环青海湖地区草地对气候变化和人类活动的响应

Responses of grassland to climate change and human activities in the area around Qinghai Lake

以环青海湖地区为研究区,基于MODIS NPP数据、气象数据和Thornthwaite模型,估算了草地实际净初级生产力(actual net primary productivity,简称NPP_A)和潜在净初级生产力(potential net primary productivity,简称NPP_P),并将NPP_P和NPP_A的差作为人类活动对净初级生产力的影响(net primary productivity influenced by human,简称NPP_H),在此基础上,分析了草地NPP_A的时空变化以及气候变化和人类活动对草地的影响。结果表明:2000—2015年,环青海湖地区的年均草地NPP_A为176.93 g C·m^(-2)·a^(-1);16年来环青海湖地区草地NPP_A呈波动增加趋势,在空间分布上,草地NPP_A从西到东呈逐渐增加的态势;16年来环青海湖地区87.42%的区域草地发生恢复,12.58%的区域发生退化,总体上草地以恢复为主;在气候变化和人类活动对草地恢复的影响中,由气候变化主导草地恢复的比例为10.98%,由人类活动主导草地恢复的比例为5.27%,而人类活动和气候变化共同主导草地恢复的比例为83.75%,气候变化和人类活动的共同作用是草地恢复的主导力量;在气候变化和人类活动对草地退化的影响中,仅由气候变化主导草地退化的比例为6.28%,由人类活动主导草地退化的比例为50.75%,两者共同主导的草地退化的比例为42.97%。可见,草地的局部退化主要是由于不合理的人类活动导致的,如过度放牧、草地开垦和土地覆盖变化等。

The actual(NPPA)and potential(NPPP)net primary productivity in the area around Qinghai Lake were calculated based on MODIS NPP data,meteorological data and Thornthwaite model.The difference between NPPPand NPPAwas used to quantify the impacts of human activities on net primary productivity(NPPH).The temporal and spatial changes of grassland NPPA,as well as the effects of climate change and human activities on grassland were analyzed.From2000 to 2015,the average NPPAwas 176.93 g C·m-2·a-1.In addition,NPPAexhibited a generally increasing trend between 2000 and 2015.In terms of spatial distribution,NPPAincreased gradually from west to east.87.42%of the grasslands were restored,whereas only 12.58%were degraded between 2000 and 2015.For the effects of climate change and human activities on grassland restoration,the climate change,human activities and their combined effect of climate change and human activities contributed to 10.98%,5.27%and 83.75%,respectively.For the effects of climate change and human activities on grassland degradation,the climate change,human activities and the combined effect of climate change and human activities contributed to6.28%,50.75%,and 42.97%,respectively.It is concluded that the grassland degradation in this area was mainly caused by irrational human activities,such as overgrazing,grassland reclamation and land cover change.