Winter Soil Temperature Change And Its Influencing Mechanism In Northeast China In The Past 100 Years（1901-2014）

In the context of global warming,soil temperature changes have become an indisputable fact.As an important agricultural parameter,soil temperature will have an important impact on the sowing and growth of crops.The Northeast region is located in the center of the Northeast Asia region.It also has two major grain production areas—Songnen Plain and Sanjiang Plain.It is the"ballast stone"of my country’s food security.Based on this,this paper uses the land surface model CLM5.0 to simulate the soil temperature in winter in Northeast China from 1901 to 2014,and explore its temporal and spatial variation characteristics and analysis of influencing factors,which has important guiding significance for agricultural production.Research shows:（1）The reliability of the model simulation was verified by using 81meteorological stations in Heilongjiang Province.The sites whose simulated soil temperature values of 0-320cm,10cm,40cm,80cm,160cm,and 320cm were significantly correlated with the observed values at the corresponding locations accounted for the total number of stations.92.59%,96.30%,82.72%,87.65%,93.83%,and 88.89%of the site,the model simulation accuracy is high,and it can reproduce the temporal and spatial evolution characteristics of winter soil temperature in Northeast China in the past 100 years.（2）From the perspective of time series characteristics,the range of soil temperature ranges from 0 to 320cm,10cm,40cm,80cm,160cm,and 320cm in winter in Northeast China over the past century are:-2.0℃～-8.09,-19.12～-6.49℃,-12.92～-4.60℃,-7.79～-1.56℃,-0.63～2.54℃,4.64～6.69℃,the average values are-4.06℃,-10.89℃,-7.35℃,-3.75℃,-0.38℃,5.63℃.The changes were significant（P<0.05）,showing a significant increase trend,and the interannual change trend rates were 0.03℃·10a^-1,0.57℃·10a^-1,0.40℃·10a^-1,0.31℃·10a^-1,0.14℃·10a^-1,0.09℃·10a^-1,further variance results showed that soil temperature increased significantly with the increase of soil depth.In order to further analyze the characteristics of soil temperature change in Northeast China in winter,the past 100years were divided into four climatic states with every 30 years as a climatic state.Increasing soil temperature showed a significant increasing trend.Comparing the performance of soil temperature at the same depth between different climatic states,it can be seen that the soil temperature of 10cm shows significant differences in different climatic states,and the soil temperature of 0-320cm,40cm,80cm,160cm,and 320cm is the second and third climatic states.There were no significant differences among the other climatic states.The results of cluster analysis show that the soil temperature of different climatic states at the same depth is in the first climatic state,and the other climatic states are in the same category.（3）From the perspective of spatial characteristics,the winter soil temperature in Northeast China in the past 100 years has shown obvious latitude variation characteristics,and all showed the spatial distribution characteristics of high in the south and low in the north.The soil temperature of each layer has a clear boundary.The temperature of the shallow soil warmed the fastest,and the soil temperature of each layer showed the fastest rise in Tahe County and Yichun City,Heilongjiang Province.These areas are basically forest-covered areas.In a small part of the area,the soil temperature of each layer showed a significant decreasing trend,and the area where the deep soil temperature decreased significantly was wider.From the perspective of the spatial distribution and Kappa coefficient of soil temperature in different climatic states,the soil temperature of the first climatic state is lower than the soil temperature of the other climatic states,and the soil temperature of the last climatic state has the highest value,indicating that in the four climatic states There are differences in the spatial distribution of soil temperature in the first climate state and the fourth climate state a hundred years ago,and the main difference occurs in the Greater Khingan Mountains in the northern part of the study area.（4）In the past 100 years,the winter temperature in Northeast China conformed to the latitude distribution law,showing a decreasing trend from south to north,and the whole region showed a significant warming trend.From 1981 to 2014,the spatial distribution of the average snow depth in winter in Northeast China was positively correlated with the overall altitude,that is,the average snow depth in the mountainous areas with higher altitudes（Xing’an Mountains and Changbai Mountains）was larger,and the plain areas with lower altitudes（Songnen Plain,The spatial distribution characteristics of small average snow depth in Sanjiang Plain and Liaohe Plain）.The spatial distribution of the correlation between the soil temperature of each layer and each climatic element in Northeast China is very different,and the regional distribution range of the correlation with air temperature reaches a significant level of more than95%,and the whole region is positively correlated.The Greater Xing’an Mountains,the Xiao Xing’an Mountains,the Songnen Plain,the Sanjiang Plain,and the Changbai Mountains showed a positive correlation,and the regions with a significant positive correlation were smaller than the air temperature,indicating that the soil temperature was more affected by the air temperature than the snow cover.