关键词: 植被覆盖, 时空变化, 相关性, 西南地区

Abstract: The vegetation is important to maintain the ecological environment in the earth, and it is affected by climate factors significantly. Dynamic monitoring of the vegetation variation could reflect the trend of climate change to some extent. Vegetation cover change is one of the cores of global environmental change research, but also the front and hot field of modern physical geography. SPOT AVHRR NDVI (Normalized Difference Vegetation Index) in the Southwest during the period from 1999 to 2012 was selected to get the vegetation cover change information based on GIS and RS technology. The temporal and spatial vegetation cover change were analyzed by using spatial data covering the Southwest in the past 14 years, and discussed the relationship between major climatic factors (temperature, precipitation and SPEI) and the vegetation. The results are shown as follows. (1) From 1999 to 2012, NDVI vegetation of the Southwest had an entirely rising trend, with the growth of 6.9%/10 a, and this was faster than average of China. There were some significant spatial differences of the vegetation cover change, and the NDVI of the seven vegetation types increased significantly. Meanwhile the vegetation coverage appeared improvement as a whole area. The NDVI decreased area covered only about 1.18% of the whole study area. The decreased area was mainly distributed on the north of Hengduan Mountains, the east of Sichuan Basin and the central part of Yungui Plateau. (2) The Hurst index of NDVI time series shows that the vegetation restoration was sustainable, and it is expected that the area of vegetation cover change to healthy development, but the NDVI decreased areas with strong persistence and the NDVI increased areas with weak persistence might be indicative. Grassland degradation & strong sustainability area is the largest, as well as the improvement of the mixed needle & strong sustainability area. The decreased areas with strong persistence was mainly distributed on the north-central of Hengduan Mountains, the Midwest of Yungui Plateau, zoige plateau central, and northern Sichuan basin intersect with the Zoige plateau area. (3) In the past 14 years, the climate of the Southwest presented a process of distinct warming and drying. Analyzing the space distribution principle of temperature, the annual average temperature raised overall in the Southwest, meanwhile west of the Southwest has an entirely rising trend and East was opposite. Precipitation and drought trend was decreased in South and the North of the area is increased. There was significant positive correlation between NDVI and temperature, and precipitation was not strong correlated relatively with NDVI in the Southwest, and precipitation was the key to affect vegetation growth on the study area. In addition, no significant correlation between SPEI and NDVI could be found in the Southwest.

Key words: vegetation coverage, temporal and spatial change, correlation, the Southwest