The Relation Of The Local Climate Change Characteristics And The Land-atmosphere Interaction Of The Reed Wetland In Liaohe River

The land-atmosphere interaction of the reed wetland through the Sensible Heat,Latent Heat energy exchanges,CO₂,H2 O material exchanges,forming a unique wetland ecosystem and unique climate environment.The water cycle of the earth gas system,carbon cycle and heat transfer are closely related,which have important directive significance to the regional climate,which directly influences and determines the formation and properties of the regional atmospheric boundary layer.Global climate changes have caused changes in the environmental factors of the wetland ecosystem,and the interaction between ground and gas has also changed,affecting the stability of the wetland and the function of regional climate regulation.The climate,hydrology and vegetation status of different wetlands are different,and the environmental factors are interrelated.The Liaohe Delta has the largest coastal reed marsh wetland in our country,but the reed wetland in the Liaohe Delta lacks sufficient understanding of the above problems.The data of the long time series are obviously lagged behind the other highly productive coastal reed wetland ecosystems,and lack of enough material and energy exchange data and the surface between the land and the ground.Environmental datum affects the accuracy of land surface process model and large scale prediction,which restrict China's accurate estimation of "carbon sink" in the climate change scheme.Therefore,it is of profound significance to carry out this research in Liaohe Delta.The results have new cognition on the regional climate change characteristics and the interaction between the ground and gas interaction in reed wetland in Liaohe Delta,and established a calculation method for the exchange of ground and gas between the reed wetland and the reed wetland in the Liaohe Delta,which can simulate the climate change and the global ecosystem for the numerical model.Model,land surface process model and remote sensing retrieval,and greenhouse gas emission reduction plan provide precise regionalization data.In this study,the characteristics and trends of regional climate change in reed wetland were analyzed.By using the eddy correlation method,the earth gas interaction was observed for four years?2012-2015?.The basic physical parameters of the exchange process between reed wetland and atmospheric matter?carbon dioxide flux,water vapor flux?and energy?sensible heat and latent heat?were computed.The changing characteristics of the environmental factors?meteorological,vegetation,hydrology,soil and other factors?were analyzed synchronously,the relationship between the soil and gas interaction and the environmental factors was analyzed.The contribution rate of the environmental factors to the exchange of matter and energy was discovered out,and the statistical model was established,and the carbon budget was simulated with the mechanism model.The main conclusions are as follows:?1?In the past 55 years,the average annual temperature of reed wetland was 9.11?,and the average temperature increased obviously.The tendency rate was 0.31?·10a-1.The average annual relative humidity is 66%,and the trend of increase is not significant.The average annual evaporation was 1540 mm,significantly decreased,and the tendency was 55·10a-1.The mutation time was in 1986.The water supply was sufficient for the year,and the decrease of evaporation was related to the decrease of wind speed.The average annual sunshine hours 2697.6hr decreased,and the tendency rate was-25hr·10a-1.The average annual precipitation is 643.88 mm,and the trend of decreasing precipitation is not obvious.The average annual wind speed was significantly reduced.The average temperature,relative humidity,evaporation and precipitation were the largest in July and August,indicating that the turbulent exchange effect caused by solar radiation on surface heating in July and August was the strongest.Wind speed is influenced by surface roughness and sea land thermal gradient in April and November,with 2 peaks.The number of sunshine hours has 2 peaks in May and September.As the surface of the wetland is covered with water layer,the heat capacity is large.The solar radiation ability is stronger and the solar energy is stored in the daytime.The release of radiation at night can slow down the rate of ground temperature decrease.The difference of day and night difference between the surface temperature and relative humidity is small,and the wind speed is influenced by the roughness of the surface.The diurnal variation of temperature is opposite to the dynamic trend of relative humidity,and there is a humid reverse phenomenon in the near ground.Therefore,the reed wetland has the function of heat preservation,humidity regulation and precipitation.?2?The average concentration of CO₂ in the last 4 years is 380.85±13.25umol·mol-1,which is higher than the global average year by year.The seasonal variation is obvious.In August,the concentration is the lowest and the concentration in December is the highest.During the winter,the CO₂ concentration in the daytime increased obviously,and in the summer there was an obvious decline process.The average annual fixed CO₂ is 2229 g CO₂· m-2,which is 4 times the average carbon sequestration capacity of the global vegetation,and its carbon sequestration capacity is much higher than that of other coastal reed wetlands in China.In the growing season,the absorption of 6⁷ month CO₂ accounted for 70% of the year,and the absorption flux of CO₂ was smaller in the daytime,the maximum at noon,the weak emission in the non growing season,and the largest emission in April and 9¹0 months.The average annual actual evapotranspiration is 597.38±90.25mm·m-2.The larger the yearly precipitation is,the smaller the evapotranspiration.The wetland can replenish water to the atmosphere through evapotranspiration,and evapotranspiration in 5-9 months is 72.58⁸1.42% of the whole year.The water vapor flux is positive during the day,and the range of variation is considerable.The evapotranspiration of the growing season increases with the increase of temperature within one day,and the transpiration and evaporation increase after sunrise.The annual net radiation accumulation is 2868.32±163MJ·m-2,and the net radiation in winter is decreasing year by year.The maximum instantaneous value of net radiation can reach 860 W·m-2 in summer.The annual accumulation of latent heat flux is 1496.89±231.18 MJ·m-2.The average sensible heat year is 550.96±80.94MJ·m-2,and the sensible heat is the smallest in 6-7 months,which makes the temperature and humidity of reed wetland smaller.The average daily variation of latent heat flux does not exceed 320 W W·m-2,and the average daily variation of sensible heat flux does not exceed 160 W W·m-2.From the angle of energy allocation,net radiation has 41⁶3% allocated to latent heat flux,followed by storage flux and sensible heat flux.?3?In the past 4 years,the regional climate of the reed wetland has increased temperature,reduced precipitation,reduced wind speed,reduced relative humidity and reduced sunshine hours.The increase of temperature in winter and spring is obvious,and the average temperature of the 2013-2015 year temperature is higher than that of the years.In addition to the extreme precipitation in 2012,the precipitation in the other three years is lower than the yearly average,mainly because the precipitation in summer is low,and the sunshine hours are lower than the year's average.There is little change in temperature gradient between different levels of soil,and the maximum thickness of frozen soil layer is 70 cm.There is a linear correlation between the thickness of the water layer and the salt content.The growth of the water layer thickness is Ji Weichi at 7.14 cm,and the salt content grows at Ji Weichi at 0.2%.Phragmites australis has strong productivity.The plant energy reaches 272 cm,biomass reaches 2563 g·m-2 and leaf area is 5.1.The soil gas interaction is the result of multi factor interaction.Due to the interaction effect between different factors,the contribution of multiple factors to the interaction of ground gas is studied by partial least squares?PLS?.The maximum contribution rate of the CO₂ revenue and expenditure is water level and soil temperature in the factor.The most significant index to evapotranspiration is the temperature and soil.Soil temperature and the most significant influence on sensible heat are plant height and wind speed.A statistical regression equation for the interaction of earth gas with different factors is established.The fitting model can explain the change of 86.3% CO₂ revenue and expenditure and 89.2% of the evapotranspiration.The simulation results are better,and the interpretation of sensible heat flux is only 28.5%.?4?Using the biogeochemical model of the measured data,the model results have a significant linear correlation with the observed results.The correlation coefficient R2=0.6846,combined with the data of 1984-2013 years' climate and the change of the surface water level,has simulated the carbon sequestration function of the reed wetland in the last 30 years,and the average annual fixed carbon amount is 1502.24g·CO₂·m-2,1994,1997 and 2001 had the largest carbon sequestration,and the change showed an upward trend of volatility,which was an obvious carbon sink.The artificial irrigation measures control the water level and salinity to keep the reed growth to a high level and form a good wetland environment.Therefore,the increase of temperature and precipitation in recent years has not reduced the absorption of CO₂,and there is an increasing trend.