暖湿化气候情景下喀斯特木本植物群落构建机制

Community assembly mechanisms of karst woody plants under climate warming and humidification

云南喀斯特区域是滇桂黔岩溶石漠化重点治理区之一,探讨气候暖湿化下植物群落演替阶段的构建特征是生态恢复和森林管理可持续的关键。以气候暖湿化为背景,将喀斯特天坑作为天然“开顶式气室”,天坑南坡地下森林为群落演替顶极。联合系统发育和功能性状探讨演替序列(坑外针阔混交林,坑外常绿阔叶林,坑内常绿阔叶林)的群落构建机制。结果发现:(1)演替前期植物性状的系统发育信号较弱,叶长宽比、叶面积、叶厚度和比叶面积的系统发育信号显著,但功能性状的保守性较弱;演替后期植物性状转为趋同进化,系统发育信号均不显著。(2)演替阶段植物群落的系统发育多样性逐渐降低,并与物种丰富度显著正相关。(3)系统发育指数NRI(净亲缘指数)和NTI(最近种间亲缘指数)由小于0转为大于0,功能性状结构指数TraitSESMPD(标准化平均配对性状距离指数)和TraitSESMNTD(标准化平均最近相邻性状距离指数)均大于0。演替阶段的群落构建过程由生境过滤和物种间相互作用所主导。(4)系统发育和功能性状结构指数主要与土壤含水量、全磷和速效钾含量显著负相关。演替阶段下土壤水分和养分受限时群落趋于聚集,群落构建过程支持生态位假说。研究可为喀斯特植物群落构建机制提供新思路,可为群落结构优化提供科学参考。

Karst landforms in Yunnan is one of the priorities of karst desertification management in Yunnan-GuangxiGuizhou provinces.Exploring the community assembly characteristics of succession stages under climate warming and humidification is essential for ecological restoration and sustainable forest management.In the context of climate warming and humidification,karst tiankeng was taken as the natural“open top chamber”and the underground forest on tiankeng's south slope as the community succession apex.The community assembly mechanism in successional sequences(mixed coniferous forest outside the tiankeng,evergreen broadleaf forest outside the tiankeng,and evergreen broadleaf forest inside the tiankeng)is explored,which is based on phylogenetic and functional traits.The results showed that:(1)the phylogenetic signals of plant traits were lower in the early succession stage,with significant phylogenetic signals for leaf aspect ratio,leaf area,leaf thickness,and specific leaf area,while functional traits were less conserved.In the late succession stages,the plant traits evolved convergently and none of the phylogenetic signals were significant.(2)The phylogenetic diversity of plant communities gradually decreased during the succession stage,and was significantly and positively correlated with species richness.(3)The phylogenetic indices for NRI(Net Relatedness Index)and NTI(Nearest Taxon Index)shifted from less than 0 to greater than 0,and the functional trait structure indices for TraitSESMPD(Standard Effect Size of Mean Pairwise Trait Distance)and TraitSESMNTD(Standard Effect Size of Mean Nearest Trait Distance)were both greater than 0.Community assembly processes in successional stages were driven by environmental filtering and interspecific interaction.(4)Phylogenetic and functional trait structure indices were negatively correlated with soil water content,total phosphorus,and available potassium.Under the successional stage,the community tended to assemble when soil water and nutrients were limited,and the community assembly process supported the ecological niche hypothesis.Our findings will contribute new perspectives to the community assembly mechanism of karst plant and provide scientific reference for community structure optimization.