围栏封育对典型草原的级联影响：从叶片功能性状到生态系统功能

It has been estimated that more than 90% of the grasslands in China has been degraded, mainly by heavy livestock grazing. It is urgently needed to restore the community structure and ecosystem functioning of such degraded grasslands. Grazing exclusion is one of the most widely used restoration strategy for degraded grasslands in northern China. The ecological effects of grazing exclusion may range from leaf level to ecosystem level, which are largely remain unknown.Furthermore, it is well-known that grazing exclusion would lead to changes of plant diversity and that biodiversity plays an important role in determining ecosystem functioning. However, changes of biodiversity may be only one of the many pathways through which grazing exclusion alters ecosystem function. The changes of plant functional traits and functional diversity would be a more improtant way than changes of biodiversity through which grazing exclusion would affect ecosystem function. Unfortunately, the role of plant functional traits has been seldom addressed. In this project, we would like to address the effects of grazing exclusion on plant functional traits, leaf nutrient status, community structure and composition,primary productivity, soil nutrient transformation and availability, and ecosystem carbon storage within a grazing exclusion chronosequence in the temperate steppe of northern China. This project will improve our mechanistic understanding of the multi-scale responses of grassland ecosystem to grazing exclusion and the role of plant functional traits in mediating changes of ecosystem functioning. Results from this project will provide robust scientific evidence for the improvement of productivity and carbon sequestration in degraded grasslands.

我国大面积的草地处于不同程度的退化状态，如何恢复其结构和功能并对其进行优化调控成为亟待解决的问题。围栏封育是目前应用最广的退化草地恢复措施，但是对其多尺度上的生态学影响及内在机制知之甚少。已有研究表明围封可以改变生物多样性，进而对生态系统功能产生重要影响。但是，生物多样性的改变仅仅是围封改善生态系统功能的途径之一。围封过程中带来的植物功能性状和功能多样性的变化可能对生态系统功能改善的意义更大。为此，我们选择具有不同围封年限的典型草原群落，运用功能生态学、群落生态学、生态系统生态学、同位素生态学方面的理论、技术和方法，研究不同围封年限对植物功能性状、群落结构与组成、初级生产力、土壤养分转化与供给、生态系统碳储量等生态过程和功能的影响。本项目旨在明确草地生态系统对围封措施的多尺度响应及内在机理，为退化草地生产力和固碳能力的提升提供科学依据。

北方天然草原是我国草地生态系统的重要组成部分，在防风固沙、畜牧业生产等多方面发挥着至关重要的作用。据估计，我国90%的草地处于不同程度的退化状态。如何恢复其结构和功能并对其进行优化调控成为亟待解决的问题。围栏封育是目前应用最广的退化草地恢复措施，但是对其多尺度上的生态学影响及内在机制知之甚少。已有研究表明围封可以改变生物多样性，进而对生态系统功能产生重要影响。但是，生物多样性的改变仅仅是围封改善生态系统功能的途径之一。围封过程中带来的植物功能性状和功能多样性的变化可能对生态系统功能改善的意义更大。为了解决上述问题，本项目以内蒙古锡林浩特的典型草原为研究对象，选择了具有不同围封年限的典型草原群落，综合运用功能生态学、群落生态学、生态系统生态学、同位素生态学方面的理论、技术和方法，研究了不同围封年限对植物功能性状、群落结构与组成、初级生产力、土壤养分转化与供给、生态系统碳储量等生态过程和功能的影响。研究结果显示：与放牧样地相比，围封条件显著提升了群落的生物量、地上凋落物的现存量、改变了植物群落组成、影响到植物的养分利用策略，最终对生态系统的储氮固碳等核心功能产生影响。项目执行四年期间，发表SCI文章9篇和中文核心期刊1篇，培养研究生4人。该项目取得的研究结果揭示北方退化草地围栏封育后的恢复规律和影响因子，为深入了解不同尺度上的草地生态系统特征变化奠定了基础；同时有助于明确草地生态系统对围封措施的多尺度响应及内在机理，为退化草地生产力和固碳能力的提升提供科学依据。