基于时序NDVI数据的鄱阳湖流域常绿覆被季节性变化特征

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

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NDVI年内极差(NDVI-MM)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—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。

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 broadqeaved 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.