respectively.

Figure 3 Elevational patterns of standardized values of mean phylogenetic structure (SESmpd and SESmntd) of plant communities of herbaceous (A, C) and woody (B, D) . The size of the circle indicates the relative species richness associated with each plot.

For herbaceous communities, climate PC1 and woody cover had significantly negative effects on species richness ( Figure 4A ), whereas SESmntd indices showed significant negative relationships with climate PC1 and aspect, and no relationship between SESmpd and multi-dimensional variables ( Figures 4C, E ). Surprisingly, regional (climatic PC1 and PC2) and local (aspect and slope) variables were not significantly correlated with the TD and PD of woody communities ( Figures 4B, D, F ).

Figure 4 The effects of multi-dimensional variables on the species richness and phylogenetic structure (SESmpd, SESmntd) of plant communities of herbaceous (A, C, E) and woody (B, D, F) . The parameter estimates (standardized model-averaged coefficients for variables) and the associated 95% confidence intervals are shown. Coefficient > 0 represents a positive effect, while coefficient < 0 indicates a negative effect (red). All predictors were centered and scaled to make the coefficients directly comparable.

Taxonomic and phylogenetic beta diversity of herbaceous and woody communities

Overall variation in the taxonomic and phylogenetic β-diversity of the herbaceous and the woody resulted mainly from turnover rather than nestedness ( Figure 5 ). In taxonomic β-diversity, the species turnover of herbaceous and woody were 0.842 (94.08%) and 0.825 (94.83%), whereas species nestedness accounted for only 0.053 (5.92%) and 0.045 (5.17%), respectively ( Figure 5A ). In phylogenetic β-diversity, the species turnover of herbaceous and woody were 0.912 (97.33%) and 0.875 (96.05%), whereas species nestedness accounts for only 0.025 (2.67%) and 0.036 (3.95%), respectively ( Figure 5B ).

Figure 5 The taxonomic (A) and phylogenetic (B) β-diversity and its composition of the herbaceous and the woody community in the arid and semiarid areas of China.

For herbaceous communities, the taxonomic turnover was related to environmental distance after accounting for spatial effects (Mantel’s r = 0.42, p = 0.001), but it did not depend on the spatial distances when considering the environmental influences (Mantel’s r = -0.14, p = 0.12). Phylogenetic turnover displayed a similar trend, but it was reduced in prominence when considering spatial influences (Mantel’s r = 0.34, p = 0.001) or environmental effects (Mantel’s r = -0.20, p = 0.06). For woody communities, the taxonomic turnover was related to environmental (Mantel’s r = 0.53, p = 0.001) but it was not associated significantly with spatial distance (Mantel’s r = -0.16, p = 0.06). Phylogenetic turnover was significantly correlated with the environment (Mantel’s r = 0.55, p = 0.001) and spatial distance (Mantel’s r = -2.4, p = 0.011).

Environmental and spatial variables explained 33% to 77% of the variation in species turnover ( Figure 6 ). The independent effects of environmental variables accounted for 3% and 7% of the overall variances of taxonomic turnover and phylogenetic turnover, respectively. Independent spatial effects accounted for 3% and 2% of overall variances of taxonomic turnover and phylogenetic turnover ( Figures 6A, C ). In comparison, environmental variables (24% for taxonomic turnover and 12% for phylogenetic turnover) were drastically higher than that spatial variables (4% and 3%) ( Figures 6B, D ). Compared to the pure effects, their combined effects accounted for most of the turnover variation in herbaceous (27% for taxonomic turnover and 36% for phylogenetic turnover) and woody (50% for taxonomic turnover and 53% for phylogenetic turnover) species ( Figure 6 ).

Figure 6 Venn diagram displaying the relative importance of environmental filtering and dispersal filtering on herbaceous (A, C) and woody (B, D) species turnover in the arid and semiarid areas of China.

Elevational patterns and drivers of herbaceous and woody in drylands

The species richness of the woody community peaked at mid-elevation areas and declined toward both sides of elevation gradients ( Figure 2B ), supporting the earlier studies in the Helan Mountains ( Zhu et al., 2009 ). The authors attributed the findings to serious drought (low altitude) and lower temperatures (high altitude) with low species richness, and highlighted that the humped pattern of species richness was explained by the moderate climatic situation in the mid-elevations ( Zhu et al., 2009 ). Meanwhile, this result is consistent with previous research on elevational gradients in other mountain habitats ( Zhou et al., 2019 ), which revealed a unimodal relationship. The low richness at lower altitudes might be explained by anthropogenic disturbances and the extreme competition for resources ( Sproull et al., 2015 ; Zhang et al., 2016 ). On the contrary, the poorer richness at higher altitudes might be explained by the ecophysiological limitations of the harsh environment ( Zhu et al., 2009 ; Luo et al., 2019 ), in which their growth was hampered and led to poor biodiversity ( Ding et al., 2022 ; Hu et al., 2022 ). Another possible reason was that abiotic filtration imposed a limit on the seed settlement or species persistence ( Montano-Centellas et al., 2021 ; Wang et al., 2021 ). In other words, water scarcity reduces species richness at lower altitudes, and low temperatures limit species richness at higher altitudes. In comparison, the greater number of species in mid-elevation regions might be mainly related to favorable climatic conditions (e.g., water availability, optimal temperature) in these regions. This means that pressures are strong at both ends of the elevational gradient, but environmental conditions are milder at mid-elevations and therefore species richness is higher at mid-elevations ( Lopez-Angulo et al., 2018 ).

Unlike woody richness, herbaceous richness showed an increasing tendency along elevational gradients. A study in a subtropical forest supported the pattern that plant species richness increased with elevation ( Zhang et al., 2021 ). They suggest that both human activities and the elevation range described by the study are two key factors leading to the observed diverse patterns ( Macheroum et al., 2021 ; Zhang et al., 2021 ; Muhammad et al., 2022 ). In the Helan Mountains, plant communities at high elevations are predominantly herbaceous, whereas those at low elevations are mainly composed of woody plants ( Jiang et al., 2007 ; Pang et al., 2013 ). The study reported that environmental conditions were generally more beneficial for alpine plants, which seem to have essential roles in herbaceous plants ( Yakimov et al., 2020 ). When compared to species at lower elevations, alpine meadow plants without woody constraints use different survival strategies in harsh environments, such as investing more resources in reproductive and below-ground components and expanding display areas to attract pollinators ( Wang et al., 2021 ). Therefore, the shorter life cycle of herbaceous plants and the higher potential for seed dispersal and germination strategies that favor survival may be the main contributors to changes in herbaceous richness across elevational gradients in the Helan Mountains. Furthermore, our findings demonstrate the combined effect of biotic and abiotic stresses on herbaceous species distribution and support the inconsistent trends of herbaceous and woody richness along altitudinal gradients. Notably, our results appear contrary to the widely reported view that elevational trends of species richness should decrease in a unimodal or monotonic pattern ( Lee and Chun, 2015 ; Sproull et al., 2015 ; Zhou et al., 2019 ). However, when drought is exacerbated at lower elevations, it might reduce species diversity and likely produce unexpected biodiversity patterns ( Lopez-Angulo et al., 2018 ). In addition, given the short lifespan of herbaceous plants, especially annual herbs, we may have overlooked species coexistence patterns associated with them due to the fact that we used only one field survey. Therefore, such limitations should be taken into account when interpreting our results. Huang et al. (2016) emphasize that it is essential to pay more attention to herbaceous plants in biodiversity conservation. So, we suggested that more research be done to discover their general distribution in the dryland mountains.

In addition, this study found that both the SESmpd and SESmntd of herbaceous communities significantly increased linearly along the elevational gradient. Still, there is no clear pattern in the phylogenetic structure of woody communities. This difference can be traced to disparities in the responses of various plant functional groups toward climate change, topographic heterogeneity, soil nutrients, and disturbances along the altitudinal gradient in mountainous areas ( Paz et al., 2021 ). In the Helan Mountains, elevation, local conditions, slope, and aspect were reported to strongly influence spatial patterns of plant biodiversity ( Jiang et al., 2007 ; Pang et al., 2013 ). Compared to woody species, herbaceous plants were significantly constrained by multi-dimensional variables (e.g., climatic, aspect, and woody cover), indicating that the effects of various environmental factors on different groups of life forms were inconsistent ( Loidi et al., 2021 ). Such variations probably relate to differences in longevity and tolerance to weather ( Qian et al., 2014 ). Large differences in life cycles and tolerance to climatic stress between herbaceous and woody plants may result in inconsistencies in diversity distribution patterns across elevations ( Qian et al., 2014 ). Herbaceous plants are generally able to adjust to novel climate situations two to ten times quicker compared to woody plants due to their shorter reproductive cycles and faster growth rates ( Smith and Beaulieu, 2009 ; Zhou et al., 2019 ). Moreover, their seed germination, dispersal, and establishment may be tightly controlled by climate and other environmental factors ( Wang et al., 2021 ). In our study, after controlling for other variables, herbaceous richness showed a negative correlation with woody cover, which could be that woody species act as a limiting factor in the species composition of herbaceous communities through the reduction of available resources such as light and soil ( Sproull et al., 2015 ). Therefore, herbaceous and woody assembly processes may be driven by different mechanisms ( Luo et al., 2019 ). We suggest that the herbaceous communities are radically distinct from woody communities concerning the phylogenetic structure ( Qian et al., 2014 ), mainly attributed to abiotic and biotic factors ( Gao et al., 2017 ). In mountainous areas that have been grazed and logged for a long time, different results may be found ( Dainese et al., 2015 ; Wang et al., 2019 ). Therefore, more field experiments in the mountain region are required to validate the above hypothesis.

Although the taxonomic and phylogenetic patterns of elevation distribution of herbaceous and woody plants were not consistent, our study indicated ( Figure 3 ) that most herbaceous and woody communities showed phylogenetic clustering (both SESmpd and SESmntd < 0) throughout elevation gradients. Another important finding was that the phylogenetic structure of most communities did not differ significantly from that expected from the expected null model. We believe that this phylogenetic pattern might stem from deterministic and stochastic processes. Environmental filters played a big role in the phylogenetic clustering of SESmpd, which had a big impact on the whole lineage ( Zobel and Scheiner, 2016 ). However, the SESmntd might result from the decentralization capability of contemporary species ( Volis and Bohrer, 2013 ). In the Helan Mountains, drought has likely filtered out species that lack drought tolerance mechanisms. Preliminary research has shown that strong environmental filtering procedures are more likely to form community assemblages at high altitudes than competitive exclusion procedures ( Chun and Lee, 2017 ). Other studies support that herbaceous species may be subject to assembly processes ( Luo et al., 2019 ), such as dispersal limitation due to their smaller body and fruit size ( Jiang et al., 2015 ). Moreover, the stochasticity may promote the early assembly of plant communities due to the limitations of seeds ( Farjalla et al., 2012 ). Apparently, niche-based and random processes may play a big role in how plants are put together in the Helan Mountains.

Ecological drivers of species turnover

Here we found a comparatively high taxonomic and phylogenetic species turnover of herbaceous and woody communities in the Helan Mountains flora ( Figure 5 ), which is consistent with research in Donglingshan Mountain ( Yakimov et al., 2020 ). Although herbaceous and woody plants exhibit a higher taxonomic and phylogenetic turnover, they correlated poorly with spatial distance after controlling for environmental effects. As previous studies have shown, an environmentally heterogeneous ecosystem generally has a relatively high turnover rate ( Coelho et al., 2018 ). Species turnovers tend to increase with environmental heterogeneity due to amplified variations in community composition and species richness ( Ahmad et al., 2020 ). There is an evident species substitution phenomenon in this highly heterogeneous mountain ecosystem due to regional environmental differences ( Bergamin et al., 2017 ). In addition, turnover is related to elevation and may also be influenced by soil fertility, water resources, meteorology, and light conditions ( Dainese et al., 2015 ; Nascimbene and Spitale, 2017 ).

This study found that independent contributions of spatial and environmental factors differentially influenced taxonomic and phylogenetic turnovers of herbaceous and woody species ( Figure 6 ). The reason could be that herbaceous and woody plants differ in their evolutionary relationships and dispersion patterns ( Liu et al., 2015 ). Studies show that woody plants are both less plastic in their basic niche and more dispersal-selected than herbaceous plants ( Farjalla et al., 2012 ). Our study area’s topographic structure may have resulted in significant geographic isolation, limiting the migration, dispersal, and assemblage of many of the species distributed in the current forest. Further, canopy structure might more intensely influence understory plant (herbaceous) composition ( Luo et al., 2019 ). Consequently, they probably followed relatively independent pathways in terms of evolution, dispersal filtering, and species interactions. We also found that the joint contribution of spatial and environmental factors had the highest proportion in explaining the turnover of herbaceous and woody plants ( Figure 6 ). This result means that the spatial turnover of plant communities in our study area is mainly shaped by a combination of EF and DF ( Chun and Lee, 2017 ; Grigoropoulou et al., 2022 ). As emphasized by previous studies, our results support the view that EF and DF jointly control plant community assembly, although the relative contribution of these two processes at different areas and scales is still inconclusive ( Shi et al., 2021 ). It is worth noting that herbaceous and woody species are constantly interacting. Woody species can act as a filter in the structuring of understory plants (herbaceous) by reducing resource availability ( Luo et al., 2019 ), but the sampling design of this study did not proceed according to plant-plant interactions, which would not directly capture the effect of woody plants on herbaceous plants. Nevertheless, integrating the taxonomic and phylogenetic diversity of herbaceous and woody species might provide a novel insight into the flora assemblage in the arid and semi-arid mountains.

Implications of biodiversity conservation

As a crucial dimension of biodiversity, beta diversity could offer important evidence to predict ecosystem functioning and improve protected priorities ( Martinez-Almoyna et al., 2019 ; Scriven et al., 2015 ). Furthermore, knowledge of beta diversity patterns may effectively shape preservation policies ( Swenson, 2011 ; Bergamin et al., 2017 ). For example, if species turnover is the dominant pattern, more protected areas are needed for biodiversity conservation ( Arif et al., 2022b ; Hira et al., 2022 ). However, when nestedness is the prevailing pattern, there is a need to establish a sufficiently large protected area with high species richness ( Bergamin et al., 2017 ). Given that species turnover in the Helan Mountains is the dominant factor in driving the β-diversity pattern ( Figure 5 ), conservations must focus on a vast number of protected areas distributed to provide maximum protection for the life forms of species ( Bergamin et al., 2017 ; Muhammad and Changxiao, 2022 ). Increasing evidence suggests that phylogenetic diversity is a key to understanding species assemblages and might lead to a fundamental understanding of ecosystem function ( Li et al., 2020 ). Phylogenetic diversity represents the lineage evolution relationships among species and it can help form conservation strategies, it may be more important to conserve a phylogenetically unique species, compared to a more redundant one. Furthermore, our results suggest that both environmental and spatial factors play an important role in shaping plant community assembly, and therefore, it is desirable to combine environmental filtering with dispersal limitation in the practical process of biodiversity conservation in drylands. As a consequence of climate change, the extent of global dryland area is projected to increase particularly in developing countries, which further increases dryland degradation and biodiversity loss ( Huang et al., 2015 ). The global decline in biodiversity has driven calls for ambitious targets for biodiversity conservation and protected areas coverage ( Peng et al., 2021 ). Thus, our findings could have a big impact on the conservation of biodiversity in drylands as the climate warms and causes more drought ( Zhu et al., 2020 ; Jiao et al., 2021 ).

Conclusions

In summary, this study integrates TD, PD, and environmental drivers to evaluate herbaceous and woody species’ general patterns and assembly mechanisms along elevation gradients in arid and semi-arid regions. Our study demonstrated that the responses of herbaceous and woody plants along elevation gradients in the Helan Mountains are decoupled mostly due to the inconsistent influence of biotics and abiotics on them. The TD and PD of herbaceous communities substantially increase linearly along an elevational gradient, while a nonlinear model was remarkable for woody communities with relatively low richness at the ends of the elevation range and peaked richness at mid-altitudes. In addition, there was no relationship between woody PD and elevation. We found TD and PD were mainly dominated by species turnover with fewer contributions from nestedness. The turnover process is primarily caused by a combination of environmental and spatial variables. We also showed that environmental and dispersal filtering jointly shapes the plant community assemblages along elevational gradients in arid and semi-arid areas. These findings highlight that conservationists and policymakers should focus on the different adaptation strategies of herbaceous and woody plants to the drought that continues to increase with global warming.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding author.

Author contributions

Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Visualization, Writing - original draft, Writing - review, and editing were performed by JZ. Methodology, Software, Validation, Formal analysis, Investigation, Writing - review, and editing was performed by MA. Investigation, Writing - review, and editing were performed by XH and DD. Validation, Writing - review, and editing were performed by SZ. Investigation, Formal analysis, Data curation was performed by XN. Investigation, Resources, Writing - review and editing, Supervision, Project administration, Funding acquisition were performed by CL. All authors contributed to the article and approved the submitted version.

This work was supported by Ningxia Key Research and Development Project (No. 2020BFG03006, 2021BEG02005); Ningxia Natural Science Foundation Project (No. 2020AAC03107); Chongqing Municipality Key Forestry Research Project (No. 2021-9); Chongqing Municipality Housing and Urban Construction Committee (No. Chengkezi 2019-1-4-2); Forestry Extension Project of China Central Finance (No. Yulinketui 2020-2); Science Foundation of College of Life Sciences of Southwest University (No. 20212005406201).

Acknowledgments

We are grateful to Mr. Zhu Qiang and Mr. Wang Jifei for their technical and field support during data collection. Finally, we want to express our profound gratitude to Mr. Yan Lingbing for his immeasurable support.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpls.2022.1041742/full#supplementary-material

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Yakimov, B. N., Gerasimova, A. S., Zhang, S., Ma, K., Zhang, Y. (2020). Phylogenetic α- and β-diversity elevational gradients reveal consistent patterns of temperate forest community structure. Acta Oecol. 109, 103657. doi: 10.1016/j.actao.2020.103657

Yuancai, Q., Arif, M., Dong, Z., Ting, W., Qin, Y., Bo, P., et al. (2022). The effect of hydrological regimes on the concentrations of nonstructural carbohydrates and organic acids in the roots of Salix matsudana in the three gorges reservoir, China. Ecol. Indic. 142, 109176. doi: 10.1016/j.ecolind.2022.109176

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Keywords: dryland, community assembly, taxonomic diversity, phylogenetic diversity, Helan Mountain Nature Reserve

Citation: Zheng J, Arif M, He X, Ding D, Zhang S, Ni X and Li C (2022) Plant community assembly is jointly shaped by environmental and dispersal filtering along elevation gradients in a semiarid area, China. Front. Plant Sci. 13:1041742. doi: 10.3389/fpls.2022.1041742

Received: 11 September 2022; Accepted: 14 November 2022; Published: 25 November 2022.

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Copyright © 2022 Zheng, Arif, He, Ding, Zhang, Ni and Li. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Changxiao Li, [email protected]

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Plant Strategies and the Dynamics and Structure of Plant Communities. (MPB-26), Volume 26

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Community Gardening: Stress, Well-Being, and Resilience Potentials

Way inn koay.

1 Department of Psychology, James Cook University Singapore, Singapore 387380, Singapore; [email protected]

2 Department of Psychology, Singapore General Hospital, Singapore 169608, Singapore

Denise Dillon

The financial and health burdens of stress associated with increased urbanization have led to a demand for mental health enhancement strategies. While some extant literature details mental health benefits of community gardening, a coherent narrative on the construct of resilience and its relationship with the mental health benefits of community gardening is lacking. The present study examined the relationship between community gardening and a number of mental health benefits, in the forms of subjective well-being, stress, resilience potentials, and resilience factors (self-esteem, optimism, and openness). A total of 111 residents in Singapore completed a survey. Results from Multivariate Analysis of Covariance (MANCOVA) and Pearson’s correlation analyses show that, after controlling for age and levels of connection to nature, community gardeners reported significantly higher levels of subjective well-being than individual/home gardeners and non-gardeners, indicating that engagement in community gardening may be superior to individual/home gardening or non-gardening outdoor activities. Community gardeners reported higher levels of resilience and optimism than the non-gardening control group. These novel results indicate some potential for mental health benefits in urban environments, specifically in terms of subjective well-being and resilience. These findings have implications for future research in clinical psychology, mental health promotion, and policy.

1. Introduction

It is commonly accepted that stress varies on a continuum from maladaptive responses to acute or enduring anxiety to more severe stress reactions that negatively impact general well-being and daily functioning, depending on individual vulnerability and resilience potentials. Abundant research findings have evidenced that stress is associated with poor mental and physical health (e.g., depression, cardiovascular disease) [ 1 , 2 , 3 ]. The cumulative effects of daily stressors are also found to be an important predictor for the emergence of depression, which is found to be the most common mental disorder in Singapore with a lifetime prevalence of 5.8% [ 4 ]. Stress has also been found to be associated with overall lower well-being [ 5 ] and incurs costs on society [ 6 , 7 ]. Hence, there is an ongoing need for low-cost and effective strategies to enhance mental health by lessening the impact of stress or promoting well-being, particularly in Singapore.

Recent shifts in societal views and research findings have shown that community gardens have ample potential to provide spaces for individual and communal good, and to contribute to community bonding, health and urban-environmental equilibrium that many in Singapore and the world are yearning for. Consequently, there is a rise in the emergence of community gardens across cities, including Singapore. Congruent with the evolution of the National Parks of Singapore’s (NParks) vision of Singapore from “Garden City” to “City in a Garden” [ 8 ], the Singapore government has allocated substantial funding for a range of initiatives. These include establishing world-class gardens, optimizing urban spaces for greenery, enhancing community gardening movements, and incorporating community gardens as vital aspects of urban design and city planning [ 9 , 10 ]. The Community in Bloom (CIB) initiatives, launched in 2005 by NParks [ 11 ], have fostered nearly 1000 community gardens nationwide and inspired a community spirit amongst residents to co-achieve Singapore’s “City in a Garden” vision. The funding is distributed for the maintenance of the community gardens and for horticultural assistance. Given the substantial funding invested, it is important to determine if the current Singapore community garden movements have the potential for sustainability and to identify their effects on the mental health of residents in Singapore. Hence, the existing literature on the benefits of connection to nature and gardening activities, in combination with current data on community gardening activities, needs to be examined to demonstrate the patterns of contribution (e.g., in terms of nature or social elements) of community gardening in Singapore in a clearer way. While literature on the benefits of community gardening in Western countries (e.g., U.S.A. and U.K.) is available, there is a scarcity in the literature focusing on benefits stemming from community gardening activities in Eastern-oriented countries, such as Singapore.

In view of the significant health and financial burdens of stress and depression on the individual and society, the substantial funding invested in community garden initiatives, the potential benefits of community gardening to mental health, as well as the scarcity in the research literature specific to Singapore, the current study is both relevant and timely.

As a beginning, evidence of the effects of natural environments (or green space) and gardening activities on mental health is first reviewed. Subsequently, the focus is shifted to community gardening alone, followed by a review of the restorative properties of natural environment and a discussion of existing evidence of the effects of community gardening on mental health (e.g., well-being and stress). The final section evaluates the future prospects and other potential benefits of community gardening by analyzing its relationships with resilience and resilience factors respectively. The literature review helps shape the hypotheses critical to answering specific research questions.

1.1. Restorative Properties of Natural Environments

Two theories have been expansively cited in the literature to underpin the associations between the restorative properties of natural environments and recovery from stress and mental fatigue, suggesting mental health benefits—the psycho-physiological stress reduction framework [ 12 ] and the Attention Restoration Theory (ART) [ 13 , 14 ].

According to the psycho-physiological stress reduction framework [ 12 ], humans are biologically attuned through evolution for immediate positive responses to safe, natural environments associated with survival, such as trees, vegetation, and water. Thus, exposure to natural stimuli can support restoration from stress, which includes recovering from markedly high or low physiological and psychological conditions and recharging of the energy consumed in response to stress [ 15 ]. Exposure to natural environments can also mediate the destructive effect of stress by reducing negative mood while enhancing positive affects [ 15 , 16 ]. This restoration-from-stress effect can be gained through the activity of gardening, and this is empirically supported by the results of a field experiment in which mood was found to be restored, and stress levels, as assessed by cortisol levels, were found to reduce with the strongest extent following gardening, as compared to a control group [ 17 ]. A longitudinal survey with empirical data also indicated that adults who moved to greener residential areas benefitted from sustained improvements in their mental health, supporting the restorative effects of natural environments [ 18 ].

Meanwhile, according to the ART [ 14 ], humans have a predisposition to respond positively to the contents and features of natural environments (e.g., green landscapes) and have a preference for scenes depicting natural rather than urban environments because of the cognitive restorative effect. Berman, Jonides, and Kaplan [ 19 ] employed an experimental design to review the cognitive benefits of interactions with natural environments compared to urban environments. The improved directed-attention abilities after interacting with nature validated the ART. The cognitive restorative effect, as evidenced by improved performance on tasks involving attention and cognitive processing following visual exposure to natural environments [ 20 , 21 ], helps to restore an individual’s voluntary or directed attention, which in turn reduces mental fatigue. By reducing mental fatigue that manifests itself in negative emotions, the probability that individuals experience a stress response due to cognitive overload is reduced simultaneously.

Both theories highlight that exposures to natural environments are more restorative (e.g., provide physiological, emotional and attention restoration) than urban environments [ 22 ]. Inability to restore attentional capacity aggravates the mental fatigue state and can also threaten well-being and mood, as well as affecting work performance and interpersonal relationships. Thus, individuals who are deprived of exposure to natural environmental features will exhibit behaviors caused by mental fatigue.

1.2. Effects of Natural Environments and Gardening Activities on Mental Health

Humans depend both physically and emotionally on nature [ 23 ], and both spending time in nature and connection to nature were observed to offer a number of cognitive, effective, and physiological benefits [ 24 ]. Measures such as the Inclusion of Nature in Self (INS) scale [ 25 , 26 ], the Connectedness to Nature scale [ 27 ], and the Nature Relatedness scale [ 28 ] all capture expressions of the same construct: a subjective connection to nature [ 29 , 30 ]. Exposure and connection to natural environments not only has direct benefits through stress recovery and mental fatigue restoration, it also has implicit benefits by serving as a buffer against stressful life events [ 17 ]. Regular contact with nature is also found to lead to long-lasting, positive impacts on mental health, including a reduction in depressive and anxiety symptoms [ 31 ]. Landscapes consisting of natural elements (e.g., groves of pine) have been found to evoke feelings of pleasure and calmness, and are conducive to restoration from stress [ 32 ]. Green spaces in urban environments are associated with stress relief [ 33 ] and longevity for senior citizens [ 34 ]. On the other hand, stress has been found to be a mediator of the relationship between neighborhood greenery and mental health [ 35 ]. In addition, loneliness, perceived decreased social support, and stronger social cohesion have been shown to partially mediate the relationship between greenery and mental health [ 35 , 36 ].

Established evidence has supported the benefits of gardening activities, one form of exposure to natural environments. Kaplan [ 37 ] initiated groundbreaking research by employing interview and questionnaire approaches to investigate the psychological benefits of home/individual gardening and community/plot gardening. The findings show that gardeners rated gardening as a valuable means by which to spend time, relax, and gain a sense of accomplishment. Subsequently, gardening activities have been widely studied as potential methods of restoration from stress and negative mood, or as therapeutic interventions (e.g., horticultural therapy) for people suffering mental health-related difficulties (e.g., [ 38 , 39 , 40 ]). Significant reductions in stress, fatigue and depressive symptoms in the context of gardening activities have also been reported [ 41 , 42 ]. Recent meta-analytic research documents considerable evidence for the positive effects of gardening on both physical and mental health, after adjusting for publication bias [ 43 ]. Increasing research reflects a broader interest in the role of different forms of gardening activities (e.g., home gardening, community gardening) in enhancing mental health respectively.

1.3. Community Gardening

Community gardening generally refers to activities ranging from multiple individual plots to collective cultivation at a common space—a school or a hospital, in a public space or a neighborhood. The origin of community gardening in the United States can be traced to the late 1800s when abandoned gardens were opened to the urban unemployed to grow food [ 44 ]. The allotment garden is a sub-type of the more general category of community garden and its origins can be traced to Europe in the 18th century when parcels of land were open to deprived plot holders and their relatives to cultivate food [ 45 ]. In Singapore, community gardens are described by the National Parks Board [ 46 ] as “common spaces where people of different demographics come together to create, develop and sustain a gardening space in their locality”.

Community gardening, a form of exposure and connection to natural environments, emerges as a complex multi-factorial activity that involves collective effort by the community to cultivate plants. Community gardening is recently getting much more research attention because of its direct and indirect impacts on individual mental health and its potential contribution to community bonding and building a sense of community [ 47 ]. It benefits the gardeners themselves and the broader community by supplying food, high-quality nutrition, recreation opportunities, and physical activities within neighborhoods, offering a way to restore connection with nature, and contributing to restoration of ecological connection [ 44 , 48 , 49 , 50 ]. Community gardening has been reported to have positive effects on mental health due to the direct contact with natural environments it affords to community gardeners and its tranquil, restorative, and social nature [ 47 , 51 , 52 ]. Gardeners described involvement in a community garden at Alabama as stress-relieving and relaxing, suggesting mental health benefits [ 53 ]. Community gardening has also been discussed as a further mechanism to explain beneficial effects from nature for coping with daily stress [ 54 ]. Community gardeners reported that they valued the garden as a personal achievement, suggesting community gardening is associated with pride and well-being [ 53 ]. Lovell, Husk, Bethel, and Garside [ 55 ] recently conducted a mixed method systematic review and this study is the first systematic review, which has highlighted the health and well-being benefits of community gardening for children and adults. They suggested the mechanisms and different levels of operation through which community gardening may impact health and well-being. Overall, the benefits of community gardening on individual mental health and community cohesion are evident.

Empirical research studies with quantitative data on the mental health benefits of community gardening are relatively scant. Two empirical studies show that participants reportedly gained psychological benefits relating to quality of life including reduced stress levels, improved self-esteem, and increased social interaction, after taking part in community gardening [ 51 , 56 ]. In a study conducted by Wakefield, Yeudell, Taron, Reynolds, and Skinner [ 57 ], which employed participant observation and in-depth interviewing approaches to collect data, the findings showed that community gardeners perceived the community garden as a place offering positive social interaction, improved mental health and increased physical activity, suggesting associations between community gardening and community cohesion. The findings of a recent study in China indicated that participation in a community gardening benefits people’s mental health experience [ 58 ], which likely contributed by the improved social exchange among community residents and proximity to nature. A limitation of the study is that mental health was measured with only two items and mental health benefits were not explored in specific forms.

1.4. The Relationship Between Community Gardening and Individual Constructs

Under the perspective of policy makers, researchers, or community gardeners, the benefits of community gardening are commonly categorized into a more general and unified category—the mental health benefit. Here we review and distinguish the individual, specific features within the mental health benefit.

1.4.1. Well-Being

The construct of well-being and the proposed pathways to its attainment have generally been conceptualized according to two philosophical perspectives: hedonia and eudaimonia [ 59 , 60 ]. Past dispute pertaining to the pursuit of well-being culminated in an agreement that both hedonic and eudaimonic perspectives are divergent and contribute to well-being in distinctive manners [ 61 ]. Based on the hedonic perspective, well-being is composed of one’s perceptions of pleasantness and is attained though the maximization of pleasurable moments and the satisfaction of one’s desires [ 62 ]. The hedonic perspective considers well-being as subjective evaluations about the quality of one’s life, which, in turn, are translated and operationalized into the construct of subjective well-being [ 63 ]. Subjective well-being consists of an affective component with higher prevalence of positive emotional experiences over negative emotional experiences, and a cognitive component focusing on a personal judgment on the satisfaction level with life and with specific life domains respectively [ 63 , 64 ]. Meanwhile, based on the eudaimonic perspective, well-being is about pursuing individual values or meanings in life and is attained through fulfilling an individual’s inherent potential for personal growth [ 65 ].

The literature on well-being is broad, and the construct of subjective well-being has been extensively studied. Of interest to the current study is the recent resurgence of interest in contact with natural environments and its ties with well-being [ 66 , 67 ]. Studies have recorded that contact with natural environments and connection to nature are associated with affective well-being, such as enhancing happiness [ 68 , 69 , 70 , 71 , 72 ]. A meta-analysis even proposed quantitative evidence on the positive links between nature connectedness and happiness as an important affective component of subjective well-being [ 29 ]. Since gardening is one of the conventional approaches of interacting or connecting with nature, there is an increasing slant towards research that examines the links between gardening activities and happiness, or subjective well-being. Horticultural and physical activities, such as gardening have been investigated and found to result in positive effects in terms of well-being and self-esteem [ 73 ]. A pilot pre- and post-test study conducted by Heliker, Chadwick, and O’Connell [ 74 ] documented an improvement in subjective well-being, feelings of satisfaction and spiritual well-being of elderly participants (age range 63–90) as a consequence of involvement in a gardening project comprising twelve classes covering educative topics like propagation techniques, terrariums, and planting herbs. However, the limitation of this study is the lack of a no-treatment control group for the comparison of the effects of gardening. In a survey study, home gardening was found to be positively correlated with improved mental health and well-being [ 75 ]. Adolescents who did home gardening reported fewer depressive symptoms and improved emotional well-being than those who did not do gardening.

Both home gardening and community gardening include the elements of connection to nature, and gardening experience. Community gardening is different from home gardening because of its additional social element as well as its gardening locations [ 76 ], and gardening with others often leads to increased socialization and responsibility to the group [ 77 ]. Thus, there is a shift towards investigating the importance of community gardening in maintaining or enhancing subjective well-being that involves the preponderance of pleasant affect over unpleasant affect [ 63 ]. Given that social relatedness has been found to predict happiness or subjective well-being [ 78 ], it is reasonable to expect that community gardening should have at least comparable effects to home gardening on subjective well-being.

Milligan, Gatrell, and Bingley [ 79 ] conducted a study employing primarily ethnographic methods and found that communal gardening activities enabled older community gardeners (aged over 60 years) to acquire subjective well-being in the forms of a sense of achievement, pleasure, satisfaction and enhanced quality of life. Most of the older adults opted to garden communally with others on the allotment sites, in turn reducing social isolation that can serve as a buffer to stressors. The study results have supported the potential, specific benefits of communal gardening over and above the contribution of the traditional ‘isolated’ gardening to health and well-being of older adults. Austin, Johnston, and Morgan [ 80 ] conducted a pilot study employing a one-group (age range 57–78 years), pre-test/post-test design to examine the effects of participation in a community gardening program on the participants’ functional health, depression, and physical fitness. Their results indicated a decline in negative emotions and distress following gardening activities.

Kingsley, Townsend, and Henderson-Wilson [ 81 ] employed a qualitative semi-structured interviewing approach to elicit responses from community gardeners (age range 20–69 years) in order to have greater insight into their understanding and perceptions of health and well-being benefits following their engagement on the ‘Dig In’ community garden in Melbourne. The community gardeners described that they experienced enhanced well-being because the community garden offers a sense of achievement, enables them to feel closer to nature and offers a getaway from daily stresses. Van den Berg et al. [ 17 ] conducted a survey among gardeners with a mean age of 59.6 years from 12 allotment sites in the Netherlands and their neighbors as the control group, and the survey questionnaires included questions about their health, well-being with four components (i.e., amount of stress, life satisfaction, loneliness, and social well-being) and physical activity. The results further support the contribution of community gardening activities on well-being, as evidenced by the higher scores of the older gardeners on health and subjective well-being measures compared with those of the control group. A case-control study showed that 136 gardeners with a mean age of 55.8 years who engaged in allotment or community gardening reported higher levels of mood and self-esteem, and a reduced level of psychological distress as compared with 133 non-gardeners [ 82 ].

In summary, these research findings imply that community gardening has positive benefits on gardeners’ mental health through a contribution to the different aspects of well-being, such as increased levels of positive affect and improved life satisfaction.

1.4.2. Stress

Accumulating research studies supply evidence for the benefits of community gardening on stress rejuvenation and well-being. The construct of stress can be defined as difficult life events or chronic hassles and stressors that are non-pleasant to the extent of threatening the well-being and existence of the respective individual [ 83 ]. Higher relaxation is also deemed a vital component of well-being [ 84 ]. Perceived stress can also refer to a composite measure of the extent and amount to which one’s life situations are appraised as stressful [ 85 ].

Similar to the construct of subjective well-being, the construct of stress has been extensively studied. Of interest to this study is the established finding that stress and adverse life events negatively impact mental health, and many studies document that stress precipitates negative psychological symptoms [ 86 , 87 ]. In view of the negative effects of stress, much research has been dedicated to discover adaptive and effective coping strategies for stress. The beneficial effects of nature on stress have been examined thoroughly, and visiting gardens, which provide exposure to nature, has been advocated as a perceived stress reduction strategy [ 83 ]. Research findings indicate that access to green spaces has been associated with restoration from stress, greater social capital, more positive emotions, and an increased sense of well-being [ 88 ].

The impacts of community gardening on mood and stress are highlighted by a study evaluating the community gardening programs at some of California’s domestic violence shelters [ 89 ]. Stuart employed survey and structured interviewing approaches with 81 program participants. Her findings show that gardening eased adjustment to the domestic violence shelter and relieved stress upon seeing new growth of plants. In the study by Wakefield et al. [ 57 ], the community gardeners indicated merely being present and belonging to a community garden helped relieve stress, as evidenced by quotes such as: “… sometimes when you are stressed out… when you go to the garden, you feel different.” (p. 97). This point was echoed in a study conducted by [ 81 ] in which a community gardener indicated that the “garden has a lot of things going for people who are in stressful environments of today and who want to get away from these pressures.” (p. 211). A study in Australia applying semi-structured interviews also showed that stress relief was one of the motivations for community gardening participation [ 90 ], but such qualitative insights need to be supported by quantitative data.

Hawkins, Thirlaway, Backx, and Clayton [ 91 ] conducted a cross-sectional study to investigate the contribution of communal gardening activity at an allotment site on the perceived stress amongst participants (age range 50–88 years). The participants were categorized into four groups with different levels of physical activity and contact with nature: allotment gardeners, home gardeners, participants who performed outdoor physical activity via health walks and participants who performed indoor physical activity. The results showed significantly lower levels of perceived stress for the allotment gardeners than participants who performed indoor physical activity. However, there was no significant difference in the perceived stress levels between the allotment gardeners and home gardeners, or those who performed outdoor physical activity.

1.4.3. Resilience

Due to the shift from the “problem-oriented” paradigms of psychopathology toward “strength-based” paradigms where the focus is on adaptive coping despite stress and adversities, researchers subsequently bring the construct of resilience into the spotlight by investigating the resilience-stress relationships and well-being. Many studies propose that, when individuals experience stressful life events, their positive assets such as trait resilience and self-efficacy can be activated to support them for successful adaptations and active coping [ 92 , 93 , 94 ]. Perceived stress has also been illustrated to have a negative correlation with resilience [ 95 ]. As adaptive coping is associated with mental health [ 96 ], it is relevant to review the construct of resilience and its relationship with community gardening in order to get a clearer picture of the mental health benefits of community gardening.

Literature has demonstrated that resilience is broadly acknowledged as a multidimensional construct with a few common fundamental components amidst the diversity [ 97 , 98 , 99 , 100 , 101 ]. The construct of resilience can be employed to illustrate the ability to bounce back from stress to optimal levels of well-being [ 102 , 103 ]. Alternatively, resilience refers to the ability to enable individuals to adapt to hardships or the ability to enable individuals to adapt well to stressful situations [ 104 , 105 ] and the ability to deal with shocks and unexpected changes [ 106 ].

Windle [ 107 ] employed the integrated methods of systematic review, concept analysis, and face-to-face consultation to offer a reality-driven perspective of attributes and consequences of resilience. According to Windle, resilience is defined as follows:

A process of negotiating, managing, and adapting to significant sources of stress or trauma. Assets and resources within the individual, their life, and environment facilitate this capacity for adaptation and ‘bouncing back’ in the face of adversity. Across the life course, the experience of resilience will vary (p. 163).

Results from past and recent advances of research indicate that individual resilience is connected with multiple mental health-related outcomes such as self-reported levels of stress, burnout, and general indicators of well-being [ 108 ]. The moderating effect of resilience in the links between stressful life events and late-life depression appears to be such that resilience could perform as a buffer against the detrimental mental health impacts of stressful life events [ 109 ]. Given the resilience-stress relationships, and that natural elements are associated with the reduction of mental fatigue and psychological stress, engagement in community gardening should also be helpful in increasing resilience from stress and leading to significant improvements in well-being. However, published research investigating the relationship of community gardening with the construct of resilience is very scarce. A few recent studies suggest it may have potential but most of the relevant literature has been covered under the umbrella of natural environments and green spaces.

Community gardening has been proposed as a means to foster good health and well-being by furthering resilience on three levels (individual, social, and natural environment), strengthening social resilience, and motivating the execution of other neighbourhood improvements, particularly in deprived areas [ 110 , 111 , 112 ]. Okvat and Zautra [ 112 ] reviewed and summarized the relevant evidence for the cognitive, emotional, social network, economic, climate change mitigation and environmental benefits of community gardening to clarify the role of community gardens in promoting resilience in social ecological systems or the Earth community.

The findings of the study conducted by Chawla, Keena, Pevec, and Stanley [ 113 ] extend understanding about the value of community gardening and resilience. They uniquely employed ethnographic observations and interviewing approaches and recruited participants across six study sites covering primary schools and secondary schools. In particular, they conducted interviews with the teen gardeners at two of the six study sites about their gardening experiences in their schoolyards or in an after-school gardening program in which they grew vegetables and herbs collectively, consistent with community gardening activities. The teen gardeners reported feeling relaxed, calm, and peaceful in the midst of and after gardening and provided reasons. Consistent with the past research findings, the results also document that access to nature reduces depression rates and facilitates coping with stress as these participants had numerous chances to expose themselves to positive sensory experiences, and immerse themselves in productive, creative, and cooperative activities. They also find that the natural areas motivated sustained attention and facilitated the development of supportive social relationships, which are an important protective factor for resilience. Thus, it appears that contact with nature created circumstances for enhancing resilience through strategies advocated by Masten and Reed [ 111 ]: building assets (e.g., increasing sense of competency and concentration that contribute to self-esteem), reducing risks (e.g., inattention), and mobilizing adaptational systems (e.g., cooperative friendships). The overall study findings reported by Chawla et al. [ 113 ] connect stress, resilience, and contact with nature as evidenced by the potentials of green schoolyards in reducing stress and enhancing protective factors for resilience in children and adolescents. However, as two of the study sites involved more active community gardening activities compared to the other sites merely with exposure to nature and green schoolyards, research work in further teasing apart the contributions of connection to nature, gardening experiences, and physical or social elements that community gardens possess is required. A literature gap is identified and further work may be required to focus on the different elements of community gardening and their impacts on resilience respectively.

1.5. The Relationship Between Community Gardening and Resilience Factors

Resilience is also found to be fostered with protective factors: individual attributes and qualities and their context, and the relationships with the situations or experiences that predict good adaptation following stress and adversity [ 114 , 115 ]. As a result, resilience can be enhanced through strategies that serve to strengthen individual resilience factors and build assets (e.g., increasing individuals’ concentration that contribute to their self-esteem), reduce risk factors, and mobilize adaptational systems (e.g., friendships and emotional support) [ 111 ]. Windle, Bennett, and Noyes [ 107 ] summarized that resilience is predominantly measured from a multi-level perspective constituted by several key dispositions and factors that influence individuals’ vulnerabilities to risk, stress, and adversities. Some of the common resilience factors and key dispositions are acceptance of change, optimism, self-esteem, personal competence, and social competence. Previous studies also recorded the associations between factors like optimism, self-esteem, self-efficacy, and extroversion, and fewer negative consequences after stress and traumatic events [ 116 ]. Moreover, optimism, the ability to appraise stressful events in less intimidating ways and the capacity to reframe adverse experiences in a positive way have each been found to link with resilience [ 117 , 118 ]. Likewise, Storm and Rothmann [ 119 ] found that openness is correlated with positive re-appraisal of stressful situations and acceptance of stressors. Openness to experience is also found to be associated with problem-solving capacity and creativity, which are deemed integral to resilience [ 120 ]. The resilience factors investigated in the present study are self-esteem, optimism, and openness.

1.5.1. Self-Esteem

Self-esteem is a psychological construct that reflects one’s overall appraisal of one’s value or self-worth [ 121 ]. There is plenty of literature investigating the relationships between self-esteem and subjective well-being and depression [ 122 ]. Contact with nature and gardening have been found to have a positive influence on self-esteem, one of the resilience factors [ 123 , 124 , 125 , 126 , 127 ]. However, Freeman et al. [ 123 ] did not distinguish between home and community gardening as separate aspects, and how they individually influence self-esteem. The research findings of Hoffman et al. [ 125 ] indicate that students who completed a sixteen-week gardening program reported elevated levels of self-esteem and self-efficacy. However, their study was limited by the possibility of biased results originating from a lack of pre-test or baseline condition. Nonetheless, these findings lay the groundwork, which sets the discussion about the association of community gardening with self-esteem. Scott, Masser, and Pachana [ 128 ] employed a survey approach to gather qualitative and quantitative data of older adult gardeners (age range 60–90) from various seniors’ groups and a community gardening group. The qualitative data were assessed by deriving themes using Leximancer text analysis software and the results show the psychological and physiological benefits of regular connection with nature through gardening activities, in their own homes or in community gardening groups. The gardening activities were found to provide the gardeners with the possibility of meaningful activity, which in turn is associated with improved self-esteem and sense of achievement. Again, the participants are clustered collectively under the bigger and more general umbrella of a gardening group, and the mechanisms by which home gardening and community gardening individually influence self-esteem remain unknown.

Only one study appears to have investigated how community gardening individually influences self-esteem. A case-control study investigated the well-being and health benefits of 269 participants, half of whom were community gardeners from 10 allotment sites in England [ 82 ]. The participants were requested to complete a questionnaire about their self-esteem, mood, and general health. Strength of this study was the inclusion of non-gardeners as a comparison control group. The findings indicated that one session of allotment gardening, which is a subtype of community gardening, can give rise to higher levels of self-esteem and mood, regardless of the duration participants spent on gardening. Compared to the non-gardener control group, the allotment gardening group had higher levels of self-esteem and mood, and a reduced level of psychological distress. Nonetheless, further in-depth work may need to be done to investigate how community gardening solely links with self-esteem.

1.5.2. Optimism

Optimism is a construct defining as a generalized inclination to expect and anticipate positive outcomes in one’s life or future events, with pessimism at the opposite end of the spectrum [ 129 ]. People who are optimists tend to report higher subjective well-being because they deal with critical life situations more adaptively than pessimists do [ 130 ]. Optimism may also confer resilience to stressful life events, which are related with a risk of mental disorders [ 131 ]. Positivity about the future outlook relating to optimism seems to afford individuals an element of resilience when faced with adversity [ 132 ].

As engagement in community gardening has been found to influence self-esteem, which is one of the resilience factors, community gardening may have an association with other resilience factors closely linked with self-esteem, such as optimism. To date, only two studies have investigated the link between gardening and optimism. Waliczek, Zajicek, and Lineberger [ 133 ] documented that gardeners responded more positively on statements pertaining to optimism and physical self-concept when compared to responses of non-gardeners. Sommerfeld, Waliczek, and Zajicek [ 134 ] employed the Life Satisfaction Inventory A to investigate participants’ perceptions of life satisfaction and physical activity level. Their results also showed that gardeners gave significantly more positive answers on the quality-of-life statements (e.g., optimism) when compared with non-gardeners. However, as described above, the literature did not distinguish between home (individual) and community (social) gardening as separate aspects, and how they separately influence optimism. Hence, further work may need to be done to investigate how community gardening individually associates with optimism.

1.5.3. Openness

Openness is considered as the broadest and most contentious personality trait of humans, under the Big Five personality dimensions [ 135 ]. Openness is sometimes referred to as change acceptance or positive view of changes [ 136 ], and openness to change values were found to be positively associated with the openness to experience trait [ 137 ]. Over the years, numerous labels for “openness” have been posited. The openness to experience label originated from the work of Costa and McCrae [ 138 ], who found that measures of imagination, intelligence and openness to change had tendencies to co-change. Openness to experience has since been one of the more popular labels capturing “openness” [ 135 , 139 ]. Research findings have documented positive associations between openness to experience and resilience across populations. In addition, a meta-analysis [ 140 ] documented a close relationship between openness to experience and the subjective well-being facets of happiness, positive emotions, and quality of life.

Openness to experience has also been found to be associated with connection to nature, which is one of the elements of community gardening [ 30 , 141 ]. This is not an unexpected finding because change is a constant force in natural environments. As gardening involves change and growth in the cultivation of plants, people who enjoy community gardening should likely have more opportunities to be familiar with experiences of change as either growth or decline. Given that higher levels of acceptance to change are found to have associations with high levels of self-esteem and optimism that are resilience factors [ 142 ], people who enjoy community gardening may have more acceptance and more openness to life change, which in turn could enhance their resilience potentials.

Further work on the associations among openness, resilience, and community gardening will be a valuable contribution to the existing literature, in view of the fact that these associations specific to community gardening have yet to be explored.

1.6. Rationale and Significance of the Present Study

While there has been an increase in popularity in Singapore of community gardening, there is also an increase in published research related to the mental health benefits associated with this activity. However, much of the available research is qualitative and descriptive [ 143 ], which left a gap to be filled through quantitative studies. The preceding sections have highlighted several factors and mechanisms of well-being, stress, and resilience associated, respectively, with contact or connection to nature, and different forms of gardening activities, such as home gardening or community gardening activities. While research literature on the adaptive value of community gardening on well-being and stress is available, there is a scarcity in the research literature highlighting the implications of community gardening on resilience. Besides that, the present understanding of the difference between community gardening and individual or home gardening, as well as the contributions of the contact or connection to nature and social elements of the community gardening, is still poor despite the marked consequences of these two elements on well-being and stress respectively. Given the pivotal role of community gardening in the potential for restoration from stress and other mental health benefits, there is a need to understand these questions with greater depth. Thus, the current study was designed to examine the effects of community gardening through the resilience perspective.

Moreover, as engagement in community gardening has been found to be associated with self-esteem, which is one of the resilience factors, community gardening may have an association with psychological phenomena that are closely linked with self-esteem and resilience, such as optimism. Further work may need to be done to investigate how community gardening individually associates with optimism, in order to further supplement the existing literature. With the significant positive associations between openness to experience and psychological resilience, further work on the associations between openness and community gardening will be a valuable contribution to the existing literature. The present study aims to gain insight into resilience in the context of community gardening, by also examining resilience factors such as self-esteem, optimism, and openness.

Furthermore, there is a deficiency in knowledge about the benefits of the respective elements of community gardening, with much of the existing evidence depending on qualitative data. To date, a query that is still under debate is whether the reported well-being and stress reduction benefits are attributed to the exclusivity of respective individual elements of community gardening such as the provision of the physical activity, connection to nature, gardening experience or social elements, or the combination of all these elements. Several systematic reviews have documented the importance of physical activity or exercise for mental health [ 144 , 145 , 146 ]. However, it is unknown if the presence of physical activity and social elements in community gardening is the core factor that enables community gardening activities to enhance mental health, or if interaction with natural components of the environment is also implicated in positive effects. Thus, research focused on further teasing apart the contributions of these elements of community gardening on the mental health benefits is worth exploring.

Thus, we conducted a cross-sectional type of survey to extend previous studies to examine the implications of community gardening on subjective well-being and stress, as well as to fill in the literature gaps to provide finer clinical understanding and application of community gardening on resilience potentials, along with consideration of the potential contribution of different elements of community gardening.

We will now discuss the aims and hypotheses of the present study.

The aim of the study is to examine the relationship between community gardening and a number of mental health benefits, in the forms of subjective well-being, stress and resilience as well as the respective resilience factors, along with consideration of the potential contribution of physical activity, connection to nature, gardening experience, or social elements, or the combination of all.

Gardening activities typically involve either a social aspect (community gardening) or individual aspect (individual/home gardening), and studies examining differences between groups usually benefit from the inclusion of a control condition. From existing literature, it was predicted that community gardeners, individual/home gardeners and a non-gardening (outdoor activity) control group would differ on the measures of subjective well-being and perceived stress depending on their variations in the gardening experience or social elements. In particular, it was predicted that community gardeners, as compared to individual/home gardeners and non-gardeners (control), would report higher levels of subjective well-being and lower levels of perceived stress, as a result of the combined effects of the elements of physical activity, gardening experiences, contact or connection to nature as well as social interaction. However, there has yet to be consistent and conclusive evidence on the difference in the levels of resilience and resilience factors across community gardening, individual/home gardening, and non-gardening control groups. Therefore, non-directional hypotheses were then adopted. This current knowledge together with indications of existing gaps in understanding led to the formulation of a set of hypotheses as follows.

Community gardeners would report significantly higher levels of subjective well-being than the individual/home gardeners and the non-gardening control group.

Community gardeners would report significantly lower levels of perceived stress than the individual/home gardeners and the non-gardening control group.

Resilience levels would be significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

The levels of the respective resilience factors (i.e., self-esteem, optimism, and openness) would be significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

The levels of self-esteem would be significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

The levels of optimism would be significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

The levels of openness would be significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

Resilience would be positively correlated with subjective well-being.

Resilience would be negatively correlated with perceived stress.

Resilience would be positively correlated with each of the individual resilience factors (i.e., self-esteem, optimism, and openness).

Community gardeners would report significantly higher levels of connection to nature (i.e., the INS score) than the individual/home gardeners and the non-gardening control group.

Connection to nature (i.e., the INS score) would be positively correlated with resilience.

Connection to nature (i.e., the INS score) would be positively correlated with each of the individual resilience factors (i.e., self-esteem, optimism, and openness).

2. Materials and Methods

2.1. participants.

A total of 149 participants accessed the online or paper-based surveys. Of the total access, 31 participants (20.8%) only partially completed the survey. The exclusion criteria for data retention were as follows: (a) participants who did not complete the survey, (b) younger than 18 and older than 100 years of age, or (c) the residents who engaged only in outdoor physical activities alone but not in groups. Thus, a total of 111 participants (68 females, 61.3% and 43 males, 38.7%), aged between 25 and 77 years (M = 53.40, SD = 14.58) completed the study. Amongst the participants, 98 (88.3%) identified themselves as being Chinese, 5 (4.5%) as Malay, 4 (3.6%) as Indian, 2 (1.8%) as Eurasian, and 2 (1.8%) as other ethnicities. The majority had a tertiary education (57.7%), and were primarily full-time employed (41.4%) or retired (24.3%). A summary of demographic details is presented in Table 1 .

Demographic Characteristics (Means (SD), No. (%)) Across Three Groups.

Participants were recruited using the snowball recruitment method from a community dwelling sample residing and engaging in gardening or outdoor activities in Singapore. The gardening group included two groups: community gardeners and individual/home gardeners. Those who engage in non-gardening outdoor activities constitute the control group for the study purposes. These three groups all engaged in activity with some form of physical activity and connection to nature elements but varied in gardening experience or social elements so that the potential contribution of these elements could be compared.

To initiate the recruitment, the study was advertised and distributed to a range of Singapore residents known to be engaged in gardening or outdoor activities. The principal investigator first approached garden leaders involved in the CIB initiative of the NParks in Singapore, and the persons-in-charge from these respective gardening groups: the Community Gardening Groups of the Community Clubs (CC), Residents’ Committees (RC), or Neighbourhood Committees (NC), the Gardening Clubs, and the volunteering gardening groups, as well as the persons-in-charge of outdoor physical activities groups of the CC, RC, or NC. Contact with respective parties was made by email, by phone, or in person. The study and the online survey link were subsequently disseminated internally to the potential participants by the persons-in-charge of the respective parties or the principal investigator. The study and the online survey link were also advertised to individual or home gardeners using posters and study advertisements published on social media platforms (e.g., Facebook) and, thereafter, through snowball recruitment of others who might be interested in the study.

Participants were asked to rate their involvement in different types of activities. Thus, the delineation of three groups was based on the self-reported involvement in different activities, as opposed to assignment of individuals to specified categories into which their activities might not have fit. Nonetheless, best efforts were made to ensure that the participants belonged to only one group, so that a cross-sectional analysis could be conducted. The residents involved in community gardening activities formed the first target group, the community gardening group. The residents who engage in gardening activities, but were individually involved in home balcony or indoor gardening instead of community gardening, formed the second target group, the individual/home gardening group. A comparison group of non-gardeners who participated in outdoor physical activities in groups formed the non-gardening (outdoor activity) control group. Before the commencement of recruitment, ethical approval was obtained from the James Cook University Human Research Ethics Committee for the proposed study (H6730).

2.2. Sample Size

Assuming all hypotheses were supported, an a priori power analysis for a Multivariate Analysis of Covariance (MANCOVA) with six dependent variables was conducted in G*Power to determine a sufficient sample size using an alpha of 0.05, a power of 0.95, and a small effect size ( f 2 = 0.20). Based on the aforementioned assumptions, an optimal sample size was indicated as 72.

2.3. Research Design

A cross-sectional survey research method was selected to address the research questions and was preferred over case study, naturalistic observation, or interview methods because it was more time- and cost-efficient. This cross-sectional study involved the measurement of well-being, stress and resilience levels, as well as resilience factors in community gardeners and participants of other prevalent Singapore outdoor activity pursuits to compare the potential benefits. The study variables included connection to nature, perceived stress, subjective well-being, resilience, self-esteem, optimism, and openness.

2.4. Measures

The survey consisted of questions relating to demographics, participants’ involvement in gardening activities and outdoor activities, participants’ self-rated connection to nature, and the original English version of psychological measures or questionnaires assessing perceived stress, subjective well-being, resilience, self-esteem, optimism, and openness. Singapore is home to a multiethnic and multilingual population with Chinese (74.3%) as the major ethnicity [ 147 ]. As English has become the home language throughout the community, the survey was first created in an English version. However, to accommodate for many others who still use Chinese as their first language, particularly those coming from Chinese backgrounds, a Chinese version of the survey was also created by using the standardized and validated Mandarin or Chinese versions of psychological measures or questionnaires. On the other hand, Malay and Tamil versions of the survey were not created due to the scarce availability of the standardized and validated Malay and Tamil versions.

2.4.1. Demographics

The demographics section of the survey requested information related to participant socio-demographics (i.e., age, gender, ethnicity, education level, occupation status, duration of residency in Singapore).

2.4.2. Involvement in Gardening Activities and Outdoor Physical Activities

A second section requested information regarding the participant’s involvement in gardening activities or a range of other outdoor, non-gardening physical activities, within “the past 12 months” set as the time frame for engagement. Gardening activities were listed as follows: (1) community gardening, (2) gardening at balcony, and (3) growing green plants in indoor spaces (categories 2–3 are considered individual/home gardening for the purposes of the current study). For each activity, participants used the following scale to rate the frequency of the specific gardening activity: 0 = Never, 1 = Less than once per week, 2 = Once per week or 3 = More than once per week.

The outdoor, non-gardening physical activities were listed as follows: Martial Arts (e.g., Tai Chi, Wu Shu, Malay Silat, etc.), Dancing, Brisk walking, Hiking, Jogging, Cycling, Other activities—Alone, and Other activities—In group). These outdoor, non-gardening physical activities were chosen because they are the common physical activities organized by the Community Clubs (CC), Residents’ Committees (RC), and Neighbourhood Committees (NC) that allow regular and group participation, and offer physical intensity. For the latter two items, participants were asked to specify the “other” physical activities that they had engaged in the outdoor environment, but were not listed. For all outdoor physical activity items, participants used the same frequency scale as for gardening activities. Moreover, participants used the following scale to indicate the context of engagement: 0 = Never, 1 = Alone, 2 = In group (with others), or 3 = Both (Alone and In group).

2.4.3. Inclusion of Nature in Self Scale (INS; Schultz, 2001; Schultz, 2002)

The INS is a single-item visual measure assessing the construct, connection to nature. Schultz [ 26 ] advocated that the extent to which a person’s cognitive self-concept includes nature predicts the strength and closeness of the individual’s relationship with nature. To measure participants’ feelings of closeness or connection to nature, participants choose one out of seven choices, each choice with two paired circles representing self and nature, as best representing their “relationship with the natural environment.” Circle pairs range from side-by-side with no overlap (choice 1 being least inclusive) to the final pair that overlap completely and appear as one circle (choice 7 being the most inclusive), with higher scores indicating higher levels of connection to nature.

2.4.4. Brief Resilience Scale (BRS)

The BRS [ 103 , 148 ] is a six-item measure assessing resilience as the ability to bounce back or recover from stress. Participants rate each item (e.g., “I tend to bounce back quickly after hard times”) on a five-point scale ranging from strongly disagree (1) to strongly agree (5). Three items are negatively worded, so they are reverse scored. The BRS is scored by finding the mean of the six items, with higher scores indicating higher resilience. Internal consistency has been found to be high for samples of students and patients, with Cronbach’s alphas ranging from 0.72 to 0.93 [ 103 , 149 ].

2.4.5. Perceived Stress Scale (PSS-10)

The PSS-10 [ 85 , 150 ] is a 10-item measure of perceived stress. The degree to which situations in one’s life are appraised as stressful during the past month (e.g., “In the last month, how often have you felt nervous and ‘stressed’?”) is rated on a five-point scale ranging from never (0) to very often (4). Positively worded items are reverse-scored and the ratings are summed, with higher scores indicating more perceived stress. The PSS-10 has demonstrated adequate reliability and validity, with Cronbach’s alphas ranging from 0.78 to 0.83 [ 150 , 151 , 152 ] and test-retest reliability coefficients ranging from 0.55 to 0.88 [ 152 ].

2.4.6. Personal Wellbeing Index—Adult (PWI-A)

Both the original English and Chinese versions of the PWI-A as well as the user manual can be retrieved from the official website of the International Wellbeing Group [ 153 , 154 ]. As outlined in the manual, the PWI-A is a seven-item measure developed to measure subjective well-being. Respondents rate their satisfaction with seven life domains that are theoretically embedded: standard of living, personal health, achieving in life, personal relationships, personal safety, community-connectedness, and future security. All responses are made on an 11-point scale ranging from no satisfaction at all (0) to completely satisfied (10). The seven domain scores can be summed to yield an average score, with higher scores indicating higher subjective well-being. The PWI-A has demonstrated good internal consistency with Cronbach’s alphas ranging from 0.70 to 0.85, and good test-retest reliability across a 1–2 week interval with an intra-class correlation coefficient of 0.84 [ 155 ].

2.4.7. Rosenberg Self-Esteem Scale (RSE)

The RSE [ 156 , 157 ] is a 10-item measure to assess self-esteem (see Appendix). Respondents rate each item (e.g., “I feel that I have a number of good qualities”) on a four-point scale ranging from strongly disagree (0) to strongly agree (3), with higher scores reflecting greater self-esteem. The RSE has demonstrated reasonable internal consistency reliability with Cronbach’s alpha at 0.77 [ 156 ] and good test-retest reliability for the two-week interval at 0.85 [ 158 ].

2.4.8. Life Orientation Test-Revised (LOT-R)

The Chinese Revised Life Orientation Test was adapted by Lai et al. [ 159 , 160 ] from the original English version of the LOT-R. To measure optimism, the LOT-R is a 10-item measure with six scored items (three positively worded and three negatively worded) and four filler items. Respondents rate each item (e.g., “In uncertain times, I usually expect the best”) from strongly disagree (0) to strongly agree (4). Four filler items will not be scored and the negatively worded items will be reverse-scored. Consequently, only the six scored items (non-filler items) will be summed to derive an optimism score, with higher values implying higher optimism. The LOT-R exhibits reasonable internal consistency with Cronbach’s alpha at 0.78 for the entire six scored items, and test-retest reliability for an undergraduate sample over a four-month interval at 0.68 [ 159 ].

2.4.9. Openness-to-Experience (English and Chinese Versions, International Personality Item Pool (IPIP))

To measure the construct of openness, the 10-item scale of the Openness-to-experience was extracted from the IPIP, which is freely accessible from the IPIP website, http://ipip.ori.org . The website is a public-domain resource that contains over 1000 personality items and over 300 scales constructed from IPIP items. Portions of the item pool have been translated to multiple languages and members of the public can contact the investigators involved with e-mail links listed at the IPIP website [ 161 ]. The Chinese version of the openness-to-experience scale was extracted from the traditional Chinese version of the 50-Item IPIP Representation of the Goldberg’s Markers for the Big-Five Factor Structure [ 162 ]. Within this 10-item measure, each + keyed item (e.g., “Believe in the importance of art”) is scored from very inaccurate (1) to very accurate (5), and each keyed item (e.g., “Avoid philosophical discussions”) is scored from very accurate (1) to very inaccurate (5). The ratings are summed, with higher scores indicating more openness to experience. According to the information at the IPIP website, this 10-item measure exhibits an acceptable level of internal consistency with Cronbach’s alpha at 0.82.

2.5. Procedure

The survey was constructed and hosted using Qualtrics survey software, and was also made available as a printed version for those with limited online access or not comfortable using technology. The printed version of the survey had the same content as the online version, and included both English and Chinese versions.

The study involved voluntary participation. Participants who accessed the survey online were directed to a prefacing page displaying information about the study and the voluntary nature of participation. They were also informed that choosing to proceed to the survey indicated consent and that there was an option to withdraw from the study, with directions to close the browser window. Participants who chose to complete a paper-based survey were provided with a sealable envelope in which to place their completed survey so as to retain the anonymity of their data.

2.6. Statistical Analyses

Data analysis was performed using IBM SPSS Statistics Version 20.0 (IBM Corp., Armonk, NY, USA) with statistical significance p value set to <0.05 for all analyses, without the use of Bonferroni correction as suggested by Perneger [ 163 ]. According to Perneger, Bonferroni adjustments do not assure a “prudent” interpretation of results because these adjustments are concerned with the general null hypothesis, which is irrelevant, and create more issues by increasing the likelihood of type II errors. In the present study, the data analyses were conducted in two steps: demographic analyses and main analyses. The demographic analyses compare the demographic variables across the groups to detect any potential confound. These analyses involve univariate analyses consisting of Pearson’s chi square tests and one-way Analyses of Variance (ANOVAs). The main hypotheses were tested with a one-way Multivariate Analysis of Covariance (MANCOVA) in which gardening activity served as the independent variable (Community gardening, individual/home gardening, non-gardening control), and the levels of perceived stress, subjective well-being, resilience, self-esteem, optimism, and openness served as the dependent variables. Age and connection to nature (INS score) were entered as covariates to ensure that any changes in the DVs were not due to these effects. When MANCOVA was significant, post hoc comparisons were conducted. Lastly, associations between numerical variables were analyzed using Pearson’s product-moment correlation coefficient analysis.

3.1. Preliminary Data Screening

Prior to any analysis, preliminary data screening was conducted to check for missing or erroneous values for the fulfilment of assumptions of normality and multicollinearity. Study data were also assessed for normality distribution via visual scanning of histograms and box-plots. No correlations between dependent variables were r > 0.9, suggesting that multicollinearity was not of concern. The non-significant Box’s M statistics ( p = 0.17) indicated that the assumption of homogeneity of covariance matrices was not violated.

3.2. Reliability of Psychological Measures

Reliability tests were run for all psychological measures used in the present study, and comparative reliabilities for published studies are presented in Table 2 .

Cronbach’s Alphas for the Psychological Measures.

Note: BRS = Brief Resilience Scale, PSS-10 = Perceived Stress Scale, PWI-A = Personal Wellbeing Index, RSE = Rosenberg Self-Esteem scale, LOT-R = Life Orientation Test-Revised.

3.3. Socio-Demographic Characteristics

Socio-demographic characteristics of the three groups are documented in Table 1 . The groups were reasonably demographically homogenous. Across all groups, the majority were Chinese and educated at the tertiary level. Amongst the community gardeners, almost half were female, and the majority were retirees or full-time employed.

Comparison analyses of participant descriptive data across the three groups were conducted. Pearson’s chi square tests showed significant differences in gender, educational level, and occupational status across the three groups, but not ethnicity. These differences were not unexpected due to the adoption of the snowballing recruitment method for participants beyond the community gardeners. An independent-samples t -test was conducted and it showed that there was no significant difference in PWI-A, PSS-10 and BRS scores of males and females overall, with p = 0.795, p = 0.684, and p = 0.302, respectively. Because of the low numbers for some of the educational levels, and occupational status categories in some of the groups, it was not possible to test for the effect of educational level, and occupational status across groups using parametric statistics.

A one-way ANOVA analysis showed that there was a significant difference across the groups on age, F (2, 108) = 17.57, p < 0.001, and INS scores, F (2, 108) = 11.33, p < 0.001. As these differences were statistically significant, these two variables were controlled for in later analyses. Post-hoc comparisons using the Bonferroni test further showed that the individual/home gardening group was significantly younger than the community gardening group ( M = 60.20, SD = 13.27) and the non-gardening control group ( M = 60.20, SD = 13.27), with p < 0.001 and p = 0.001, respectively. However, there was no significant difference in age between the community gardening group and the non-gardening control group, p < 0.397. On the other hand, post-hoc comparisons using the Bonferroni test also showed that the community gardening group reported significantly higher INS scores ( M = 5.44, SD = 1.49) than the individual/home gardening group ( M = 4.394, SD = 1.62), p = 0.009, and the non-gardening control group ( M = 3.71, SD = 1.61), p < 0.001 respectively. However, there was no significant difference in INS scores between the individual/home gardening group and the control group, p = 0.25.

3.4. Effects of Gardening on Psychological Measures

To test Hypotheses 1 to 4 that there are between-group differences on the psychological measures, a one-way MANCOVA was performed in which gardening activity served as the independent variable (community gardening, individual gardening, non-gardening control) and the scores of PSS-10, PWI-A, BRS, RSE, LOT-R, and openness-to-experience scales served as the dependent variables, whilst controlling for age and INS scores. The results of the MANCOVA are presented in Table 3 . Findings showed that there was a statistically significant main effect of gardening on the combined dependent variables, after controlling for age and INS scores, F (12, 202) = 2.48, p = 0.005; Wilk’s Λ = 0.760, partial η 2 = 0.128.

Means (SD) of Study Variables and MANCOVA Results of Differences Across Three Groups While Controlling for Age and Inclusion of Nature in Self (INS) score.

Note. * p < 0.05; ** p < 0.01. Post-hoc analyses indicate that a group differs statistically significantly from b group/s. PWI-A = Personal Wellbeing Index, PSS-10 = Perceived Stress Scale, BRS = Brief Resilience Scale, RSE = Rosenberg Self-Esteem scale, LOT-R = Life Orientation Test-Revised.

Given the significance of the overall test, the results for the dependent variables were considered separately, using an alpha level of 0.05. As the Levene’s test of Equality of Error Variances was not significant for dependent variables except the RSE scores, which measured the level of self-esteem, the data for the RSE scores are viewed with extra caution, by using a lower alpha level p < 0.01 for significance. Univariate analyses showed that gardening had significant effects on the PWI-A scores, F (2, 108) = 5.52, p = 0.005, partial η 2 = 0.094, and BRS scores, F (2, 108) = 4.18, p = 0.018, partial η 2 = 0.073. However, gardening had no significant effect on the PSS-10 scores, F (2, 108) = 0.316, p = 0.73, partial η 2 = 0.006.

With regards to the differences on the resilience factors across the three groups, univariate analyses showed that gardening had significant effects only on the LOT-R scores that measured the level of optimism, F (2, 108) = 4.32, p = 0.016, partial η 2 = 0.075. Gardening had no significant difference on the RSE scores, F (2, 108) = 3.28, p = 0.041, partial η 2 = 0.058, although the community gardening group reported highest RSE scores. Lastly, gardening also had no significant effect on the openness-to-experience scale scores, F (2, 108) = 0.715, p = 0.491, partial η 2 = 0.013.

Post-hoc comparisons using the Bonferroni test showed that the community gardeners reported significantly higher PWI-A scores than the individual/home gardeners, p = 0.010 and the non-gardening control group, p = 0.026, respectively. However, there was no significant difference in the PWI-A scores between the individual/home gardeners and the non-gardening control group, p = 1.00. The community gardeners also reported significantly higher BRS scores than the control group, p = 0.018. While the community gardening group reported higher BRS scores than the individual/home gardening group, this difference was not significant, p = 1.00. Again, the BRS scores of the individual/home gardening group did not differ significantly from that of the control group, p = 0.118. Lastly, the community gardeners reported significantly higher LOT-R scores than the control group, p = 0.012. While the community gardening group reported higher LOT-R scores than the individual/home gardening group, these differences were not significant, p = 0.347. Again, the LOT-R scores of the individual/home gardening group did not differ significantly from the control group, p = 0.531.

3.5. Correlation Analyses

To test the remaining hypotheses, correlation analyses were run to assess whether BRS scores were significantly correlated with PWI-A and PSS-10 scores. In addition, the correlations between BRS scores and the resilience factors, the RSE, LOT-R, and openness-to-experience scale scores were also assessed. Lastly, the correlations between INS scores and BRS, RSE, LOT-R, and openness-to-experience (OTE) scale scores were also assessed. The correlation statistics are reported in Table 4 .

Pearson’s Correlation Statistics for Study Variables.

Notes. n = 111; ** p < 0.01, *** p < 0.001. PWI-A = Personal Wellbeing Index, PSS-10 = Perceived Stress Scale, BRS = Brief Resilience Scale, RSE = Rosenberg Self-Esteem scale, LOT-R = Life Orientation Test-Revised, OTE = Openness to experience, INS = Inclusion of nature in self.

BRS scores were found to be significantly, positively correlated with PWI-A scores, and significantly, negatively correlated with PSS-10 scores. BRS scores were also found to be significantly, positively correlated with RSE scores, LOT-R scores, and openness-to-experience scale scores. These correlations between resilience and the respective resilience factors suggest that the factors are associated constructs but do not measure the same construct, which is consistent with the literature review.

In summary, there are significant differences in age and INS scores (i.e., the measure of connection to nature) across the three groups. Taking these inherent between-group differences into account, gardening was found to have a significant main effect on some of the mental health benefits such as subjective well-being. Specifically, the community gardening group reported highest scores of PWI-A (i.e., the measure of subjective well-being) across the three groups. The community gardening group also reported higher BRS scores (i.e., the measure of resilience) and higher LOT-R scores (i.e., the measure of optimism) than the non-gardening control group. Besides that, the engagement in individual/home gardening activities and in the non-gardening outdoor activities did not appear to have a significant impact on the scores of the psychological measures of subjective well-being, perceived stress, resilience, and resilience factors (i.e., self-esteem, optimism, and openness). Lastly, correlation analyses showed that BRS scores were positively correlated with PWI-A scores and negatively correlated with PSS-10 scores. Moreover, BRS scores were also positively correlated with the resilience factors, the RSE, LOT-R, and openness-to-experience scale scores. INS scores were also positively correlated with BRS, RSE, LOT-R, and openness-to-experience scale scores.

In light of the data of the present study, the following hypotheses were supported:

Community gardeners reported significantly higher levels of subjective well-being than the individual/home gardeners and the non-gardening control group.

Resilience levels were significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

The levels of optimism were significantly different across the community gardeners, the individual/home gardeners, and the non-gardening control group.

Resilience was positively correlated with subjective well-being.

Resilience was negatively correlated with perceived stress.

Resilience was positively correlated with each of the individual resilience factors (i.e., self-esteem, optimism, and openness).

Community gardeners reported significantly higher levels of connection to nature (i.e., the INS score) than the individual/home gardeners and the non-gardening control group.

Connection to nature (i.e., the INS score) was positively correlated with resilience.

Connection to nature (i.e., the INS score) was positively correlated with each of the individual resilience factors (i.e., self-esteem, optimism, and openness).

4. Discussion

We first examine and discuss the key findings reported here in the context of the hypotheses and past research findings. Subsequently, the clinical implications and the limitations of the study, as well as future recommendations are presented.

Through the data gathered from the survey, the present study found evidence in terms of quantitative data for a number of valuable findings. Firstly, consistent with hypothesis 1 (Hypothesis 1), after controlling for the effects of age and connection to nature, the community gardening group reported significantly higher levels of subjective well-being than the individual/home gardening and the non-gardening control groups, with an indication that community gardening activities are superior to individual/home gardening or non-gardening outdoor activities. This superiority is a unique result compared to the past research findings merely documenting the relationship between community gardening and well-being [ 17 , 81 ]. The present study is also different from most of the previous studies in Western countries because it also considered the potential contribution of the individual elements of community gardening on the levels of subjective well-being by comparing to individual/home gardening or non-gardening outdoor activities. It should be noted that the three groups investigated in the present study all engaged in physical activities involving some exposure to nature but varied in gardening experience or social elements. The community gardening group engaged in activities covering physical activity, connection to nature, gardening experience, and social elements compared with the individual/home gardening group in which the social element of gardening was absent, and the non-gardening control group in which the gardening element was absent. As there is no statistically significant difference between the individual/home gardening group and the non-gardening control group, higher levels of subjective well-being reported by the community gardeners likely stemmed from the combined effects of the physical activity, contact or connection to nature, gardening experiences and social elements.

Contrary to Hypothesis 2, there was no significant difference in the levels of perceived stress across the three groups, after controlling for age and the levels of connection to nature. Although the levels of perceived stress tended to be lower for the community gardening group as compared to the other two groups, this difference might only be considered at the level of practical significance if supported in future research of a qualitative nature. These current findings varied from the past studies with qualitative data [ 57 , 81 ], which advocated that taking part in community gardening helped relieve stress. However, the current findings are consistent with a past study with quantitative data [ 91 ], which also found no significant difference in the perceived stress levels between allotment gardeners, home gardeners and those who performed outdoor physical activity. The current findings might be explained by the restorative effects of the contact or connection to nature element, which was also a common element across the groups. Participants across these three groups at least had certain levels of connection to the nature, which would be helpful for the attenuation of deliberate attention through restoration processes that are affected by stress. Further, their activities in nature could also help disrupt the negative stress process [ 13 , 14 , 22 ], resulting in no significant differences in levels of perceived stress across the groups. It could also be argued that the stress reduction effect of community gardening in the present study was non-significant because of the varying baselines of the perceived stress levels of each participant. Thus, the pre- and post-testing design might be considered to more effectively capture the change of stress reduction of engagement in community gardening for each participant. Lastly, despite no significant difference in perceived stress levels across the three groups, the community gardening group still reported the highest levels of subjective well-being, suggesting evidence for the mental health benefits of the community gardening in the Singapore context.

Aligned with Hypothesis 3, resilience levels were significantly different across the groups, after controlling for age and levels of connection to nature. In particular, the community gardening group reported significantly higher resilience levels than the non-gardening control group, but not the individual/home gardening group. Given that the community gardening group engaged in activities covering physical activity, connection to nature, gardening experience and social elements but the individual/home gardening group in which the social element of gardening was absent, and the non-gardening control group in which the gardening element was absent, these findings were expected. It could be argued that the combined effects of the gardening experiences and social elements of the community gardening group could have multiplied and overshadowed the individual effect of the social element of the non-gardening control group. However, the combined effects did not overshadow the individual effect of the gardening experiences element of the individual/home gardening group, suggesting gardening experience played a bigger role than the social element in the proportions of contribution on resilience levels.

Consistent with Hypothesis 5 and Hypothesis 6, correlation analyses show that resilience levels were positively correlated with levels of subjective well-being and negatively correlated with levels of perceived stress, aligning with past research findings [ 108 ]. The overall results shed light onto the positive influence of community gardening on resilience levels, and suggest that there is some association between resilience levels and separate elements like gardening experience or social elements.

Concerning the resilience factors, and consistent with Hypothesis 7, correlation analyses also showed that resilience levels were positively correlated with each of the resilience factors, and levels of self-esteem, optimism and openness. However, contrary to Hypothesis 4.a., no significant difference in levels of self-esteem across the three groups was observed in the study. The current findings thereby differ from those reported by [ 82 ] in which the non-gardeners were recruited from local supermarkets. Wood et al. did not specify whether the non-gardeners in their study engaged in regular physical outdoor activities, so they are potentially different from the non-gardening group of the present study in which the control group engaged in regular, non-gardening, physical outdoor activities. Aligned with Hypothesis 4.b., the levels of optimism were significantly different across the three groups, with significantly higher levels of optimism were observed in the community gardening group than the non-gardening control group. This finding provides a valuable expansion to the existing literature pertaining to optimism [ 133 ] by indicating that community gardening is linked with higher levels of optimism, which in turn potentially enhances the community gardeners’ resilience potentials. Lastly, contrary to Hypothesis 4.c., no significant difference on the levels of openness was observed across three groups in the present study although openness was found to be positively correlated with resilience levels. This finding is unique, in that prior studies have not included openness to experience as a factor of interest, and it therefore helps to expand the literature in terms of resilience and openness, which is one of the resilience factors.

Concerning contact and connection to nature, the present study differs from those in the past (e.g., [ 91 ]) wherein it was assumed that community gardeners had the most engagement with nature during their gardening activity. Instead, the present study measured connection to nature by using the INS scores. Consistent with Hypothesis 8, the community gardening group reported significantly higher levels of connection to nature (i.e., the highest INS score) than the individual/home gardening and the non-gardening control groups. It could be argued that the community gardeners rated themselves as having more connection to nature because they not only have direct contact with the plants they cultivated, but the community garden also provides expanded space and greenery features. This is in comparison to the home gardeners who only have direct contact with the plants they cultivated, and those non-gardeners who engaged in physical activities in outdoor environments who only have contact with green landscapes.

Consistent with Hypothesis 9 and Hypothesis 10, correlation analyses showed that connection to nature was also positively correlated with resilience, whereby similar patterns were observed between levels of connection to nature and each of the resilience factors. This is especially salient for the possible explanation for the benefits of community gardening on resilience levels. In view of the findings, community gardening, particularly in a city-state with spatial constraints such as Singapore, has the potential to help residents to enhance their mental health, through connecting to nature and offsetting the ongoing loss of human-nature interactions [ 164 ].

4.1. Clinical Implications of the Present Study

Based on the key findings of this study, there are several valuable clinical implications. Firstly, the present study validated the contribution of community gardening to subjective well-being, which is a vital aspect of mental health. The findings of the present study, by uniquely comparing across two gardening groups together with a non-gardening control group, further imply that the effect of community gardening is significantly superior to individual/home gardening and non-gardening. This is possibly due to the more powerful, combined effects of the physical activity, connection to nature, gardening experiences, and social elements integrated into community gardening activities.

Secondly, the present study findings presented here fill in the existing literature gap by highlighting the unique implications of community gardening on the participants’ resilience potentials. The present study was the first to offer quantitative data to show that community gardening is linked with higher levels of resilience than with other non-gardening, outdoor social activities. Given the resilience-stress relationship, whereby resilience is frequently discussed as an aspect of adaptive coping and mental health [ 108 ] and is also documented to be trainable [ 165 ], the study’s findings could help to enhance resilience levels of the residents who are at risk for high stress. Specifically, the findings could be used to guide healthcare policies to implement programs designed to enhance resilience and to ameliorate the risk factors to mental health. As stress is common in the current, fast-paced metropolitan society and its negative effects on mental health are indubitable, health care practitioners and community service providers could draw on the growing evidence to introduce community gardening as a useful mental health promotion strategy and encourage people to participate in community gardening activities.

Thirdly, the present study also expands the existing literature by investigating how community gardening is individually associated with resilience factors, self-esteem, optimism, and openness. To further supplement the findings by [ 123 ], the present study distinguished between individual and community gardening as separate aspects. Although no significant difference in self-esteem was found across the groups, the community gardening group was observed to have the highest level of self-esteem. Being the first study that contributed quantitative data assessing optimism levels and resilience amongst community gardeners, the current study findings support the associations between optimism and resilience [ 117 ]. Moreover, the community gardeners recorded higher levels of optimism than the non-gardeners, which further expands the existing literature, extending the mental health benefits of community gardening to optimism and resilience potentials. In addition, being the first study that examined the associations among openness, resilience, and community gardening, these findings make a valuable contribution to the existing literature, albeit if only to confirm that there was no significant differences in openness across the groups. In view of the relationships between community gardening and three resilience factors respectively, the study findings can help guide healthcare professionals to incorporate community gardening into mental health programs or psychological interventions.

Lastly, the present study is unique to the extent that it is the first study to investigate the mental health benefits of community gardening in the Singapore context, which is Eastern-oriented as opposed to the predominance of findings from Western samples. With an ever-increasing spatial constraint, promoting public mental health in cities is a focal challenge. The study findings confirm that the current Singapore community garden movements indeed have potential for sustainable benefits to the mental health of residents in Singapore in terms of subjective well-being and resilience. The improved knowledge on subjective well-being, perceived stress and resilience, as well as the resilience factors, can better guide researchers and clinicians in developing plausible, sustainable strategies to enhance mental health benefits. Besides that, community gardening, which integrates empowerment and social elements, could also be included as part of the therapy in primary care settings or for those with mild emotional distress in Singapore.

4.2. Limitations of the Present Study

Despite the best efforts when designing the present study, there are several limitations that should be highlighted. Firstly, since the present study employed a cross-sectional design, causal inferences between community gardening and the levels of subjective well-being, perceived stress, and resilience should not be implied [ 166 ]. It is possible that individuals who engage in community gardening have more time to commit to this activity (most of the current sample of community gardeners was retirees), which could result in more powerful combined effects on the mental health benefits. Besides that, while participants in all three groups engaged in activities covering physical activity elements, a measure of the duration spent on each activity may be helpful in examining another moderator of this relationship.

Secondly, the sample profile was in a way restricted by the snowballing recruitment method and considered as a representative only of the particular subgroup of people sampled because the sampling coverage is restricted to the contact circles of a particular group of people. This method could have inhibited participation by those individuals who have no access to the internet or technology. Consequently, the sampled population may have a tendency to under-represent those with limited online access or who are not comfortable using technology. To reduce this potential, a printed version was made available, but it was accessible only to those with whom the researcher was able to reach through recruitment advertisements. As there is no single general website for all of the community gardening groups under the CIB initiatives, the principal investigator needed to approach the garden leaders of selected gardening groups, and thereafter snowballing to others who might be interested in the study. Consequently, uneven group sizes might have limited the power of the current study. Besides that, the individual/home gardeners were significantly younger than the other two groups. However, the present study had controlled for age in the analyses. Future studies may consider examining the resilience potentials in closer detail across age ranges.

Lastly, another concern is the extent to the truthfulness of the responses. Survey questionnaires are generally prone to social desirability bias [ 166 ], but the survey method is still relevant and applicable because the present study targeted to assess respondents’ perceptions and judgements (e.g., perceived stress levels), instead of the quantifiable behaviors. To further address this limitation, future studies might consider to gather additional corroborative information by adding clinical interviews. Paulhus [ 167 ] reported that respondents tended to report more desirable responses when they were requested to put identifying information (e.g., name) on the questionnaire than when told not to. Consequently, in order to reduce social desirability bias in the present study, participants were clearly advised that all responses would remain anonymous. Moreover, to reduce response bias, psychological measures with negatively worded items were selected, and their good reliabilities in the present study exclude this as a critical limitation.

Notwithstanding the above limitations, the present study widens the scope of mental health benefits of community gardening by examining resilience potentials. Studying resilience factors across the three groups provides an exclusive contribution to the mental health benefits of community gardening research within an Eastern-oriented context.

4.3. Recommendations for Future Research

It could be prudent to follow up on the current findings with a longitudinal design to track and compare the pre- and post-levels of subjective well-being, perceived stress, and resilience across groups. Moreover, future studies could employ different analyses to examine the mediating or moderating role of the resilience factors on the relationships between community gardening and mental health benefits. Future studies could also look at differentiating adolescent, adult, and elderly individuals who engage in community gardening for direct comparison purposes. Improved knowledge on the benefits of community gardening across these age groups may help policy makers and horticultural therapists decide the direction for the promotion of gardening activity.

5. Conclusions

The present study provides a novel understanding of the mental health benefits of community gardening within the context of Singapore, a high-density urbanized Southeast Asian city-state. The findings suggest that, despite similar levels of perceived stress, the community gardeners demonstrated higher levels of subjective well-being than the individual/home gardening group and the non-gardening control group, indicating the superior effects of community gardening on subjective well-being, a vital aspect of mental health benefits. These novel findings pertaining to community gardening as well as its relationship with resilience levels fill in some of the gaps in the relevant research literature. Moreover, the association between community gardening and optimism levels also provides evidence for the ability of community gardening to enhance resilience potentials, which can help individuals to adapt well to stressful situations. The present study also provides evidence for the notion that community gardening, along with other types of green landscape exposures, can enable residents to connect with nature. This in turn appears to enhance the mental health of community gardeners. Since community gardening is linked with evident mental health benefits, despite the limitations of this study, the additional values of community gardening and its combined effects of physical activity, nature exposure, gardening experiences, and social elements is worth noting. More confirmatory studies or longitudinal studies are needed to examine the feasibility of developing psychological interventions tapping on community gardening.

Acknowledgments

We acknowledge the intellectual contributions of Lidia Suarez and Stanley Loo for their advice on statistical analyses. We also acknowledge the support in the recruitment process provided by Garden Leaders or Persons in Charge of Community Gardening Groups of the Community Clubs (CC), Resident Committees (RC), or Neighbourhood Committees (NC), the Gardening Clubs themselves, and the persons in charge of outdoor physical activity groups of CC, RC, or NC in Singapore. We also take the opportunity to thank our three reviewers for insightful suggestions and comments.

Author Contributions

Conceptualization, W.I.K. and D.D.; Methodology, W.I.K. and D.D.; Validation, W.I.K.; Formal analysis, W.I.K.; Investigation, W.I.K.; Resources, D.D.; Data curation, D.D.; Writing—original draft preparation, W.I.K.; Writing—review and editing, W.I.K. and D.D.; Visualization, W.I.K.; Supervision, D.D.; Project administration, W.I.K. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest.

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Impact of mycoheterotrophy on the growth of Gentiana zollingeri (Gentianaceae), as suggested by size variation, morphology, and 13 C abundance of flowering shoots

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Plant litter: Its dynamics and effects on plant community structure

1991, The Botanical Review

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Plant Ecology

Knut Anders Hovstad

Rafael Villar

Background and aims Plant litter has an important role in terrestrial ecosystems (Lambers et al. 2008). Our aim was to assess the short-term effect of litter from 21 woody species (deciduous and evergreens) on plant growth and root development. Methods We conducted a short-term experiment (10 weeks) under controlled conditions adding litter from 21 woody species to pots with Dactylis glomerata (target species). We determined plant biomass and root development and related these variables to decomposition rate and litter quality. Results Litter from two species enhanced plant growth whereas litter of five species inhibited it. Considering all species in the data set, plant growth was associated to litter with high decomposition rate and high litter quality: high Ca and N concentration and low polyphenols concentration. However, excluding from the analyses the two species that increased growth, litter inhibition effect on plant growth was related to the litterpolyphenols concentration. Plants growing with nutrient-richer litter had a lower proportion of fine roots which could be related to a litter mediated increase in soil nutrient. Conclusions Enhanced plant growth or, on the contrary, plant growth inhibition could be the result of a positive or, in turn, negative balance between nutrient and polyphenols concentration in litter.

Journal of Ecology

Christer Nilsson

Alexandru Milcu

Marcelle Teodoro Lima

This study investigated the hydrological properties of litter in different vegetation cover types, including Eucalyptus sp. plantation, Agroforestry, and Restoration Forest. The research focused on evaluating litter accumulation, composition, water holding capacity, and effective water retention. The results revealed variations in litter accumulation among the stands, and especially Eucalyptus sp., which had a higher proportion of branches compared to leaves. The water holding capacity of the litter differed among the stands. Agroforest and Restoration Forest showed higher litter water capacities than Eucalyptus sp. The composition and decomposition stage of the litter fractions influenced their water retention capabilities, with leaves exhibiting superior water retention. In contrast, branches had lower water absorption due to their hydrophobic nature. Despite these differences, the effective water retention, which indicates the ability of litter to intercept precipitation, was sim...

Soil Biology and Biochemistry

Edward Ayres

Lennard Gillman

The importance of litterfall as an agent of physical damage and mortality to canopy tree seedlings was investigated in two New Zealand forests: Huapai Scientific Reserve, a warm temperate forest and Pureora Forest Park, a cool temperate forest. 200 natural seedlings within the 10-30 cm height class and 200 artificial seedlings, made from plastic straws and wire, were monitored at 4-6 week intervals over two years in each forest. Litterfall was the cause of a significant proportion of seedling mortality in each forest (11-18%). Seedling growth rates were measured and used to estimate the mortality that a cohort of seedlings may suffer due to litterfall in the time taken to grow through the 10-30 cm height class. Up to 38% mortality due to litterfall may occur to such a cohort at Huapai and up to 29% at Pureora. Although mortality due to litterfall of natural seedlings was similar in both forests, damage at Huapai (7%/yr) was almost 3 ¥ greater than at Pureora (2.5%/yr) (P < 0.001). Artificial seedlings were damaged due to litterfall at almost five times the rate at Huapai (16%/yr) than at Pureora (3%/yr) (P < 0.0001). The rate of damage to artificial seedlings at Pureora is similar to that reported for a Northern Hemisphere temperate forest, however, the rate of damage to artificial seedlings at Huapai is much greater, and of a similar rate to those reported from tropical forests. The evolutionary and ecological implications of the differences between the rates of damage at Huapai and at Pureora, and the mechanisms promoting litterfall damage to seedlings, are discussed.

Trends in Ecology and Evolution

Richard Joffre , Dominique Gillon , Adamou Ibrahima

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Collection  18 May 2018

Top 100 in Plant Science

Explore our most highly accessed plant science articles in 2017. Featuring authors from around the World, these papers highlight valuable research within plant science from an international community.

CRISPR/Cas9-induced Targeted Mutagenesis and Gene Replacement to Generate Long-shelf Life Tomato Lines

• Qing-hui Yu
• Patiguli Asmutola

CRISPR/Cas9-mediated mutagenesis of the dihydroflavonol-4-reductase-B (DFR-B) locus in the Japanese morning glory Ipomoea (Pharbitis) nil

• Kenta Watanabe
• Anna Kobayashi
• Michiyuki Ono

An in planta biolistic method for stable wheat transformation

• Haruyasu Hamada
• Qianyan Linghu

Rapid breeding of parthenocarpic tomato plants using CRISPR/Cas9

• Chihiro Abe
• Keishi Osakabe

Rapid generation of a transgene-free powdery mildew resistant tomato by genome deletion

• Vladimir Nekrasov
• Congmao Wang
• Sophien Kamoun

Knockout of OsNramp5 using the CRISPR/Cas9 system produces low Cd-accumulating indica rice without compromising yield

• Bingran Zhao

CRISPR/Cas9-mediated genome editing efficiently creates specific mutations at multiple loci using one sgRNA in Brassica napus

• Jia-Jing Wu

Dissecting the Genetic Basis of Local Adaptation in Soybean

• Nonoy B. Bandillo
• Justin E. Anderson
• Aaron J. Lorenz

The network of plants volatile organic compounds

• Gianna Vivaldo
• Stefano Mancuso

Use of RNAi technology to develop a PRSV-resistant transgenic papaya

• Ruizong Jia

RNAseq analysis reveals pathways and candidate genes associated with salinity tolerance in a spaceflight-induced wheat mutant

• Hongchun Xiong
• Luxiang Liu

Blue-light induced biosynthesis of ROS contributes to the signaling mechanism of Arabidopsis cryptochrome

• Mohamed El-Esawi
• Louis-David Arthaut
• Margaret Ahmad

Intergrative metabolomic and transcriptomic analyses unveil nutrient remobilization events in leaf senescence of tobacco

• Hailiang Zhang
• Yongfeng Guo

Overexpression of annexin gene AnnSp2, enhances drought and salt tolerance through modulation of ABA synthesis and scavenging ROS in tomato

• Javeria Ejaz
• Taotao Wang

Nanopriming technology for enhancing germination and starch metabolism of aged rice seeds using phytosynthesized silver nanoparticles

• Wuttipong Mahakham
• Ajit K. Sarmah
• Piyada Theerakulpisut

Antagonistic interaction between jasmonic acid and cytokinin in xylem development

• Geupil Jang
• Sun Hyun Chang
• Yang Do Choi

Gene expression atlas of fruit ripening and transcriptome assembly from RNA-seq data in octoploid strawberry ( Fragaria  ×  ananassa )

• José F. Sánchez-Sevilla
• José G. Vallarino
• Victoriano Valpuesta

Silencing of OsGRXS17 in rice improves drought stress tolerance by modulating ROS accumulation and stomatal closure

• Sunghun Park

Recurrent water deficit causes epigenetic and hormonal changes in citrus plants

• Diana Matos Neves
• Lucas Aragão da Hora Almeida
• Abelmon da Silva Gesteira

An endophytic microbe from an unusual volcanic swamp corn seeks and inhabits root hair cells to extract rock phosphate

• Hanan R. Shehata
• Christopher Dumigan
• Manish N. Raizada

Exogenous auxin represses soybean seed germination through decreasing the gibberellin/abscisic acid (GA/ABA) ratio

• Haiwei Shuai
• Yongjie Meng

Cu-chitosan nanoparticle boost defense responses and plant growth in maize ( Zea mays L.)

• Ram Chandra Choudhary
• R. V. Kumaraswamy
• Vinod Saharan

Environmental stress is the major cause of transcriptomic and proteomic changes in GM and non-GM plants

• Rita Batista
• Cátia Fonseca
• M. Margarida Oliveira

Fungal endophyte-induced salidroside and tyrosol biosynthesis combined with signal cross-talk and the mechanism of enzyme gene expression in Rhodiola crenulata

• Jin-Long Cui
• Ya-Nan Wang
• Meng-Liang Wang

Metabolic Signatures in Response to Abscisic Acid (ABA) Treatment in Brassica napus Guard Cells Revealed by Metabolomics

• Mengmeng Zhu
• Sarah M. Assmann

A quantitative model of the phytochrome-PIF light signalling initiating chloroplast development

• Carole Dubreuil
• Andreas Grönlund

Integrating transcriptome and microRNA analysis identifies genes and microRNAs for AHO-induced systemic acquired resistance in N. tabacum

• Yongdui Chen
• Jiahong Dong
• Xuewen Wang

Previous crop and rotation history effects on maize seedling health and associated rhizosphere microbiome

• Maria-Soledad Benitez
• Shannon L. Osborne
• R. Michael Lehman

Plant-to-plant communication triggered by systemin primes anti-herbivore resistance in tomato

• Mariangela Coppola
• Pasquale Cascone
• Giandomenico Corrado

Transcriptome Analysis of Mango ( Mangifera indica L.) Fruit Epidermal Peel to Identify Putative Cuticle-Associated Genes

• Julio C. Tafolla-Arellano
• Martín E. Tiznado-Hernández

Salt stress-induced FERROCHELATASE 1 improves resistance to salt stress by limiting sodium accumulation in Arabidopsis thaliana

• Wen Ting Zhao
• Sheng Jun Feng
• Zhi Min Yang

A penalty on photosynthetic growth in fluctuating light

• Percival J. Graham
• Brian Nguyen
• David Sinton

Folivory elicits a strong defense reaction in Catharanthus roseus : metabolomic and transcriptomic analyses reveal distinct local and systemic responses

• Thomas Dugé de Bernonville
• Inês Carqueijeiro
• Vincent Courdavault

DNA barcoding analysis and phylogenetic relationships of tree species in tropical cloud forests

• Zhiyan Deng
• Wenxing Long

Improving “color rendering” of LED lighting for the growth of lettuce

• Vitaliy Vaganov
• Mingjing Tu

The interactive effects of arbuscular mycorrhiza and plant growth-promoting rhizobacteria synergistically enhance host plant defences against pathogens

• Alejandro Pérez-de-Luque
• Stefanie Tille
• Duncan D. Cameron

Functional characterization of the PHT1 family transporters of foxtail millet with development of a novel Agrobacterium -mediated transformation procedure

• S. Antony Ceasar
• Alison Baker
• S. Ignacimuthu

Yucasin DF, a potent and persistent inhibitor of auxin biosynthesis in plants

• Shinichi Tsugafune
• Kiyoshi Mashiguchi
• Ken-ichiro Hayashi

Click chemistry-based tracking reveals putative cell wall-located auxin binding sites in expanding cells

• Jozef Mravec
• Stjepan K. Kračun
• William G. T. Willats

Reductions in root hydraulic conductivity in response to clay soil and treated waste water are related to PIPs down-regulation in Citrus

• Indira Paudel
• Shabtai Cohen

Seed defense biopriming with bacterial cyclodipeptides triggers immunity in cucumber and pepper

• Geun Cheol Song
• Hye Kyung Choi
• Choong-Min Ryu

Ectopic expression of Triticum aestivum SERK genes (TaSERKs) control plant growth and development in Arabidopsis

• Akanksha Singh
• Paramjit Khurana

Efficient increase of ɣ-aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis

• Satoko Nonaka
• Chikako Arai
• Hiroshi Ezura

Facilitation of phosphorus uptake in maize plants by mycorrhizosphere bacteria

• Fabio Battini
• Mette Grønlund
• Iver Jakobsen

Molecular dissection of transcriptional reprogramming of steviol glycosides synthesis in leaf tissue during developmental phase transitions in Stevia rebaudiana Bert

• Gopal Singh
• Gagandeep Singh
• Ram Kumar Sharma

A fossil species of the enigmatic early polypod fern genus Cystodium (Cystodiaceae) in Cretaceous amber from Myanmar

• Ledis Regalado
• Alexander R. Schmidt
• Jochen Heinrichs

Assessment of Genetic Diversity and Population Structure in Iranian Cannabis Germplasm

• Aboozar Soorni
• Reza Fatahi
• Aureliano Bombarely

Mapping QTLs conferring salt tolerance and micronutrient concentrations at seedling stage in wheat

• Babar Hussain
• Stuart James Lucas
• Hikmet Budak

Tomato progeny inherit resistance to the nematode Meloidogyne javanica linked to plant growth induced by the biocontrol fungus Trichoderma atroviride

• Hugo Agripino de Medeiros
• Jerônimo Vieira de Araújo Filho
• Enrique Monte

Antioxidant enzymes in chickpea colonized by Piriformospora indica participate in defense against the pathogen Botrytis cinerea

• Om Prakash Narayan
• Nidhi Verma
• Atul Kumar Johri

Transcriptome and metabolite analyses reveal the complex metabolic genes involved in volatile terpenoid biosynthesis in garden sage ( Salvia officinalis )

• Mohammed Ali

Validation of reference genes for the normalization of the RT-qPCR gene expression of virulence genes of Erwinia amylovora in apple shoots

• Monika Kałużna
• Anita Kuras
• Joanna Puławska

Vapour pressure deficit control in relation to water transport and water productivity in greenhouse tomato production during summer

• Dalong Zhang
• Jianming Li

Insights into grapevine defense response against drought as revealed by biochemical, physiological and RNA-Seq analysis

• Muhammad Salman Haider
• Cheng Zhang
• Jinggui Fang

Arabidopsis RSS1 Mediates Cross-Talk Between Glucose and Light Signaling During Hypocotyl Elongation Growth

• Manjul Singh
• Aditi Gupta
• Ashverya Laxmi

Transcriptome and proteome analysis reveal new insight into proximal and distal responses of wheat to foliar infection by Xanthomonas translucens

• D. Garcia-Seco
• M. Chiapello

Aspergillus flavus infection triggered immune responses and host-pathogen cross-talks in groundnut during in-vitro seed colonization

• Spurthi N Nayak
• Gaurav Agarwal
• Rajeev K Varshney

GBF3 transcription factor imparts drought tolerance in Arabidopsis thaliana

• Venkategowda Ramegowda
• Upinder Singh Gill
• Muthappa Senthil-Kumar

An in vivo biosensing, biomimetic electrochemical transistor with applications in plant science and precision farming

• Nicola Coppedè
• Michela Janni
• Andrea Zappettini

Genome-wide Association Analysis of Powdery Mildew Resistance in U.S. Winter Wheat

• Wenming Zheng

Transcriptomics analysis of salt stress tolerance in the roots of the mangrove Avicennia officinalis

• Pannaga Krishnamurthy
• Bijayalaxmi Mohanty
• Prakash P. Kumar

Identification of miRNA-mediated drought responsive multi-tiered regulatory network in drought tolerant rice, Nagina 22

• Sonia Balyan
• Mukesh Kumar
• Saurabh Raghuvanshi

Morphological, physiological and anatomical traits of plant functional types in temperate grasslands along a large-scale aridity gradient in northeastern China

• Chengyuan Guo
• Renzhong Wang

Transcriptomics reveals multiple resistance mechanisms against cotton leaf curl disease in a naturally immune cotton species, Gossypium arboreum

• Rubab Zahra Naqvi
• Syed Shan-e-Ali Zaidi
• Shahid Mansoor

Field-based high throughput phenotyping rapidly identifies genomic regions controlling yield components in rice

• Paul Tanger
• Stephen Klassen
• John K. McKay

Physiological and transcriptome analysis of heteromorphic leaves and hydrophilic roots in response to soil drying in desert Populus euphratica

• Arshad Iqbal
• Tianxiang Wang
• Huafang Wang

A systems approach to a spatio-temporal understanding of the drought stress response in maize

• Zhenyan Miao
• Zhaoxue Han

A high-efficiency CRISPR/Cas9 system for targeted mutagenesis in Cotton ( Gossypium hirsutum L.)

• Turgay Unver
• Baohong Zhang

A Novel Medium for Enhancing Callus Growth of Hazel ( Corylus avellana L.)

• Mina Salehi
• Ahmad Moieni
• Naser Safaie

Addition of a histone deacetylase inhibitor increases recombinant protein expression in Medicago truncatula cell cultures

• Rita B. Santos
• Ana Sofia Pires
• Rita Abranches

Evolution of rubisco complex small subunit transit peptides from algae to plants

• Md. Abdur Razzak
• Dong Wook Lee
• Inhwan Hwang

Effect of seed position and soil nutrients on seed mass, germination and seedling growth in Peucedanum oreoselinum (Apiaceae)

• Jeremi Kołodziejek

Genome-wide identification of microRNAs responsive to Ectropis oblique feeding in tea plant ( Camellia sinensis L.)

• Anburaj Jeyaraj
• Shengrui Liu
• Chaoling Wei

The emergent rhizosphere: imaging the development of the porous architecture at the root-soil interface

• J. R. Helliwell
• C. J. Sturrock
• S. J. Mooney

Transcriptomic response of durum wheat to nitrogen starvation

• Pasquale L. Curci
• Riccardo Aiese Cigliano
• Gabriella Sonnante

High temperature stress during flowering and grain filling offsets beneficial impact of elevated CO 2 on assimilate partitioning and sink-strength in rice

• Ashish K. Chaturvedi
• Rajeev N. Bahuguna
• S. V. Krishna Jagadish

Genome-wide mapping of DNase I hypersensitive sites reveals chromatin accessibility changes in Arabidopsis euchromatin and heterochromatin regions under extended darkness

• Wenli Zhang

Metabolomics and genomics combine to unravel the pathway for the presence of fragrance in rice

• Venea Dara Daygon
• Mariafe Calingacion
• Melissa A. Fitzgerald

The Arabidopsis miR396 mediates pathogen-associated molecular pattern-triggered immune responses against fungal pathogens

• Mauricio Soto-Suárez
• Patricia Baldrich
• Blanca San Segundo

A time series transcriptome analysis of cassava ( Manihot esculenta Crantz) varieties challenged with Ugandan cassava brown streak virus

• D. K. Berger
• M. E. Ferguson

The plant cell-wall enzyme AtXTH3 catalyses covalent cross-linking between cellulose and cello-oligosaccharide

• Naoki Shinohara
• Naoki Sunagawa
• Kazuhiko Nishitani

Stimulation in primary and secondary metabolism by elevated carbon dioxide alters green tea quality in Camellia sinensis L

• Wen-Yan Han

Breeding and study of two new photoperiod- and thermo-sensitive genic male sterile lines of polyploid rice ( Oryza sativa L.)

• Xianhua Zhang

Harvesting more grain zinc of wheat for human health

• Xin-Ping Chen
• Yue-Qiang Zhang
• Chun-Qin Zou

Transcriptome profiling of genes involved in induced systemic salt tolerance conferred by Bacillus amyloliquefaciens FZB42 in Arabidopsis thaliana

• Shaofang Liu
• Haiting Hao

Comparative RNA-seq analysis of transcriptome dynamics during petal development in Rosa chinensis

• Qixiang Zhang

Dynamic transcriptome and phytohormone profiling along the time of light exposure in the mesocotyl of rice seedling

• Fangjun Feng

Transcript profiling of two potato cultivars during glycoalkaloid-inducing treatments shows differential expression of genes in sterol and glycoalkaloid metabolism

• Nurun Nahar
• Erik Westerberg
• Folke Sitbon

GWAS, QTL mapping and gene expression analyses in Brassica napus reveal genetic control of branching morphogenesis

Global profiling of phytohormone dynamics during combined drought and pathogen stress in Arabidopsis thaliana reveals ABA and JA as major regulators

• Aarti Gupta
• Hiroshi Hisano

Phylogeny, historical biogeography and characters evolution of the drought resistant fern Pyrrosia Mirbel (Polypodiaceae) inferred from plastid and nuclear markers

• Xueping Wei
• Bengang Zhang

The molecular dialogue between Arabidopsis thaliana and the necrotrophic fungus Botrytis cinerea leads to major changes in host carbon metabolism

• Florian Veillet
• Cécile Gaillard
• Sylvain La Camera

The NAC-type transcription factor OsNAC2 regulates ABA-dependent genes and abiotic stress tolerance in rice

• Jiabin Shen

DES-TOMATO: A Knowledge Exploration System Focused On Tomato Species

• Sónia Negrão
• Vladimir B. Bajic

Impact of salt stress, cell death, and autophagy on peroxisomes: quantitative and morphological analyses using small fluorescent probe N-BODIPY

• Deirdre Fahy
• Marwa N. M. E. Sanad
• Andrei Smertenko

Rewiring carotenoid biosynthesis in plants using a viral vector

• Eszter Majer
• Briardo Llorente
• José-Antonio Daròs

A mobile pathogenicity chromosome in Fusarium oxysporum for infection of multiple cucurbit species

• Peter van Dam
• Like Fokkens
• Martijn Rep

Genome-wide association study Identified multiple Genetic Loci on Chilling Resistance During Germination in Maize

• Guanghui Hu
• Zhiwu Zhang

Induction of auxin biosynthesis and WOX5 repression mediate changes in root development in Arabidopsis exposed to chitosan

• Federico Lopez-Moya
• Nuria Escudero
• Luis V. Lopez-Llorca

Population genomic insights into variation and evolution of Xanthomonas oryzae pv. oryzae

• Samriti Midha
• Kanika Bansal
• Prabhu B. Patil

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