1982-2006年中国东部秋季植被覆盖变化过程的区域差异

为进一步认识1982-2006年中国东部秋季植被覆盖变化过程及其区域差异,论文分析了1982-2006年9-10月归一化差值植被指数(NDVI)的多年平均状况和年际变化,并通过聚类分析辨识了NDVI变化过程的主要模态,进而探讨了它们与温度和降水变化的相关关系。结果表明:(1)中国东部秋季森林的覆盖度最高,农田次之,草原最低,并表现出1998年之前趋于增加、此后趋于锐减的变化特征;(2)不同区域植被覆盖变化过程不尽相同,整个研究区植被覆盖变化过程可以分为6种模态,其中①东北地区呈波动上升趋势,②内蒙古高原东北部1982-1998年波动上升、1998年后陡然降低,③华北北部-东北南部呈现跃迁式上升,跃迁年份为1994年,④华北南部表现为先降低后略微增加,趋势转折出现在2000年,⑤江淮地区呈现为1982-1992年波动增加、1992-2006年波动降低,⑥长江及其以南地区表现为陡然下降,突变始于2000年;(3)除了内蒙古高原东北部降水变化能够解释植被覆盖度年际变率的66%以外,华北北部-东北南部的植被覆盖与降水具有正相关关系,秦岭-大巴山-长江中下游及以南地区的植被覆盖与同期温度呈显著正相关,但是降水或温度仅能够解释植被覆盖年际变率的21%,其余地区植被覆盖与气候变化没有显著的相关关系。

Spatial Differences of Variations in Autumn Fractional Vegetation Coverage in Eastern China during 1982-2006

To understand the variations in fractional vegetation coverage (FVC) over eastern China in autumn during 1982-2006 deeply, we analyzed the mean spatial pattern of Normalized Difference Vegetation Index (NDVI) in autumn, discriminated the models of variations in autumn NDVI during 1982-2006 by cluster analysis and studied the correlations between variations in autumn NDVI and temperature and precipitation. The results show that: 1) The mean FVC over eastern China in autumn decreased spatially in the order of forest, farmland and grassland, and it is obvious that the regional mean FVC increased before 1998 while decreased thereafter. 2) During 1982-2006, different regional FVC changes were marked by large differences. The variations in FVC within the study area could be summarized as 6 models, which consist of a rising trend with fluctuations in Northeast China, a rising trend with fluctuations before 1998 and a sharp drop thereafter in the northeast of Inner Mongolia Plateau, a sharp transition from mean lower FVC to higher FVC in 1994 in the north of North China and the south of Northeast China, a conversion from a decreasing trend during 1982-2000 to slight rising trend after 2000 in the south of North China, a conversion from a rising trend with inter-annual fluctuation before 1992 to a decreasing trend with inter-annual fluctuation thereafter in Jiang-Huai area, a sharp transition from mean higher FVC to lower FVC in 2000 in the Yangtze River and areas south of it. 3) Excepting for the northeast of Inner Mongolia Plateau where FVC was significantly correlated with precipitation and 66% of inter-annual variation in FVC could be explained by precipitation, a positive significant correlation between FVC and precipitation could be found in northes of the North China and the south of Northeast China and a positive significant correlation between FVC and temperature could be found in areas along Qinling-Daba Mountains-middle reaches of the Yangtze River, however, temperature or precipitation could only explain 21% of inter-annual variation in FVC; in addition, no significant correlation between FVC and temperature/precipitation could be found in the others regions.