物种多样性和功能性状驱动高寒草原地上生物量对长期禁牧的响应

Diversity of species and functional traits drive jointly responses of aboveground biomass to long-term grazing exclusion at alpine steppe

围封对草地生物多样性和初级生产力的影响是草地生态学研究的热点问题之一。基于2013—2021年在青藏高原东北部紫花针茅(Stipa purpurea)高寒草原围栏内外植物群落长期调查数据,从物种多样性、功能性状的角度解析了高寒草原地上生物量对长期围封的生态响应过程。结果表明:(1)围封处理对高寒草原物种多样性的负效应具有强烈的时间依赖性。围封处理显著提高地上生物量,但也显著降低了生物量稳定性和异步性,意味着高寒草原稳定的、可持续的生态系统服务功能被长期围封处理削弱。(2)植物功能性状对长期围封处理表现出差异性响应模式;与叶绿素性状相比,叶形态性状对长期围封处理表现出更强的敏感性。(3)物种多样性和功能性状与地上生物量之间均存在显著相关关系,并且物种多样性的影响被功能性状调控进而对地上生物量发挥间接效应,群落加权性状和功能分异度共同对草地生物量发挥直接的主导效应。研究结果证明了植物功能性状通过介导物种多样性与其共同驱动高寒草原地上生物量对长期围封的响应。因此,在未来草地管理过程中,同步研究植物物种和功能属性对于全面揭示生态系统的响应机制至关重要。

Responses of biodiversity and productivity at grassland to fencing have been a hotspot in grassland ecology for a long period.In this study,long-term field investigation along inside and outside of the fence at Stipa purpurea alpine steppe in northeastern of the Qinghai-Tibetan Plateau from 2013 to 2021 was used to elucidate ecological responses processes of aboveground biomass of alpine steppe to long-term fencing from perspectives of species diversity and plant functional traits.The main results showed as follows:(1)the negative effects of fencing treatment on species diversity presented strong time-dependence,and the aboveground biomass increased but both stability and asynchrony of biomass decreased after experiencing long-term fencing,suggesting that potential of stable and sustainable provision of eco-services were eroded by the fencing treatment;(2)Responses of plant functional traits to long period fencing were different.Specifically,the sensitivity to the fencing was stronger in morphological trait than that in chlorophyll traits;(3)The significant relationships between the biomass and species,functional traits diversity were also detected,and effects of species diversity regulated by functional traits played indirect roles to aboveground biomass,specially community-weighted traits and functional divergence index jointly played directly dominant effects on biomass.The study demonstrates that plant functional traits through mediating species diversity drive jointly responses of aboveground biomass to long-term grazing exclusion at alpine steppe.Therefore,evaluating the plant species and functional trait factors simultaneously would be all-important for revealing comprehensively ecosystem responses to environmental perturbations at grassland managements in the future.