西南地区近14a植被覆盖变化及其与气候因子的关系

基于1999~2012年NDVI数据,结合气温和降水资料,运用GIS和RS技术,分析了西南地区近14a植被覆盖的时空变化特征及与气温、降水的关系。结果表明:(1)该区植被生长良好,各植被类型NDVI均呈显著增加趋势。空间整体表现为改善状态,改善面积远大于退化面积,严重退化区仅占1.18%。退化区分布于横断山地北部、四川盆地东部以及云贵高原中部。(2)植被覆盖变化将以良性发展为主,但强持续性的退化区和弱持续性的改善区应值得关注;强持续性的退化区主要分布在横断山地中北部、云贵高原中西部、若尔盖高原中部、四川盆地与若尔盖高原相交区域;草原强持续性的退化面积最大,针阔混交林强持续性的改善面积最大。(3)NDVI与温度存在明显的正相关关系,而与降水及干旱指数变化的关系不太明显,温度是影响该区植被变化的主要自然因素。

VEGETATION COVER CHANGE OVER THE SOUTHWEST CHINA AND ITS RELATION TO CLIMATIC FACTORS

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 SPED 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.