| Soil hydrothermal change is the main factor for studying soil.In the context of global change,climate change plays an important role in the process of soil hydrothermal change.Especially in seasonal frozen soil areas,the accumulation and melting of snow,continuous temperature rise and rainfall changes have seriously affected the energy exchange between land an d air.The black soil area of the Songnen Plain is a typical black soil gathering place in the northeast Ch ina.Snow is widely distributed,and soil hydrothermal change will be significantly affected by climate change.Therefore,it is particularly important to explore the changes of soil hydrothermal in this area and its relationship with climate change.The research results can provide support for the prediction of soil spring borer in this area,adjusting the soil hydrothermal balance,and rationally arrange the planting time.In view of this,based on the site data,remote sensing data and simulated assimilation data over the past 30 years in the black soil area of Song nen Plain,this paper discussed the change of temperature,rainfall,snow cover and total precipitation in the black soil area of Songnen Plain by means of correlation analysis,regression analysis,mathematical statistics and contribution rate,and reveals the relationship between soil temperature and humidity an d the change of climate factors.The results show that:?1?The GLDAS simulation data set and weather station data ha ve good consistency on the interannual scale.Therefore,the GLDAS simulation temperature and rainfall data set has good applicability in the study area.Regarding the characteristics of the temperature and rainfall spatial and temporal changes during the snow melting period of the entire study area,the temperature in the study area showed an upward trend in all periods,and the rainfall also showed an upward trend in the late snow melting period.Under the influence of spatial heterogeneity,the annual mean values of temperature and rainfall in the black soil area of Songnen Plain are mainly high in the south and low in the north,which is mainly related to the monsoon climate.It can be seen from the multi-year change trend that the multi-year temperature change shows an upward trend throughout the study area,while rainfall shows a trend of increasing in the south and decreasing in the north.?2?Snow cover is the main climatic factor of seasonal frozen soil,and it is found through analysis and study of snow cover parameters.Over the past years,the first day of snowfall was mainly concentrated in November,and the last day of snowfall was April.Due to the significant impact of global warming,the snow cover days in the black soil area of the Songnen Plain have shown signs of shortening over the years,mainly due to the delay of the first day of snowfall and the shortening of the end of snowfall.It is found that the longest days of snow cover in the northern Nenjiang area of Songnen Plain are 153 days.In the past 32 years,the maximum snow depth in the study area has declined at the rate of 0.53cm·10a-1 Influenced by the spatial heterogeneity,the average distribution of snow depth for many years mainly shows that it increases from south to north in turn,while the trend of change for many years shows that it increases in the southwest and decreases in the northeast.It can be seen from the change of the index of snowfall intensity over many years that the change of snowfall intensity over the years has mainly shown an increasing trend,and its multi-year variation range is mainly 0.09-0.49cm/time.?3?Due to the significant influence of global warming,the mult i-year soil temperature change trend shows an increasing trend,especially in winter.The soil temperature rise rate was relatively fast,and its multi-year trend change range was mainly concentrated between0.3?·10a-1-0.5?·10a-1.Due to the effect of snow cover,there was a clear difference between the temperature and ground temperature during the snow accumulation period,while the temperature and ground temperature during the melting period are close to coincide.During the change of climate factors,air temperature and snow cover are the decisive factors affecting soil temperature.Air temperature and soil temperature have a significant positive correlation,while snow cover and soil temperature have a negative correlation.Affected by spatial heterogeneity,differences in snow depth and geographic location have resulted in asymmetric temperature increase in air temperature and soil temperature.In the later period of snowmelt,the snowmelt water infiltrated the soil and caused the phenomenon of day melting and night freezing,which caused the soil temperature to be affected to a certain extent.?4?Over the past 32 years,the surface soil moisture in the black soil area of the Songnen Plain in the early stage of spring snowmelt generally showed a downward trend,but later showed a downward trend and then an upward trend.For the entire study area,the soil moisture in the pre-snow-melting period showed a downward trend,but the soil moisture in the late-snow-melting period showed the characteristics of rising in the south and falling in the north.Mainly affected by rainfall;the northern part of the study area is affected by the early snowmelt and rainfall,and the late snowmelt is mainly affected by snow and a small amount of rainfall;but because temperature is the main factor affecting soil moisture,therefore,in the entire study area Only in areas where there is less snow and rainfall,the evaporation of temperature will be prominent,otherwise it will be covered by rainfall.The change trend of soil moisture in the early period of snow melting is mainly determined by temperature changes,and the change of snow cover has a certain limiting effect on the process of soil moisture drought.From the calculation resu lts of the contribution rate,it can be seen that the increasing trend of temperature and the decreasing trend of snow cover have doubled the degree of soil moisture drought in the early period of snow melting;while the trend of soil humidity in the later period of snow melting is mainly driven by the trend of rainfall and total precipitation,two factors The positive effect on the soil moisture in the later period of snow melting influences the feedback process of warming and drying,and has a positive ef fect on the soil moisture in the early stage of sowing. |
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