气候变化和人类活动对新疆草地生态系统NPP影响的定量分析

Quantitative analysis of the impact of climate change and human activities on grassland ecosystem NPP in Xinjiang

草地是新疆分布最广泛的植被类型,在陆地碳循环中扮演着重要角色。气候变化和人类活动是影响陆地碳循环的两个重要因素,定量评估气候变化和人类活动对于草地的可持续利用和防止草地退化具有重要意义。以NPP作为指示器,利用实际净初级生产力和潜在净初级生产力定量分析气候变化和人类活动对新疆草地的影响。以2000年作为分界点,将研究时段1982—2015年分成1982—2000年与2000—2015年两部分来比较。研究结果表明:1982—2015年新疆草地以恢复为主。1982—2000年,气候因素是新疆NPP增加的主要因素,气候因素主导的区域占草地总面积的79.41%;2000—2015年,相比于上个时段,人类活动的影响明显加强,人类活动主导的区域占总面积的43.03%。同时,人类活动导致NPP增加的面积占比由18.71%上升到27.87%,主要位于塔里木盆地边缘以及准噶尔盆地西南地区,生态保护工程促进草地的生长。主要由放牧等人类活动导致NPP减少的面积占比由1.78%上升到15.22%,主要位于伊犁河谷、阿尔泰山区南部以及塔城地区。因此,政府应该坚持实施生态保护工程,并对其进行细化和具体化;另外,还需减少伊犁、塔城和阿勒泰等放牧强度过大地区的牲畜量,从而实现草畜动态平衡。

Grassland is the most widespread land cover type in Xinjiang,which plays a significant role in carbon cycle of terrestrial ecosystems.Climate change and human activity are two important factors affecting the terrestrial carbon cycle.Quantitative assessment of climate change and human activities is the critical step which dominates the grassland sustainability and the prevention of grassland degradation and desertification in Xinjiang.This study uses actual net primary productivity(NPP)and potential net primary productivity as indicators to quantitatively analyze the impact of climate change and human activities on Xinjiang grassland.Since the ecological engineering operation started in 2000 over China,the study period was divided into two parts:from 1982 to 2000 and from2000 to 2015.The results showed that climatic factors were the main factors for the increase of NPP in Xinjiang from 1982 to 2000.The area affected by climatic factors accounted for 79.41%of the total grassland area.From 2000 to 2015,the area affected by human activities distinctly extended,and the area accounted for 45.05%of the total area.At the same time,human activities led to the variation of the ratio of the area with the increasing NPP from 18.71%to 27.87%,indicating that the ecosystem protection project achieved its goal.However,human activities led to the variation of the ratio of the area with the decreasing NPP from 1.87%to 15.22%.The reduction of NPP in grassland appearing in the Ili River Valley,the southern Altay Mountains,and parts of the Tianshan Mountains is mainly caused by human activities,such as overgrazing.The protection policies in these areas should be optimized and strictly followed,and the number of livestock should be controlled within a reasonable range.Therefore,the government should insist on the implementation of the ecological protection projects and gradually optimize its refinement and concreteness.In some overgrazing areas,such as Ili,Tacheng,and Altay,reduction of the amount of livestock has to be implemented so as to achieve the dynamic balance of grassland and livestock.