青藏高原北部戈壁植物群落物种、功能与系统发育β多样性分布格局及其影响因素

The drivers of plant taxonomic,functional,and phylogeneticβ-diversity in the gobi desert of northern Qinghai-Tibet Plateau

戈壁荒漠广泛分布于全球干旱和极旱区域,是我国陆地生态系统的重要组成部分。由于自然环境恶劣和交通条件限制,目前有关戈壁植物群落物种、功能和系统发育等多维度β多样性形成机制的系统研究还很缺乏,严重制约着对戈壁植物多样性维持机制的认知。本文以青藏高原北部61个典型戈壁生境植物群落为研究对象,通过构建系统发育树和测量8个关键功能性状,获取戈壁生境的物种、功能和系统发育β多样性,比较3个维度β多样性格局与零模型的差异,同时量化环境距离和地理距离对其的相对影响,以探讨戈壁植物多样性的形成机制。结果显示:(1)戈壁植物的物种、功能和系统发育β多样性均表现出显著的距离衰减效应;(2)戈壁植物的物种、功能和系统发育β多样性均表现为非随机的格局;(3)由于功能性状趋同进化,植物功能和系统发育β多样性变化趋势并不一致;(4)环境差异对植物3个维度β多样性均有着比空间距离更为重要的影响,且土壤含水量、地表砾石盖度等局域生境因素的影响比气候更为强烈。以上结果表明,戈壁植物的β多样性可能主要由局域生境过滤作用控制,且不同维度的β多样性分布格局并不一致。

Aims:Uncovering the assembly mechanism that shapes the large-scale biodiversity patterns is a key challenge in ecology.Numerous previous studies have demonstrated that multiple ecological processes can simultaneously regulate plant community assembly.However,how they shape the plant taxonomic,functional,and phylogeneticβ-diversity of gobi deserts remains unclear,hindering the understanding of gobi plant assembly processes and diversity maintenance.Methods:We selected 61 sites from major gobi desert habitat types across northern Qinghai-Tibet Plateau.Plant species abundance,molecular phylogeny,as well as eight functional traits including:leaf nitrogen concentrations(LNC),leaf phosphorus concentrations(LPC),leaf area(LA),specific leaf area(SLA),fine root nitrogen concentrations(RNC),fine root phosphorus concentrations(RPC),root length(RL),specific root length(SRL),and associated environmental variables were measured.We then tested the relative effects of different assembly processes on taxonomic,functional and phylogenetic diversity using null model and variation partitioning analyses.Results:Plant taxonomic,functional,and phylogeneticβ-diversity all significantly increased with geographic distance,whereas taxonomic and functionalβ-diversity were more strongly related to geographic distance.Null model analysis revealed that three facets of plantβ-diversity exhibited a non-random pattern,indicating niche processes may dominate the gobi desert plant community assembly.Plant functionalβ-diversity exhibited clustering patterns,while phylogeneticβ-diversity displayed dispersion patterns.Among eight traits,only LA and RL demonstrated significant but weak phylogenetic signals,suggesting gobi plant functional traits were not conserved throughout evolution.Variation partitioning analysis further indicated that compared with geographic distance,environmental distance could better explain the variation in all three facets of plantβ-diversity.More importantly,local habitat factors,such as soil moisture content and gravel coverage,drove the variation in both three facets of plantβ-diversity rather than climatic factors.Conclusions:These results demonstrated that niche processes,such as habitat filtering,may determine the different facets of plantβ-diversity in the gobi desert,and the distribution patterns of plant functional and phylogeneticβ-diversity were significantly different.In addition,the mismatch between functional and phylogeneticβ-diversity patterns may be partly caused by functional traits that were not conserved along the phylogeny.Taken together,our findings provide new understanding for plant assembly mechanism in extremely harsh environment regime.