气候变化和人类活动对我国典型草原区植被恢复的影响

草原区作为影响我国陆地生态系统碳水循环和生态安全的重点区域，对气候变化和人类活动极为敏感.然而，有关气候变化和人类活动对该区域植被恢复相对贡献的认识尚存分歧.以生态系统净初级生产力(NPP)为评价指标，通过对比MODIS观测的实际NPP和基于Thornthwaite Memorial模型估算的潜在NPP的趋势差异，量化了2000～2020年气候变化和人类活动对我国典型草原区(北方温性草原区和青藏高原高寒草原区)植被恢复的相对作用.结果表明，研究区内93%的草地植被呈恢复趋势，NPP平均增加速率达(以C计)2.12 g·(m²·a)^-1(P<0.01),其中，近一半植被恢复区受气候变化和人为活动共同控制，约36%和10%植被恢复区分别受气候变化和人类活动的独立控制；此外，不同草地类型气候变化主导植被恢复的面积占比差异大，主要表现为高寒草地明显高于温性草地，气候条件越干旱，气候主导面积占比越大.人类活动不是北方温性草原区和青藏高原高寒草原区植被恢复的主要原因，但在气候条件恶化地区，人类活动可降低甚至抵消气候变化对植被的负面影响.未来需加强长...

Impacts of Climate Change and Human Activities on Vegetation Restoration in Typical Grasslands of China

Grasslands, as one of the key ecosystems relevant to the terrestrial ecosystem carbon and water cycles as well as the ecological security in China, are very sensitive to climate change and human activities. However, the relative contributions of climate change and human activities on the vegetation restoration in those regions are still controversial. Using ecosystem net primary production (NPP) as an ecological indicator, this study quantified the relative roles of climate change and human activities on vegetation restoration in Chinese typical grasslands (northern temperate grasslands and Qinghai-Tibet Plateau alpine grasslands) by comparing the trends of actual NPP derived from MODIS and potential NPP estimated by the Thornthwaite Memorial model during 2000-2020. The results showed that approximately 93% of the grasslands in the study area experienced a recovering tendency, with an average increase of NPP (carbon) by 2.12 g·(m²·a)^-1(P<0.01). Therein, nearly half of the vegetation-restored areas were jointly-dominated by climate change and human activities, whereas approximately 36% and 10% of the restored areas were controlled individually by climate change and human activities, respectively. In addition, the share of climate-change dominated areas differed greatly by grassland types, characterized by a much larger area percentage in the alpine grasslands than that in the temperate grasslands and an increasing area share with a drying background climate. This study suggested that human activities were not primarily responsible for the vegetation restoration in northern temperate grasslands and Qinghai-Tibet Plateau alpine grasslands, but they could decrease and even cancel the possible vegetation degeneration caused by worsening climate in a few regions. Long-term monitoring of vegetation dynamics and a multi-method comparison are needed in future studies.