长期不同载畜率放牧条件下荒漠草原物种多样性及生产力动态的变化机制

The grassland species diversity maintained the sustainability and the productivity of the grassland ecosystem. The changes of species composition and interspecies relationship which introduced by grazing are most important factors on the species diversity. Species diversity is one of key factors on the ecosystem stability, productivity and nutrients dynamics. It is a basis that unerstand the relationship between stocking rate and the species composition on the rangeland management. The relationship between The productivity dynamic study in different stocking rate can provide the basic data for the degraded grassland recovery. Based on the long term stocking rate experiment in a stipa breviflora Desert Steppe, This study will reveal the maintenance and the process mechanism of the effect of different sheep stocking rate on the plant species composition and ecosystem productivity dynamics, especially focus on the maintenance and the response mechanism of plant species composition and productivity dynamics in the different intake process, stocking rate condition and different influence by abiotic factors, such as soil nurtrients, long term precipitation and temperature change. Our study also will understand the effect of long term grazing on the species composition changes in the derser steppe, analyse the intrinsic linkage of species diversity and ecosystem productivity in the different level (species, functional group and community), also reveal the relationship between species diversity and ecosystem function under the different stocking rate. The results will provide the therical basis to the sustainable development of the grassland ecosystem and the conservation of biodiversity.

草地植物组成的多样性维持着草地生态系统的可持续性和生产力。放牧导致植物群落物种组成和种间关系的变化是物种多样性变化的主要根源；生物多样性是控制生态系统稳定性、生产力和养分动态的重要因素。理解载畜率和物种组成的关系是草地可持续管理的基本要素，不同载畜率放牧条件下草原生态系统生产力动态研究，可为退化草原生产力恢复提供科学依据。本项目以短花针茅荒漠草原为对象进行不同载畜率的长期对比试验，探讨荒漠草原植物群落物种组成和草地生产力在不同绵羊载畜率下的维持与响应机制，尤其是在家畜采食过程、载畜率等生物因素和土壤养分状况、长期水热条件变化等非生物因素控制下的维持与响应机制，了解长期放牧对草地种类组成的影响，从物种、功能群和群落组织水平上，分析生态系统生产力同物种多样性之间的内在联系，从而揭示该类草地生态系统不同载畜率下物种多样性与生态系统功能的关系，以期为维持草原生态系统的可持续利用提供理论依据。

项目自2013年开始执行以来，严格按照计划任务书的研究内容开展相关的野外和室内研究工作，调查和测定了不同载畜率下草地植物群落的结构、物种组成、生产力动态、生态系统净交换(NEE)和呼吸(ER)、土壤养分状况、 放牧绵羊采食行为和食谱等各项指标，从草地植物功能群及物种多样性变化的角度入手，分析了引起草地稳定性变化的驱动因子和变化机制，提出生长季降水解释了70%以上的草地生产力变异，随着尺度从植物个体到功能群，再到群落水平的变化，生态系统生产力的变异性有降低的趋势。不同载畜率对物种多样性的影响与取样面积有关，随着面积尺度的增加，多样性指数沿载畜率梯度差异性逐渐增大。就土壤理化性质而言，放牧还没有从本质上引起草地生态系统的严重退化。不同载畜率下各个植物功能群之间存在一定的生态补偿效应，调整载畜率可以有效控制草地上不同功能群之间的比例，控制草地上灌木的入侵和生长。这些研究结果为荒漠草原生态系统的可持续利用和生物多样性保育提供了一定的参考数据。