鄱阳湖湿地水位变化的景观响应

根据《湿地公约》和《全国湿地资源调查技术规程(试行)》关于湿地内涵和界定条件,利用现代遥感技术和地理信息技术,提取鄱阳湖湿地面积为3886km²。在此基础上,利用多时段遥感影像,分析了湿地在相似水位条件和不同水位条件下的景观变化。结果表明,在相似水位条件下,鄱阳湖湿地景观变化主要表现为居民地和裸地面积增加,水域面积变化不明显;在不同水位条件下,鄱阳湖湿地景观变化比较显著。景观变化驱动力分析表明,湿地水位变化是湿地景观变化的主要因素。

Landscape responses to changes in water levels at Poyang Lake wetlands

Poyang Lake is the largest freshwater lake in China and one of the world's sites recognized in the RAMSAR Convention on Wetlands. The area is rich in biodiversity, supporting numerous species of invertebrates, fish, birds and mammals including the White Crane (Grus leucogeranus), Cygnet (Cygnus columbianus), Chinese sturgeon (Acipenser sinensis), and Cowfish (neophocaena phocaenoides). The wetlands provide an important range of ecosystem services; and their protection is an important concern both domestically and abroad. Poyang Lake is subject to seasonal fluctuations, with changes in water levels apparent in seasonal, yearly and multi-year patterns. However, the lake is shallow, and the pronounced changes in water levels could lead to the large alterations in the wetlands landscape. This article focuses on the wetlands boundary and landscape changes at Poyang Lake. In order to compare changes in the wetlands landscape under different conditions, water levels were selected for observation in periods of flooding and lack of rainfall. The wetlands boundary was analyzed based on the "RAMSAR Convention" and "National technical specification for wetland resources survey (interim)" using remote sensing (RS) and GIS tools. The area of Poyang Lake wetlands is 3886km². Changes in landscape spatial pattern were analyzed for both equivalent and different based on remote sensing images over multiple time periods from 1980s to 2000s. The observed periods when water levels were similar at approximately 11m occurred from November to February when a number of White Cranes wintered in Poyang Lake. The landscape matrixes displayed similar attributes and the changes of area in the water body were not substantial. Residential area and bare lands area clearly increased in these periods of equivalent water levels. However, changes of landscape index and of area of landscape types in the wetlands were quite obvious when water levels differed from high water levels to low water levels. The area of water body decreased markedly and the area of tide flat occupied the larger proportion of overall area when water levels were low. The area of water was 3617km^2. on July 8^th 1998 when the water levels were 21.55m, there was no tide flat when the water levels were high. However, the area of water was only 1008km² on February 12^th 2009 when the water levels were 7.66m; and the tide flat occupied a more extensive area of 1153km². According to the analysis of driving forces, seasonal changes in water levels were the main influences on changes in the wetlands landscape.