Understanding Community Assembly Based on Functional Traits, Ontogenetic Stages, Habitat Types and Spatial Scales in a Subtropical Forest

Abstract

Community assembly in natural communities is commonly explained by stochastic and niche-based processes such as environmental filtering and biotic interactions. Many studies have inferred the importance of these processes using a trait-based approach, however, there are still unknowns around what factors affect the importance of different assembly processes in natural communities. In this study, the trait dispersion patterns of 134 species were examined across different functional traits, habitat types, ontogenetic stages and spatial scales from a 20-ha Dinghushan Forest Dynamic Plot in China. The results showed that (1) functional traits related to productivity such as specific leaf area and leaf area mainly showed functional clustering, indicating these two functional traits were more affected by environmental filtering. However, trait dispersion patterns depended on more than the ecological significances of functional traits. For example, trait dispersions of leaf dry matter content, leaf thickness and maximum height did not show consistent patterns across habitat types and ontogenetic stages, suggesting more complex mechanisms may operate on these traits; (2) the trait dispersion varied with the habitat types and ontogenetic stages. Specifically, we found that habitat types only affected the strength of trait dispersions for all the five traits, but ontogenetic stages influenced both the strength and direction of trait dispersions, which depended on the traits selected; (3) the relative importance of soil, topography and space to trait dispersion varied with ontogenetic stages. Topography and space were more important for trait dispersion of saplings but soil was more important for trait dispersion of adults; (4) biotic interactions dominated community assembly at smaller spatial scales but environmental filtering dominated community assembly at larger spatial scales. Overall, the results highlight the importance of functional traits, habitat types, ontogenetic stages and spatial scales to community assembly in natural communities.

Relationship between Rural Settlements’ Plant Communities and Environmental Factors in Hilly Area of Southeast China

“…Altitudes and slope aspects have a significant impact on the growth of trees [27,28], and topographic factors affect the growth and diversity of plants according to different soil properties [29]. Moreover, soil type, topography and spatial scale have a significant impact on the collective distribution of subtropical forest communities [30]. Furthermore, the vegetation in mountain areas is affected by several environmental factors, such as slope aspect, slope, and altitude, and the relationship curve between plant community diversity and altitude in different slope aspect was significantly different [31].…”

Effects of soil resource availability on patterns of plant functional traits across spatial scales

“…It is noteworthy that different studies often calculate standing biomass as proxies of environmental gradients (Costa et al, 2017 ; Lhotsky et al, 2016 ; Liu et al, 2010 ) and this method implicitly assumes that the environmental stress increases with decreasing standing biomass (Grime, 1977 ; Gross et al, 2010 ). However, the variation in standing biomass could be driven by the topography, soil, or microhabitat properties in the research area (Gross et al, 2010 ; Michalet, 2006 ), which makes the comparison between different studies without basis and leads to conflicting empirical supports (Li et al, 2019 ). Secondly, whether the SDH is true for different functional traits is still unknown, because different functional traits may respond differently to environmental gradients (Li et al, 2019 ; Wang et al, 2018 ).…”

“…However, the variation in standing biomass could be driven by the topography, soil, or microhabitat properties in the research area (Gross et al, 2010 ; Michalet, 2006 ), which makes the comparison between different studies without basis and leads to conflicting empirical supports (Li et al, 2019 ). Secondly, whether the SDH is true for different functional traits is still unknown, because different functional traits may respond differently to environmental gradients (Li et al, 2019 ; Wang et al, 2018 ).…”

“…It is undeniable that trait dispersion may depend on which functional traits are involved (Li et al, 2019 ; Wang et al, 2018 ). As different functional traits are often related to different ecological strategies (Violle et al, 2007 ), testing our hypotheses based on single and multivariate trait dispersions may provide more insights about particular niche axes (Lhotsky et al, 2016 ; Spasojevic & Suding, 2012 ).…”

“…Moreover, the detectability of trait dispersion is also scale‐dependent (Cavender‐Bares et al, 2009 ; Weiher & Keddy, 1995 ; Zhang et al, 2018 ). For example, trait overdispersion has been more often detected at small spatial scales where competitive adversity predominates (Li et al, 2019 ; Price et al, 2017 ). Additionally, previous studies also found that the relative importance of environmental variables to community assembly increased with increasing spatial scales (Chase, 2014 ; Legendre et al, 2009 ).…”