基于MODIS的长江中下游地区植被净第一性生产力时空变化规律

Spatio-temporal variation for vegetative NPP in the lower-middle reaches of the Yangtze River based on MODIS data

基于中等分辨率成像光谱仪（MODIS）数据产品,分析了长江中下游地区的植被净第一性生产力（net primary production,NPP）的时空分布规律,并探讨了气候和土地覆被变化对它们的影响。研究结果表明：在2001-2010年间,研究区植被净第一性生产力的数值主要集中在420-670 g·m^-2·a^-1（以碳计）,平均值为562 g·m^-2·a^-1（以碳计）。从时间角度来看,植被净第一性生产力的年际波动大,且大部分地区的植被净第一性生产力呈现随时间逐渐降低趋势。从空间角度看,植被净第一性生产力呈南高北低、沿海高于内陆的分布规律。研究区内植被净第一性生产力的变化受到了气候因子的综合作用,与年均气温和日照时数呈正相关,与降水量呈负相关（P〈0.05）。同时,土地覆被类型的转变也是导致植被净第一性生产力产生时空变化的重要因素。

Vegetative net primary productivity（NPP） is an important indicator of terrain ecosystem quality. In order to improve the comprehension on vegetation response to human activity and global changes, spatio-temporal characteristics of NPP in the lower-middle reaches of the Yangtze River from Moderate Resolution Imaging Spectroradiometer（MODIS） data were analyzed by GIS technology. Then influential factors affecting these characteristics were explored in the lower-middle reaches of the Yangtze River from 2001-2010. The linear regression coefficients among different annual NPP maps were used to assess the changing trend of NPP and a correlation analysis was also used for the analysis. Results showed that the annual NPP varied from 420 to 670g·m^-2·a^-1, with an average of 562 g·m^-2·a^-1. With respect to inter-annual variation, NPP decreased in most regions, but only 7% regions reached the significance level（P〈0.05）. In regards to spatial distribution, NPP in the southern parts of the region seemed to be higher than in the northern parts, and NPP in coastal regions was higher than inland areas. The correlation analysis revealed that vegetative NPP was significantly sensitive to climate changes（P〈0.05） with annual NPP positively correlated to temperature（r = 0.49） and sunshine duration（r = 0.19） but negatively correlated to precipitation（r =-0.22）. In addition, land cover type transformations also played an important role with vegetative NPP variation. This paper proved that the concentrated human activities and cliamte changes severely affected the natural ecosystems, and might give a deep impression on carbon cycles.