基于时序NDVI数据的鄱阳湖流域常绿覆被季节性变化特征

选择位于红壤丘陵区的鄱阳湖流域作为研究对象,利用1 km×1 km分辨率的时序SPOT4-VEGETATION数据,对流域内典型土地覆被--常绿覆被的绿度值、峰值、谷值、年均NDVI(NDVI-I)和NDVl年内极差(NDVIMM)等特征值进行了提取.在此基础上,探讨了不同常绿覆被类型的NDVI指数年内季节变化规律.结果表明:时序NDVI指数基本上能够较好地刻画不同常绿覆被类型之间的差异性,植被指数NDVI特征值随覆被的类型及其生长状态有规律地变化,即NDVI年均值和最小值基本上按"常绿阔叶林＞常绿针阔叶混交林＞常绿针叶林＞常绿针叶一落叶混交林"的顺序变化;典型常绿阔叶林的NDVI指数年内变化曲线基本上没有大的起伏波动;常绿针叶林以及常绿针阔叶混交林占主导地位的常绿混交林NDVI指数年内变化比较和缓,但常在8月和11月有所波动;以常绿针叶林为主、但有较多落叶林混杂其中的常绿混交林,其NDVI指数年内变化曲线基本上呈和缓的单峰型波动.

SEASONAL VARIATION OF EVERGREEN LAND COVERAGE IN POYANG LAKE WATERSHED USING MULTI-TEMPORAL SPOT4-VEGETATION DATA

Evergreen land coverage is the typical type of landscape in Poyang Lake watershed,accounting for 40.05% of whole landscape.It includes three main types,i.e.evergreen broadleaf forest,evergreen needleleaf forest and evergreen mixed forest.By using multi-temporal SPOT4-VEGETATION sensor data,this paper analyzed the characteristic values of the evergreen land coverage,such as greenness value,crest value,trough value,integral of NDVI(NDVI-I),difference between the maximum and minimum NDVI(NDVI-MM),etc.Both NDVI-I and minimum NDVI vary as "evergreen broadleaf forest>needle and broad-leaved mixed evergreen forest>evergreen needleleaf forest>needleleaf and deciduous mixed evergreen forest".The annual NDVI curve in typical evergreen broadleaf forest had no obvious change,while needleleaf and deciduous mixed evergreen forest had a single peak.