Functional diversity and redundancy of subalpine meadows subjected to anthropogenic disturbances

人为干扰下的亚高山草甸功能多样性和功能冗余

Aims The aims of this study were to assess how functional diversity(FD)and functional redundancy respond to subalpine meadow ecosystem degradation under anthropogenic disturbance and how species contribute to functional redundancy along the disturbance gradient.Methods The study was carried out in the subalpine meadow in Mount Jade Dragon,which is located at the southeastern edge of the Tibetan Plateau.Four disturbance intensities[no disturbance(ND),weak disturbance(WD),moderate disturbance(MD)and severe disturbance(SD)]were identified.Species richness,soil properties and five key plant functional traits were assessed along the disturbance gradient.Simpson’s diversity index,FD based on the Rao algorithm,functional redundancy,community-weighted mean of each functional trait and species-level functional redundancy were determined.Important Findings Unimodal change pattern of FD and functional redundancy along the disturbance gradient were found in the present study,with their maximum in MD and WD,respectively.Species diversity showed a decreasing trend with increasing disturbance intensity.As disturbance intensified,species with traits related to conservative growth strategies,such as low specific leaf area(SLA)and high leaf dry matter content(LDMC),decreased,whereas species with resource acquisitive strategies,such as small plant,high SLA and low LDMC,increased in the community.At the species level,species showed species-specific roles in functional redundancy.Notably,some species were important in the community in terms of their unique function.For instance,Ligularia dictyoneura in ND and Potentilla delavayi in MD and SD.

人为干扰程度的加剧会引起植物群落物种多样性和功能多样性的改变,并降低生态系统的稳定性。较高水平的功能冗余对于物种损失引起的生态系统功能和稳定性的改变起到了重要的缓冲作用。然而,关于亚高山草甸植物群落功能冗余对干扰的响应的研究相对较少。本研究的目的是,确定人为干扰下不同退化程度的亚高山草甸,其植物群落功能多样性和功能冗余对干扰的响应特征,及不同物种对功能冗余的贡献程度及其在干扰梯度上的变化规律。研究区位于青藏高原东南缘玉龙雪山上的亚高山草甸。本研究识别出4类干扰强度(无干扰、弱干扰、中度干扰和重度干扰),测定了干扰梯度上的植物物种组成、土壤性质和5个关键的植物功能性状等指标,进一步计算了Simpson多样性指数、功能多样性指数(RaoQ)、功能冗余度、群落的植物功能性状加权平均值(CWM)以及物种水平的功能冗余等指数。研究结果表明,功能多样性和功能冗余在干扰梯度上呈现单峰变化规律,即二者分别在中度干扰、弱干扰下达到最大值。物种多样性在干扰梯度上整体呈下降趋势。随着干扰程度的增加,采取保守生长策略并具有相关性状特征(如较低比叶面积和较高的干物质含量)的物种的丰富度降低,采取资源获取策略并具有相关性状(如低矮植株、较高的比叶面积和较低的干物质含量)的物种增加。不同物种的功能冗余程度存在差异。值得注意的是,一些物种在群落中扮演着独特的功能角色,如无干扰梯度下的网脉橐吾(Ligularia dictyoneura)以及中度和重度干扰梯度下的滇西委陵菜(Potentilla delavayi)。