东洞庭湿地植被格局变化及其影响因素

东洞庭湖(也称东洞庭)湿地植被格局的变化特征及其影响因素的分析是该地区湿地植被保护与恢复策略制定的基础。基于美国陆地资源卫星Landsat TM/ETM+数据,应用决策树分类法分别提取东洞庭湖1999年、2002年、2006年三个时期湿地景观信息,通过转移矩阵法和质心迁移法对植被的时空演变分析。结果表明:(1)1993～2002年东洞庭湖芦苇、林地、苔草滩地面积均有所增加,芦苇增长速度最快,年均增长面积为28.93km²;2002～2006年林地面积迅速增加,年均增长面积为29.655km²,苔草面积有所减少,芦苇面积保持基本稳定;(2)东洞庭湖湿地植被质心呈现从林地—芦苇—苔草逐层靠近湖心的分布特点,1993～2006年三种植被类型的质心均不断向湖心迁移,其中以林地与芦苇的变迁更为显著。

Vegetation pattern changes and their influencing factors in the East Dongting Lake wetland

The bases for the protection of wetland vegetation cover and for the design of vegetation recovery initiatives is an available vegetation cover framework,including the variational characteristics and the investigation of factors influencing vegetation variability.In this paper,using Landsat TM/ETM+ data,we developed a decision framework for the extraction of wetland landscape information from three periods for East Dongting Lake.We then performed analyses of the changes of vegetation on the basis of transfer matrix and the centriods shifting method.Results are shown as follows.(1) From 1993~2002,the areas of forested land,reed land,and carex covered area increased,among them the reed land increased fastest,with an annual growth of 28.93 km².During 2002~2006,forested land increased rapidly,with an annual growth of 29.655 km²,while the carex area decreased,and reeds remained unchanged.(2) The distribution of centroids of forest,reed and carex in the East Dongting Lake wetland layer by layer are close to the lake center,and entroids of these three vegetation types ceaselessly shifted to the lake centre from 1993 to 2006,among which,changes of forest and reed were more remarkable.