内蒙古草原植被生产力稳定性的时空格局及其影响因素

Ecosystem stability plays an essential role in maintaining the ecosystem function and services and has been attracting wide attention in the context of global environmental change. Because primary productivity is a key dimension of ecosystem function, ecosystem stability has been frequently measured by the temporal stability of productivity, defined as the ratio of the temporal mean of productivity to its temporal variability as measured by its standard deviation. Numerous plot-scale experiments have shown that reduced plant diversity leads to decreased temporal stability of productivity because of reductions in compensatory dynamics or in asynchronous responses to environmental fluctuations. However, there is an urgent need to extend existing knowledge to larger spatial scales to match the scale of management and conservation. Being the second largest natural pasture in China, the Inner Mongolia steppe has been subjected to significant climate change and anthropogenic disturbances and shown a trend of widespread degradation. Although the temporal stability of productivity greatly influences the sustainability of local graziery, large uncertainty remains in the current status and temporal trends of productivity stability in Inner Mongolia steppe. By integrating datasets of remote sensing imagery, climate and field community survey, this program aims to analyze the current status of productivity stability across the Inner Mongolia steppe and its temporal trends during 1982-2016 and assess the driving effects of climate change and grassland degradation. This work will not only gain a better understanding of the temporal-spatial patterns and the mechanisms of large scale productivity stability but also help to improve the management and development of the steppe in Inner Mongolia.

生态系统稳定性对于维持生态系统功能和服务具有十分重要的意义，是生态学研究的热点问题之一。生产力是生态系统最重要的功能之一，因而生产力稳定性是衡量生态系统稳定性的一个关键指标。以往关于生态系统稳定性的研究往往基于样地尺度，在较大空间尺度上对稳定性相关理论的验证和拓展仍相对缺乏。内蒙古草原是我国第二大天然草场，受气候变化和过度放牧等人为因素的影响，出现不同程度的退化。生产力稳定性对内蒙古草原畜牧业的可持续发展有着重要影响，然而其大尺度格局和相关影响因素仍不清楚。本项目拟综合多源遥感数据、气候数据以及地面样方调查，分析内蒙古草原植被生产力稳定性的大尺度格局及其在过去几十年中的变化趋势，阐明气候变化、物种多样性以及草地退化对内蒙古草原植被生产力稳定性的影响。本项目不仅有助于推动生态系统稳定性相关理论在大尺度上的应用和拓展，也将为内蒙古地区草地资源可持续管理和草牧业健康发展提供重要的理论依据。

由于气候变化和过度放牧等人为因素的影响，蒙古高原（我国内蒙古自治区和蒙古国）草地植被草原植被发生了不同程度的退化。研究表明，生态系统退化可能会导致植被生产力稳定性降低，即植被活动的年际变异程度不断增加。然而，蒙古高原草地植被稳定性的大尺度格局及其在过去30年来的变化目前尚不清楚。本项目首先定义了大尺度植被活动稳定性的三个表征指标，包括物候起始、结束期以及植被生产力的年际变异程度，并基于遥感植被指数估算了1983-2015年稳定性表征指标的大尺度时空格局及其对气候变化的响应，同时结合野外调查数据，分析了植物群落特征和土壤养分状况对草地植被生产力稳定性的影响。主要研究结果如下：（1）过去几十年，蒙古高原草地植被活动稳定性显著下降，研究区41%的地区植被生产力年际变异程度随时间显著增加，呈现出不稳定性。（2）气候变暖、干旱和气候因子年际变异性共同解释了植被活动稳定性下降趋势的60-80%；相比气候因子的年际变异性，气候变暖和干旱对研究区草地植被活动稳定性降低的贡献更大。（3）草地群落物种多样性和土壤养分状况与植被生产力稳定性显著相关，但是这种相关性在不同草地类型间存在明显差异。本项目研究结果既有助于深入认识气候变化对草地植被生态系统的影响，也可为草原畜牧业可持续管理提供理论依据。