Spatiotemporal pattern of bird habitats in the Poyang Lake based on Landsat images

Abstract

The Poyang Lake is the largest freshwater lake in China and possesses unique wetland and plentiful biological resources. Because of the dual influence of the Five Rivers and Yangtze River, the water level of Poyang Lake changes seasonally, which has important influence on the local ecosystem. A better knowledge of the spatiotemporal pattern of water body and bird habitats is important for bird diversity conservation and wetland management. In this study, we collected six Landsat images in both winter and summer seasons from 1995 to 2009. These images were processed in both ERDAS Imagine 9.1 and ArcGIS 9.3 by image registration, geometric rectification and classification based on image characteristics and field survey data. The bird habitats in Poyang Lake wetland were classified into six types as shoal water, middle-depth water, deep water, grassland, sand land and mudflat. The results showed: (1) In winter seasons, grassland, mudflat and shoal water were the three main bird habitats in winter (totally around 70 %); water body area increased 13.6 % from 1995 to 1999 and then decreased 11.8 % from 1999 to 2007, and the mudflat decreased all the time from 1995 to 2007. (2) In summer seasons, water area occupied more than 60 % of the whole area; due to high water level, most plants were submerged and not suitable for bird feeding; shoal water area and grasslands were the two main bird habitats in summer. Compared with changes in summer seasons, all bird habitats changed obviously in winter seasons. Based on our research, we suggests that it is important to monitor the change in water level, area of water body, area of grassland and mudflat in future research by incorporating related precipitation data, water station record, multispectral and multi-temporal remote sensing images in the Poyang Lake since these habitats are key for migrating birds.