Multi-scale Community Assembly Mechanism Based On Intraspecific Trait Variation In Shrub Communities In Arid Areas

Mechanism of community assembly has long been a core issue in ecology,and the important process of species coexistence and the maintenance of biodiversity.The method based on functional traits has been widely used in the study of plant community construction assembly.Previous studies on community assembly are mainly focused on trait differences among species,but intraspecific trait variation also plays an important role in community assembly.Different forces are known to shape the patterns of distribution and the abundance of organisms at different spatial scales.In general,at small spatial scales,coexistent species would show trait divergence or the frequency of random trait patterns.In stark contrast,at large spatial scales,coexistent species would show trait convergence.Previous studies on arid or semi-arid plant communities mainly focused on trait differences among species,but our study focused on intraspecific trait variation.Notably,trait-based diversity patterns and community assembly mechanisms are heavily associated with spatial scale.Therefore,our study mainly focused on community assembly patterns based on intraspecific trait variation at different spatial scales.Deserts are one of the most impacted ecosystems currently facing selection pressures due to changes in climate and land use.It is necessary to understand the biodiversity and community assembly patterns of desert systems.Our study system is located at the edge of the Tengger Desert in China.In this study,we established a 50×50 m~2 plot with different small quadrats(5×5 m~2?10×10 m~2?15×15 m~2?20×20 m~2?25×25 m~2),the dominant shrub species is Reaumuria soongorica.All species within each 5×5 m~2 sub-plot were identified,and the abundance,coverage.Fourteen traits(LCC,LDMC,LPC,LNC,SDMC,SCC,SNC,RCC,RNC,RDMC,CR,LL,SLA,H)were chosen to calculate the functional distances of single traits and multiple traits.Species diversity and functional diversity at different spatial scales were then calculated.A null model approach was used to test the trait-based assembly processes of the ecosystem studied.In this study,we compared the community assembly patterns of based on trait differences among species and intraspecific trait variation at different spatial scales.The results show that:(1)Functional and species diversity showed inconsistent patterns at different spatial scales(in?and?levels),Species diversity increased with the increase of spatial scale.Species?diversity showed a downward trend with the increase of spatial scale,while functional?diversity and?diversity showed no significantly changes in spatial scale gradient.(2)It was found that ITV had a large impact on functional diversity and that this effect was related to different types of traits(chemical traits or morphological traits).Considering the intraspecific trait variation(ITV),chemical traits tend to exhibit higher functional?diversity and?diversity,but the morphological traits showed lower functional?diversity and?diversity;f functional?diversity and?diversity have the same variation trend along spatial scale.(3)Different,even opposite,functional structures were found at increasing scales in singletrait analyses without ITV,but these structures showed similar convergence in multipletrait analyses.Without ITV,the functional structure of multiple traits showed filtering patterns at different spatial scales,while different single traits may exhibit random,convergent or divergent functional structures.(4)Considering ITV,plant communities showed stochastic distribution patterns based on either single traits or multiple traits,indicating that intraspecific trait variation(ITV)may play an important role in community assemby and the community assemby process may be a neutral process at a certain leve,but further research is needed.In conclusion,our study shows the importance of intraspecific trait variation in the analysis based on functional traits in multi-scale in the extreme environments.When considering ITV,the deterministic processes in community assembly may be diluted in our research,indicating that intraspecific trait variation is important for studying assembly mechanisms in species-poor communities.