| Wetlands have many important environmental functions and benefits, such as moderating climate, regulating hydrology, degradation pollution, and maintaining geochemical cycling. Wetland change will result in improving or weakening wetland function, and inevitably bring about obvious environmental effects. The west Jilin Province lies in a delicate ecological region. Therefore, as an important ecological unit, wetland change plays a vital role in influencing eco-environment in this area. This paper has many important significance for analyzing the change characteristic and law of damaged eco-system, revealing ecological functions of wetlands, and directing exercises of ecology construction.First, based on remote sensing data, this paper analyzed spatio-temporal dynamic process of wetland change during 1985-2010 by using GIS and RS technologies, and revealed the characteristics of wetland change. Second, combined with long-time series of meteorological and hydrological data, this paper explored the impacts of wetland change on temperature, precipitation and hydrology. Finally, based a scenario analysis method, this paper simulated wetland change during 2010-2020, and evaluated wetland pattern differences from the view of landscape indexes, anti-conferences ability, and eco-system service function value. This paper obtained following conclusions.(1)Wetland pattern changed significantly in the study area during the period of 1985-2010.The total area of wetlands was on a rise in the study area during the period of 1985–2010, with an increment of 24.41%. Natural wetlands(marsh, riparian and lake) gradually decreased because of its transformation into dry field and paddy field, while constructed wetlands(paddy field) increased significantly, mainly from transformation of dry field and wasteland. The lose area of natural wetlands was mainly concentrated along Nen River and Second Songhua River, moreover, neighborhood of Chagan Lake and Yueliang Lake. The increase area of paddy field was mainly located in three major water conservancy projects. A hot spot of wetland change has been permanent in southwestern part of the study area, Qian Gorlos Mongolia Autonomous County, and western part of Songyuan during 1985-2010. A hot spot exited in northwestern part of the study area during 1985-2000, and a hot spot exited in eastern edge of the study area during 2000-2010.(2) Wetland increase and pattern change can moderate regional climate.The change of forest, grassland, and wetland all had contributed to regional climate change during 1985-2010 of the study area. Compared with forest change and grassland change, wetland change plays a more major role in moderating regional climate. Wetland change produces a great impact on local climate, mainly on maximum temperature and precipitation from May to September. The tendency rate of maximum temperature is relevant negatively to the tendency rate of wetland change, while the tendency rate of precipitation is relevant positively to the tendency rate of wetland change. The changes in the tendency rate of maximum temperature and precipitation correspond with wetland change in spatial distribution, respectively. In the mid-eastern part, wetland area dramatically increased, while the maximum temperature increment and precipitation decrement were all lower. In the western and southwestern part, wetland area decreased, while the maximum temperature increment and precipitation decrement were all higher.(3) Marsh change can influence runoff in Tao’er watershed.The results on the analysis on dynamic change of runoff in Tao’er River watershed during 1986-2010 indicated that, in addition to some water conservancy projects, compared with other land-use types, marsh change is most closely to runoff change, followed by the change of saline land, grass land, riparian, and lake. Mean annual runoff in Tao’er River watershed decreased continuously during 1986-2010. The natural reason for the decrease is natural environment change, especially global climate change which resulted in decreasing rainfall and increasing temperature. The humane reason is land-use pattern change, especially marsh change along Tao’er River. Sudden change point of runoff in Tao’er River watershed occurred in 1995, then, the influence of underlying surface change on runoff enhanced, which has become the most important factor leading to the runoff decrease after 2000, rainfall decrease has become the second factor.(4) Wetland landscape pattern of different scenarios is different. In ecological construction scenario, the ecosystem service function value of the study area is the maximum, and anti-interference ability is the strongest.In ecological construction scenario, the ecosystem service function value of all land-use types is 481.04×108 yuan, among which the ecosystem service function value of all wetlands is 262.52×108 yuan, accounting for 54.57% of the total value. Waste treatment, water conservation, and climate moderating are main ecological functions of wetlands, accounting for 77.40% of the total value. External interference on wetlands gradually drops in this scenario. This indicats wetland pattern of ecological construction scenario has stronger ability of anti-interference and self-stabilizing, and can produce the maximum benefits. Implementation of ecological construction is an effective way to increase ecological service function value. |
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