基于GIS缓冲区功能的塔里木河中游植被指数时空变化分析

Spatiotemporal Variation of NDVI in the Middle Reaches of the Tarim River Based on GIS Buffer Function

塔里木河中游的输水堤防工程束缚了汛期洪水漫溢,提高了下游输水效率。与此同时,堤防工程的修建也给塔里木河两岸生态带来了一些影响。本文以塔里木河中游输水堤外天然植被为研究对象,借助于遥感处理技术和GIS缓冲区分析功能,对塔里木河中游2000年（建堤前）和2010年、2014年（建堤后）天然植被指数（NDVI）时空变化以及土地利用变化进行了比较分析。结果显示：因河水影响范围限制,天然植被NDVI随着距堤防距离的增大而呈减小趋势。就离堤防2 000 m的范围来看,除了距堤防600-800 m的地区,2000年NDVI值整体上高于2010年;在离堤防20 km的范围内,前10 km左右,2000年的NDVI值比2010年要大,在10 km范围之外,受人类活动的影响,河水的天然影响被弱化,2010年的NDVI反而大于2000年。从土地利用变化上看,2014年研究区耕地面积是2000年的9倍左右,植被面积减少11.22%,较多天然林地转变为耕地。

Hydrological conditions affect the development of riparian ecosystems in sensitive watershed. The waterconveyance embankment project constrains overflow in the middle reaches of the Tarim River in flood season and improves the water conveyance efficiency downstream. However,the project also brings about some ecological problems. In this paper,the natural vegetation along the middle reaches of the Tarim River was regarded as the research object,and the changes of normalized differential vegetation index（ NDVI） and land use in 2000（ before the project） and 2010 and 2014（ after the project） were comparatively analyzed using the remote sensing and GIS means.The results showed that the NDVI of natural vegetation decreased with the increase of the distance away from the embankment. The NDVI value in a 2 km wide zone away from the embankment in 2000 was holistically higher than that in 2010 except that in a 600-800 m wide zone; in a 20 km wide zone away from the embankment,the NDVI value around a 10 km wide zone in 2000 was higher than that in 2010,on the contrary,it in a zone further than 10 km away from the embankment in 2010 was higher than that in 2000 due to the increase of human activities and the decrease of the effect of natural factors on vegetation. Viewing from the land use change,the area of cultivated land in the study area in 2014 was about 9 times of that in 2000,the vegetation area was reduced by 11. 22%,and some natural forest land was transformed into farmland.