干旱对河西走廊植被净初级生产力的影响

干旱对生态系统碳循环具有重要影响，随着气候变暖，全球干旱事件频率不断上升，研究干旱对植被净初级生产力的影响具有重要意义。提高植被净初级生产力（NPP）的时间分辨率是认识干旱对其影响机制的重要途径。基于5天NDVI遥感数据，以河西走廊为研究区，利用CASA模型估算2010—2015年5天步长尺度的NPP，将5天降水为零定义为干旱基本单元，利用标准分数来探究干旱对植被NPP的影响。结果表明：基于高时间分辨率遥感数据能有效探测干旱对NPP的影响机制，研究期间河西走廊年干旱频次6—44次，干旱对该地NPP有负效应，对5天均值的影响为-0.23 g·m^-2，影响幅度为-1.93%，整体影响较小。干旱对林地NPP影响最大，下降3.70%，草地次之，荒漠最小。随着干旱持续时间的增加，NPP变化趋势呈现为先降低，然后降低趋势增加，最后趋于稳定的过程。干旱对夏季的NPP影响最大，冬季最小，秋季干旱对林地影响最大。

Impact of drought on net primary productivity of vegetation in arid and semi-arid areas:a case study of Hexi Corridor

Drought has an important impact on the carbon cycle of the ecosystem.With the global warming increasing the frequency of drought events,it is of great significance to study the impact of drought on the net primary productivity of vegetation.Improving the time resolution of the net primary productivity of vegetation is an important way to understand the mechanism of drought on NPP.Based on the five-day NDVI remote sensing data,this paper uses the Hexi Corridor as the research area and uses the CASA model to estimate the five-day step scale NPP from 2010 to 2015,The five-day precipitation is defined as a basic unit of drought,using standard scores to explore the impact of drought on vegetation NPP.The results show that based on high-resolution remote sensing data,the effect mechanism of drought on NPP can be effectively detected.During the study period,the frequency of drought in the Hexi Corridor averaged 6 to 44 times,-0.23 g·m^-2·yr^-1,the impact amplitude is-1.93%,the overall impact is small.Drought has the greatest impact on forest land,at 3.70%,followed by grassland,and desert is the least.As the duration of the drought increases,the NPP change trend is a process of decreasing first,then decreasing,and finally stabilizing.Drought has the greatest impact on NPP in summer,the smallest in winter,and the greatest impact on forest land in autumn.