中国北方典型荒漠区生长季降水特征和归一化植被指数的关系

Correlation between Precipitation and NDVI in Vegetation Growing Season in a Typical Desert in North China

植物生长季内的降水变化是造成植物生长产生年际变异的重要因素,降水量、分配方式以及集中程度和时间是降水变化的重要特征。利用2000-2017年的MODIS归一化植被数据集和4个样点植物生长季(5-9月)的日降水数据,分析了研究区NDVImax与降水特征的相关性。结果表明:2000-2017年研究区4个样点的NDVImax均呈上升趋势;生长季降水量呈现出两侧降水增加,中间降水减少的趋势;降水集中度(PCD)西部增高,东部降低;研究区的降水集中期(PCP)都有延后的趋势。4个地区中除榆林外,其他3个地点的PCD与PCP对NDVImax的影响均大于生长季降水量,说明这3个地点的NDVImax值的年际变化主要取决于PCD与PCP的变动,且均为正相关关系,即降水越集中越有利于NDVImax的增加;榆林地区的NDVImax与生长季降水量的偏相关结果为正相关,与PCD为负相关,且与生长季降水量的相关性最强,说明该地区植物对生长季降水量更敏感,降水越均匀越有利于该地区植物的生长。

Precipitation change in vegetation growing season is an important factor causing inter-annual fluctuation of vegetation growth.The correlation between NDVImax and precipitation in vegetation growing season in a typical desert in north China was analyzed using the MODIS normalized vegetation dataset and the daily precipitation data from May to September during the period of 2000-2017.The results indicated that the values of NDVImax in four sample plots in the study area were in an increase trend from 2000 to 2017.Precipitation in the study area in vegetation growing season was in an increase-decrease-increase trend.The precipitation concentration degree(PCD)was high in the west but low in the east,and it became later in the study area.In addition to Yulin,the effects of PCD and PCP on NDVImax in other three sample plots were higher than that of precipitation,which revealed that the interannual fluctuation of NDVImax values in these sample plots was mainly affected by the changes of PCD and PCP,and there were the positive correlations among them.In Yulin,however,the NDVImax had a positive correlation with the precipitation in vegetation growing season,but a negative one with PCD,and its correlation with the precipitation in vegetation growing season was the highest,indicating that the vegetation growth to precipitation in vegetation growing season was more sensitive.