The Analysis For The Feature And The Change Of Wetland Landscape In Sunan County Based On TM/ETM+ Images

As an important and special ecological system on the earth, wetland is one of important living environment of human being in the transition zone between terrestrial ecosystem and aquatic ecosystem. A syetematic research of wetland is important to wetland resources protection and reasonable exploitation, maintaining fundamental eco-process of wetland, improving ecological environment, sustainable development of society and economy.This paper took Sunan Yugur Autonomous county of Gansu Provence as the study area, chosen landsat TM/ETM+ remote-sensing image in 1987, 2000, 2008 and 2013 as major information source, combined with large scale topographic map, land-use data, relevant yearbooks, and used field research and GPS positioning verification to conduct the precision evaluation on wetland data extracted by visual interpretation, maximum-likelihood classification, neural network analysis, support vector machine etc. Among them, visual interpretation is most accurate, whose accuracy is 86.86% and Kappa coefficient is 0.9418, followed by Support Vector Machine, whose accuracy is 77.28% and Kappa coefficient is 0.6983, and maximum-likelihood classification is least accurate, whose accuracy is 58.0% and Kappa coefficient is 0.4872. Wetland type distribution graph of the study area in 1987, 2000, 2008 and 2013 by using visual interpretation shown the spatial distribution feature of wetland resources, and the paper adopted variable quantity, variable speed and rate of variation to have conducted quantitative analysis of the wetland variation from 1987 to 2013; by introducing 10 landscape ecology index such as NP, LPI, LSI and so on, depending on landscape ecology methods, the paper discussed the wetlands landscape features in study area and its variation from the type level and landscape level.Research suggests that there are 9 types of wetlands in study area, and the majortity is natural wetlands. The total wetland area is 1484.95km2 in 2013, accounting for 6.23% of the total land area of Sunan County. During 1987-2013, the area of wetland showed a decreased trend on the whole, with the gross area reducing by 107.72 km2 and reduciton rate 4.14 km2 per year; wetland reduction rate is faster before 2008 than the rate after 2008. Interconversion among wetland types is comparatively obvious; the type whose area is tranferred out most is Permanent River, which mainly changed into flooding wetland and swamp meadow; the type whose area is transferred in most is swamp meadow. Seeing from current situration of landscape characteristics, number of patches within the wetland is comparatively more, with irregular shape, showing heavy degree of separation of wetland landscape and high degree of fragmentation. Seeing from evolution trend, the shape of wetland landscape is complex before 2008, but patch shape of wetland becomes tight and intensive with simple edge. On patch type level and landscape level, landscape and landscape element type have the tendency of fragmentation.