刈割代替放牧是否有利于草地生态系统温室气体减排

The seriously degraded grasslands of China are under enormous pressure of climate change and human activities. With the demand of grassland protection, more and more grazing grass was replaced by mowing. But what and how the impact of mowing altertive grazing on the greenhouse gas is not clear. It is important to clarify what the different grassland management practices impact on greenhouse gas emissions during the grassland response to climate change and human activities. This project will investigate what the effect of mowing alternative grazing on the greenhouse gas emission in Inner Mongolia, North china basing on the field observation in situ and laboratory incubation. Using the C2H2 inhibition technology, static transparent chamer/Li-6400 and static dark chamber-gas chromatography we further reveal the variation regular and generation mechanism of greenhouse gas under different grassland management practices, clarify the mowing intensity on the greenhouse gas warming potential (GWP) in Inner Mongolia. Then we can find the optimal GWP of the mowing intensity, and compared with moderate grazing, to assess whether the mowing instead of grazing will change the greenhouse gas source/sink function of grassland. This study can provide the basis data and parameters for the grassland ecosystem response to human activities and climate change.

我国已严重退化的草地生态系统面临气候变化和人类活动的巨大压力，随着草地保护的需求，越来越多的放牧草地被刈割所取代。搞清不同的草地管理措施对温室气体减排的作用是草地生态系统应对气候变化和人类活动的关键。本项目将以内蒙古多伦站不同时间的围封、围封刈割和放牧样地为研究对象，基于野外原位观测和室内培养实验，应用C2H2抑制技术、静态明箱/Li-cor6400和静态暗箱/气相色谱技术，探讨刈割替代放牧对草地生态系统温室气体通量及其发生过程的影响，揭示内蒙古草原不同草地管理措施下草地生态系统温室气体通量的变化规律与生成机制，阐明不同刈割强度对草地生态系统温室气体综合增温潜势（GWP）的影响。在此基础上，寻找最优刈割强度的GWP并与中度放牧做比较，评估刈割代替放牧是否会改变草地生态系统温室气体的"源/汇"功能，为我国草地生态系统应对人类活动和气候变化提供依据与参数。

近年来，在内蒙古草原地区，刈割已经逐渐取代放牧，成为内蒙古草原最主要的管理措施之一。刈割之后植被群落发生了显著变化，而关于植物群落组成变化如何影响温室气体通量是目前尚未解决的科学议题。我们利用多伦站连续十四年长期刈割的实验平台，基于野外原位观测和室内培养实验，应用静态明箱/Li-cor6400和静态暗箱/气相色谱技术，探讨长期刈割对草地土壤---植被---温室气体互作模式的影响机制；阐明长期刈割草地温室气体通量变化的微生物驱动机制，主要通过改变土壤温度湿度等土壤物理环境的变化而引起微生物量碳氮的变化，进而导致温室气体通量发生变化。进一步的研究还发现合理的刈割高度既能维持草地生态系统的可持续发展，又能最大限度的减排温室气体，对当地牧民合理经营和管理草地具有重要的指导意义。