1982——-2010年全国草地生长时空变化

基于遥感技术, 利用1982---2010年间NOAA-AVHRR卫星获得的归一化植被指数(normalized difference vegetation index, NDVI)数据对全国29年来的草地生长动态变化及其与温度、降水的相关关系进行分析。结果表明: 29年来, 全国草地生长季NDVI总体上呈显著增加趋势(R²=0.25, p<0.01), 尤其是在1982?1999年间(R²=0.60, p<0.01), 而自20世纪90年代末开始失速。值得注意的是, 最近十几年(1999---2010年)草地生长季NDVI变化趋势的大小和方向基本上取决于起始年份的选择, 因而这一阶段草地生长的总体趋势不显著。不同地区、不同时段生长季NDVI变化趋势的空间分布存在较大差异。草地生长在1982---1999年间呈广泛(约占85%)增加趋势, 在1999---2010年间出现较大范围(约占50%)的逆转, 尤以干旱、半干旱地区的草地植被生长下降趋势最明显。水热组合状况是影响这一变化的主要原因。生长季平均NDVI与气候因子之间的相关关系分析表明, 全国大部分地区草地生长变化主要受降水驱动, 对于部分高寒和湿润、半湿润地区的草地, 生长季NDVI与温度关系密切, 温度上升对该地区草地生长有利。

NDVI-Based Spatial-Temporal Change in Grassland Growth of China from 1982 to 2010

The authors used remote sensing data (NOAA-AVHRR) and took the Normalized Difference Vegetation Index (NDVI) as an indicator of vegetation growth to explore the trends of grassland growth and their dynamic responses to climate change from 1982 to 2010. Overall, during the 29 years, the national averaging growing season NDVI significantly increased (R²=0.25, p<0.01), especially during the period 1982?1999 (R²=0.25, p<0.01). This trend, however, was stalled since the late 1990s. Furthermore, as for the trend over the period 1999?2010, its magnitude or even the sign of change substantially depended on the choice of the beginning year. This suggests a non-significant trend in China’s grassland growth over this period. The trends of growing season NDVI also showed remarkably spatial-temporal differences. The extensive grassland greening trend that occurred during the earlier study period 1982?1999 appeared a wide-range reversal during the following study period 1999?2010, especially in the arid and semi-arid regions. The condition of hydro-thermal combination was the main factor controlling these growth changes. Correlation analysis between growing season NDVI and climate factors showed that in most parts of grasslands in China, the vegetation growth was rather driven by precipitation than by temperature. While for the grasslands in alpine regions and humid or semi-humid regions, the growing season NDVI correlated closely to temperature, indicating that warming exerted a positive effect on grassland growth in these areas.