Driving Factors Of Ecotope Evolution And The Hydrological And Ecological Response For The Wetlands In Cold Region

Zhalong wetland locates in cool temperate zone, its unique geographic location makes the basin's hydrological and ecological processes couple closely, plays various eco-hydrological functions, such as flood storage against drought, soil erosion control, water purification, biodiversity maintenance, etc. However, in recently years, due to the regional climate change and effect of human activity, the situation of eco-hydrology change particularly, the wetland has degraded seriously. The paper picks up the eco-environmental evolution driving factors of zhalong wetland and eco-hydrological response relation to study, reveal the eco-environmental evolution mechanism of wetland objectively, perfect humble region wetland degeneration and restoration theory of our country. The main research contents as follows:(1)Analyze precipitation, runoff and other climatic and hydrological factors' variation characteristics; reveal humble region wetland climate hydrology variation rule; adopt time series extrapolation to analyze the change period of precipitation and inflow runoff, abstract the wetland hydroperiod; adopt superimposition tendency forecast model to forecast the change tendency of precipitation and inflow runoff within the wetland. The precipitation presents a decrease trend and fluctuates with the period of 21 years, the annual average air temperature shows significant increasing trend, although the annual average evaporation fluctuates significantly, as a whole, it has no evident change trend, and the inflow shows a significant degressive trend and fluctuates with the period of 12 years.(2)Analyze the eco-hydrologic impact of regional climatic changes and human factors based on zhalong wetland eco-hydrological characteristics, calculate the correlation between wetland area and climatic factors with grey correlation method; examine the evident climate and hydrology main factors affecting wetland landscape (surface)area with two kind scales of month and year and its sensibility to environmental factor, separate wetland eco-environment evolution main driving factors. This can get ready for the next research on chapters 4,5 and 6, which aima at the main driving factors' change and wetland eco-hydrologic response to the main driving factor' variation. Zhalong wetland possess spatio-temporal difference and frangibility characteristic, climatic environment and human factor is the wetland dynamic variation's primary effect factor; it has better correlativity between wetland area and climatic factor: it has positive correlation between wetland area and air temperature, and negative correlation with precipitation, grey association coefficient is respectively -0.617,0.467; the monthy maximum air temperature and inflow are the critical factors influencing water surface area of the wetland.(3) Modify the monthy water balance model with two parameters by using correction coefficients of evaporation month by month, establish the inflow simulation model for Zhalong wetland, and study the change of upstream runoff due to climatic change and human activities quantitatively adopted hydrological simulation method. it is shown that the model modified can simulate the wetland inflow very well, that the critical year for inflow series change is 1981, that inflow runoff shows a significant degressive trend, especially in the 1990's, it accounts for 85 per cent of the background value, and that in the 1990's, climate change is the main factors influencing the inflow and the decrement occupies 60% of the total decrement, but in the 1980's, human activity is the main factors influencing the inflow and the decrement occupies 80% of the total decrement.(4)Simulate the inflow runoff and water surface area by using a water cycle system simulation model of the wetland, take water surface area as the typical hydrology state index, discuss the quantitative response of hydrology index to inflow runoff with natural inflow frequency, take reed area, avifauna variety and water quality as ecological environment indexes, discuss the response of ecological environment to hydrology state. the results show that both of the change trends of annual average water surface area and inflow runoff are consistent, that the response of water surface area to inflow runoff is different with different frequency, and that both of the change trends of ecological environment index and water surface area are almost consistent, but the change of ecological environment index lags behind the change of water surface area with different degrees, i.e., water quality, reed area and avifauna variety in order of priority. It is important to note that it is not better for ecological environment when water surface area is bigger, only when water surface area is in the range of 775-880 sq.km, ecological environment is better.(5) From atmosphere-earth lay, discuss the wetland soil circumstance change and its ecological response caused by climate change with seasonal variation; research wetland seasonal frozen ground's distribution characteristic, freeze-thaw rule and eco-hydrologic function; reveal the eco-hydrologic response to climatic change: it has perfect corresponding relation between the wetland soil temperature and vegetation season, in zhalong wetland, moss land's air temperature growing season is from 29, march to 5, November, about 248 days, ground temperature growing season is from 29, may to 15, December, about 200days; zhalong wetland seasonal frozen ground range widely, the soil comes into instable freezing period around 20, October every year, and reach frozen extreme depth until the last ten days of march next year. And finishes melting around 20 may next year; wetland eco-hydrologic process is influenced by seasonal frozen ground and hydrothermal condition to a great extent; the amount of frozen backwater increase by 20-40% is beneficial for plant hibernation and springtime multiply, also is the key factor to promote salinization, swamping and keep ecological equilibrium. Frozen soil prevent seeping, thia can promote wetland's development, seasonal freeze-thaw course has important impact on runoff and groundwater table, the pondage of wetland can be increased by increasing runoff in late spring and early summer, staying precipitation in autumn and winter.