基于SPOT-VGT数据的流域植被覆盖动态变化及空间格局特征--以淮河流域为例

Dynamic changes and spatial patterns of vegetation cover in a river basin based on SPOT-VGT data:A case study in the Huaihe River Basin

为探明近10多年来淮河流域的植被覆盖状况动态变化及其空间格局,本研究基于SPOT-VGT的NDVI数据和淮河流域土地利用/覆被数据,利用ArcGIS空间分析工具,设计植被动态空间计算模型,分析了1999-2007年淮河流域植被变化的时空格局,包括年内各月变化规律、年际变化趋势、不同景观类型的植被指数特征及其变化趋势等。结果表明:①SPOT-VGT数据结合GIS空间分析和建模工具,可以较好的计算和分析流域尺度的植被状况时空格局;②淮河流域绝大部分地区(71.33%)在1999-2007年NDVI有显著增加趋势,表明流域整体植被覆盖明显改善;③淮河流域NDVI年内变化曲线呈双峰型,4月份和8月份分别出现波峰,8月波峰高于4月;④淮河流域植被覆盖状况空间差异显著,NDVI多年平均值的空间格局为:平原地区较高,淮河干流北岸高于南岸;山丘区差异较大,大别山区植被指数最高,沂蒙山区植被指数最低,水土流失风险较高;大中城市及其周边地区,植被指数低;⑤不同景观类型的NDVI多年变化趋势存在一定的差异:耕地、林地、草地、盐碱地的平均值增长趋势显著且较为平稳。滩地在波动中有小幅度增长;沼泽地波动幅度最大。本研究可为淮河流域森林保育、水土流失防治等措施的制定提供科学依据。

To investigate the dynamic changes and spatial patterns of vegetation in the Huaihe River Basin, this study used SPOT-VGT NDVI （Normalized Different Vegetation Index） data and land use/cover data to analyze the spatial-temporal patterns of vegetation change in the region during 1999 to 2007 by using ArcGIS Spatial analysis tools. The results showed that： （I） SPOT-VGT data, combined with GIS Spatial analysis tools and models, can be used in the calculation and analysis of vegetation cover conditions in river basin scale; （2） NDVI maintained an clearly increasing trend in most areas （71.33%） of the Huaihe River Basin during 1999-2007, suggesting that the vegetation coverage was improved in the region in the last decade, which indicated that the measures of vegetation protection and restoration had achieved positive results; （3） Monthly NDVI variations showed a double-peak curve. The two peaks appeared in April and August respectively, and the peak in April was lower than that in August; （4） The average NDVI showed obvious spatial variations. NDVI in the plain areas was higher than that in the mountain areas, and it was higher in the north areas of Huaihe River than in the south areas; NDVI varied greatly in the mountain areas, with the highest average value in the Dabieshan Mountain and the lowest in the Yimengshan Mountain. Areas in and around the cities had lower NDVI due to high density of built-up land. The areas with relatively poor vegetation coverage had high risk of soil erosion. （5） The NDVI changing trends varied among different land use/cover types. The average NDVI values of cropland, woodland, grassland and alkaline land had shown a stable increasing trend during 1999-2007. The average ND VI of flooded plains land showed a slightly increasing trend. The ND VI of marshes fluctuated dramatically. The results of the studies of dynamic changes and spatial pattems of vegetation in the Huaihe River Basin can provide a scientific basis for planning and taking measures to protect watershed forest, and in turn to control soil erosion.