广西近15a植被覆盖变化及其对气候因子的响应

Spatial-temporal variations of vegetation cover and its response to climate factors in Guangxi over the past 15 Years

基于1998-2012年SPOT VEGETATION逐旬NDVI数据、气象站点的降水量和温度数据,采用趋势分析法、标准差、Hurst指数和相关系数法,研究了广西NDVI时空变化特征及未来趋势,并分析了NDVI与前0-3个月降水量和温度相关系数的最大值及其对应的滞后期。研究表明:1)近15 a来,研究区NDVI年际变化呈增加趋势,且岩溶区NDVI的增加速率稍快于非岩溶区;2)NDVI均值表现出四周高、中间低,非岩溶区高于岩溶区的总体特征,NDVI总体以中等-低波动为主;3)NDVI改善的区域面积占96.62%,岩溶区改善的面积比例略低于非岩溶区;Hurst指数为持续性的区域面积占95.26%,岩溶区持续性区域面积小于非岩溶区;未来植被覆盖总体呈现持续性改善趋势;4)NDVI与前2个月降水量和前1个月温度的相关系数最大,NDVI对降水量和温度最大响应的滞后期分别为2-3个月和1-2个月;岩溶区植被生长对降水量和温度变化更敏感;不同植被类型受降水量和温度的影响程度及其响应时间具有差异性,而同一植被类型对温度变化的响应时间比降雨量短。

This paper analyzes the spatial and temporal variation of NDVI and its response to climatic factors in Guangxi during 1998-2012 by using trend analysis, standard deviation, Hurst index, and correlation coefficient methods. The analyzed data including SPOT VEGETATION NDVI data and temperature/ precipitation data were collected from meteorological stations. The results indicated that： 1） The annual NDVI increased from 1998 to 2012, with the increasing rate of the karst region being slightly faster than the non-karst region; 2） the spatial distribution of mean NDVI was low in the center and high in the periphery, and the karst region was lower than the non-karst region; the fluctuation of NDVI varied from medium to low. 3） areas with improved NDVI values accounted for 96.62% of the total, and those areas were slightly lower in the karst region compared with the non-karst region; the areas where Hurst index was sustainable occupied 95.26% of the total, and those areas were lower in the karst region than the non-karst region; The overall vegetation coverage in the future showed a trend of continuous improvement. 4） The correlation coefficient between NDVI and the preceding 2 months’ precipitation and the preceding 1 month’s temperature were the maximum; the maximum lag time of NDVI to temperature and precipitation were 1 to 2 months, and 2-3 months, respectively. Vegetation in the karst area was more sensitive to the variation of precipitation and temperature. The influence degree and the response time among different vegetation types were different, and the same vegetation type’s response time to the variation of temperature was shorter than that of precipitation