中文摘要：

采用改进的CASA模型估算2001-2012年西北干旱区陆地生态系统的净第一性生产力（NPP），采用线性趋势分析、标准差和Hurst指数等方法，分析了NPP的时空变化特征。结果表明：研究区的NPP表现出很强的季节性变化规律，7月份NPP为最高值，12月为最低值，12年间NPP的年均值整体上呈现增加的趋势，但波动较大，最低值出现在2006年，最高值出现在2012年。NPP稳定性存在显著的地域差异，内蒙古温带草原区的NPP改善最为明显，新疆山地草原针叶林区的NPP退化最为严重，西北温带暖温带荒漠区NPP变化相对稳定。研究区NPP变化总体呈中强持续性特征，中强持续性区域占研究区总面积的比重达77．5％；NPP变化以良性发展为主，强持续性的退化区和弱持续性的改善区需要关注，二者合计占研究区总面积的15．9％。

英文摘要：

The ecosystem net primary productivity （NPP） in the arid region of Northwest China during the period of 2001-2012 was calculated by using an improved CASA model. Spatial-tem- poral characteristics of NPP were analyzed by employing linear trend analysis, standard deviation and Hurst index. The results showed that NPP in the study region had a strong seasonal variation, with a maximum in July and a minimum in December. Temporally, the vegetation NPP showed an increasing trend from 2001 to 2012 with a large fluctuation （lowest in 2006 and highest in 2012）. The NPP values varied spatially. The most obvious increase of NPP took place in the temperate steppe region of Inner Mongolia, while the greatest decline of NPP occurred in the mountain grassland-coniferous forest region of Xinjiang, and the NPP was relatively stable in the temperate and warm-temperate desert region of Northwest China. Hurst index analysis showed that the over- all change of NPP in the study region showed moderate-strong continuity characteristics, and the area with moderate-strong continuity accounted for 77.5% of the study region. The NPP variation mainly showed a tendency of healthy development. However, attention needs to be paid to 15.9% of the study region in which the NPP was continuously degraded or only slightly improved.