| In the seasonally frozen soil area,due to the influence of the environment,the soil in the freezethaw cycle is accompanied by the migration of water and heat and the exchange and transfer of energy.In order to clarify the actual situation and conduct in-depth research on the soil hydrothermal movement process in the field,this paper considers the atmosphere,the snow cover,and the soil as a composite system to monitor the parameters in the system.This study is based on field field experiments and uses continuous time series data from automatic observations and manual observations to study the variation patterns of soil moisture and heat under different cover patterns,and to screen meteorological factors that have a greater contribution to soil heat and water;Phase transition and migration process,accounting for soil energy budget balance,and then analyzing the effects of energy transfer transformation on spatial scale;using the wavelet transform fractal theory to evaluate the effects of soil water and heat on the complexity of variability,based on which,the establishment of soil The water-heat response relationship function quantitatively describes the transfer relationship of soil water and heat in different time periods;Finally,the CoupModel model was used to simulate the soil water and heat under different covered conditions,which is the water and soil resources in the black soil region of the Songnen Plain.Efficient use and sustainable development of regional ecology and agriculture provide scientific theoretical basis.The main research results are as follows:(1)In the process of freeze-thaw cycle,the soil moisture and temperature gradually decrease with the increase of soil depth in the vertical soil profile.Different snow-stalk co-coverage treatments resulted in a certain difference.In the fast freezing period and the stable freezing period,the variation of soil moisture and temperature will gradually decrease with the increase of snow cover and straw coverage.In the melt season,under the conditions of natural snow cover,the infiltration of snow water leads to the variation range of soil moisture content suddenly increased,and the covering effect of straw modifies the variation characteristics of soil water and heat.With the increase of straw coverage,the variation characteristics of soil water and heat are gradually stable.(2)Frequent energy exchange processes between freeze-thaw soil and the environment are carried out.In the vertical section,with the increase of soil depth,the exchange of soil energy is gradually reduced.Under bare ground conditions,during the rapid freezing period,the proportion of energy at the 10 cm soil layer in the surface layer was 44.28%,which increased by 27.34%,30.27%,and 33.56%,respectively,relative to the specific gravity at the 20,30,and 40 cm soil layers.As the depth of the soil increases,its energy budget decreases gradually.At the same time,with the cover of snow and straw,the difference between the proportion of surface soil energy and the proportion of deep soil is gradually weakening.The differences from big to small are: bare land treatment> natural snowfall> natural snowfall + 5cm straw> Natural snowfall + 10 cm straw.With the increase of soil depth,the trend of changes in soil energy budget weakened.(3)During the soil test period,the balance of soil energy expenditures can be divided into three categories: energy absorption,energy release,and no change.It can be seen that the time nodes of various balancing effects can be known.During the fast-freezing period,the time nodes of energy release are larger,and as the snow cover and the straw coverage increase,the proportion thereof gradually decreases,among which natural snowfall and natural snowfall+ The conditions of 5cm straw and natural snowfall+10cm straw cover were reduced by 9.54%,13.56% and 21.55%,respectively,compared to bare land treatment.In the period of stable freezing,the proportion of time nodes with no change in energy is large.With the increase of snow cover and straw coverage,the proportion gradually increases in turn.During the melting period,the energy node absorbs a large proportion of time,and under the condition of snow and straw covering,its proportion gradually decreases,indicating that the covering treatment inhibits the absorption and expenditure of soil energy to some extent.(4)The balance effect of soil energy results in a periodical change in the net energy time series.The specific analysis shows that on the spatial scale,as the depth of soil increases,the overall net energy sequence of the soil shows a gradually increasing trend.During the fast-freezing period,as the snow cover and straw cover increase,the cycle of soil energy change gradually increases,and during the period of stable freezing,the change trend of its cycle quickly freezes and agrees,and during the melting period,natural The cycle of soil energy change under snowfall treatment conditions suddenly increased,which was significantly higher than that of bare land treatment.With the straw filling and covering process,the cycle of change of the soil energy was reduced to some extent.(5)In the study,it was found that the fitting curve of the difference sequence of each 10 cm soil layer was in line with the Logistic curve.And with this method,the critical layer position of soil activity is defined.From the analysis of the dynamic location of the critical layer of soil water and hot water,it can be seen that with the increase of snow cover and straw coverage,the critical layer of hydrothermal activity is gradually improved,and the definition of the modified method is better,the defined value and measured The error between values is controlled within 5%.(6)In the freezing and thawing process of soil,there is a certain interaction between water and heat.In the period of rapid freezing,the relationship between soil moisture and heat is Gaussian,and the type of the curve conforms to the arc growth trend.In the stable freezing period,with the decrease of the ambient temperature,the change trend of the soil water content is weak,and the composite index of the relationship curve between the two increases,but in the melting period,the relationship between the two is in line with the “S” type.curve.In the vertical section,with the increase of the soil depth,the fitting accuracy of soil water-heat interaction response function is gradually reduced,and the response relationship between the two decreases in turn.The cover of snow cover interferes with the relationship between the two in the melting period to a greater extent,and the filling and covering of straw improves its interaction.(7)Based on the analysis and evaluation,using the CoupModel model to dynamically simulate the soil moisture and temperature during the freeze-thaw cycle,the simulation accuracy of the model is high,and the quantitative quantification of the hydrothermal migration process can be well achieved.simulation.The snow cover has a certain disturbance to the hydrothermal parameters of the soil,and the simulation accuracy is reduced.The cooperative coverage of straw and snow makes the simulation effect of the model improved. |
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