Divergent Abiotic Stressors Drive Grassland Community Assembly of Tibet and Mongolia Plateau

Abstract

Multiple ecological processes simultaneously govern community assembly, but it remains unclear how abiotic stressors regulate the relative importance of these processes among different biogeographic regions. Therefore, we conducted a comprehensive study on the responses of community assembly to varying environmental gradients, using the mean, variance, skewness, and kurtosis of plant height (height), specific leaf area (SLA) and leaf dry matter content (LDMC) distributions on the Tibetan Plateau (TP) and the Mongolian Plateau (MP). Our results showed that the prevalence of trait convergence across all grasslands in both TP and MP seem to be the result of abiotic filtering or weaker competitive exclusion etc. These trait-convergence assembly processes decrease the functional dispersion but increase the evenness of the trait frequency distribution. The mean, variance, skewness, and kurtosis responses of grassland communities to abiotic stress varied between the TP and MP. On average, plant trait distribution was mainly driven by temperature on the TP, and low-temperature stress altered the community assembly rules. In contrast, water availability shaped plant trait frequency distributions on the MP, and drought stress mediated the balance between different assembly processes. Our results provide empirical evidence that divergent abiotic stressors regulate the grassland community assembly on the TP and MP. Together, our study speculates that different aspects of future climate change, such as climate warming and changing precipitation patterns, on community assembly are dependent on regional climatic regimes.

Testing the Functional and Phylogenetic Assembly of Plant Communities in Gobi Deserts of Northern Qinghai–Tibet Plateau

“…Stress-dominance hypothesis believes that abiotic filtering would dominate community assembly and leads to functional phylogenetic convergence in a more stressful habitat, while biotic interaction, such as competition exclusion, plays a major role and resulting in divergence in a more favorable environment (Schöb et al, 2013 ; Coyle et al, 2014 ). In this study, we observed that most traits, as well as all the traits combined exhibited functional convergence, consistent with the findings of Chinese grasslands (Wang et al, 2021a ). This may suggest that abiotic filtering drives the Gobi plant community's functional structure.…”

“…However, plant functional and phylogenetic distributions were driven by a wide range of environmental factor (López-Angulo et al, 2018 ; Backhaus et al, 2021 ; Catano et al, 2021 ). For example, trait convergence was mainly driven by temperature on the Tibet Plateau, whereas water availability governs trait convergence on Mongolian Plateau (Wang et al, 2021a ). This study found that the distribution patterns of phylogeny and most traits were mainly influenced by local habitat factors, such as gravel coverage and soil condition, rather than climate.…”

“…More importantly, variations in environmental factors can alter the balance between different assembly processes (Lhotsky et al, 2016 ; Ding et al, 2019 ; Wang et al, 2021a ). Depending on ecosystem types and inquiry scales, the plant community assembly is influenced by various environmental factors such as elevation, temperature, and soil attributes (Bernard-Verdier et al, 2012 ; Luo et al, 2019 ; Wang et al, 2021a ).…”

“…More importantly, variations in environmental factors can alter the balance between different assembly processes (Lhotsky et al, 2016 ; Ding et al, 2019 ; Wang et al, 2021a ). Depending on ecosystem types and inquiry scales, the plant community assembly is influenced by various environmental factors such as elevation, temperature, and soil attributes (Bernard-Verdier et al, 2012 ; Luo et al, 2019 ; Wang et al, 2021a ). Therefore, exploring the influence of environmental factors on plant phylogenetic and functional trait distribution may provide new insights for predicting how plant community assembly responds to future climate changes (Enquist et al, 2015 ; De Pauw et al, 2021 ).…”

“…Therefore, testing the relative roles of the different processes in shaping plant functional and phylogenetic structure in the Gobi deserts of TP may provide new insights into the mechanisms underlying the generation and maintenance of plant diversity under global change. Indeed, the plant community assembly and its determinants have been well examined in steppe and meadow ecosystems of TP (Wang et al, 2021a , b ). However, few studies to date have focused on elucidating the assembly processes that determine plant functional and phylogenetic structures across the Gobi deserts of TP.…”