| In the context of climate warming,the global large-scale drought has become an indisputable fact.Heilongjiang Province is close to the center of warming,and drought occurs frequently,especially in spring,which seriously affects grain yield and quality.As the main grain-producing areas,it’s important to analyse spring soil moisture characteristic and influence factor in the main agriculture of Heilongjiang province.Based on the 0-30 cm soil moisture data of 19 agricultural meteorological stations in spring(March to May)from 1983 to 2019 in Heilongjiang Province,this paper analyzed the spatial and temporal variation characteristics of spring soil moisture in two agricultural regions of Heilongjiang Province.Combined with the meteorological data from meteorological stations,the meteorological factors affecting soil moisture were quantitatively analyzed.The conclusion is as follows.(1)Songnen plain spring soil moisture in different soil layers were significantly lower than that of Sanjiang plain,and the soil moisture inter-annual amplitude are larger than that of Sanjiang plain.The soil moisture in the two agricultural areas increased with the depth of soil layer.Soil moisture in the 20-30 cm soil layer in the Songnen Plain showed a significant decreasing trend in spring.The inter-annual variation trend of spring soil moisture in other soil layers in the two agricultural regions was not significant.(2)The soil moisture of different soil layers in different months in spring in Songnen Plain was significantly lower than that in Sanjiang Plain.For different soil layers in the same month,the surface soil moisture in the Songnen Plain and Sanjiang Plain was significantly lower than that in the deep soil moisture.For the same soil layer in different months,the difference of soil moisture is not significant.For the perspective of interannual variation,the soil moisture in the 20-30 cm soil layer in Songnen Plain showed a significant decreasing trend in March and April.The inter-annual variation trend of soil moisture in different soil layers in different months was not significant in the two agricultural regions.(3)In spring,the spatial distribution of soil moisture in different soil layers in the two agricultural regions showed a decreasing trend from east to west.Soil moisture in different soil layers in Songnen Plain was significantly lower than that in Sanjiang Plain in spring.Soil moisture increased with the soil depth in the two agricultural areas.For the spatial variation,the inter-annual variation of soil moisture of more than 50%stations in Songnen Plain showed a decreasing trend at different soil layers in spring.The area with a significant decreasing trend was mainly distributed in Helen-Aokao-Bayan area.Among all the stations,only Wudalianchi showed a significant upward trend.The inter-annual variation of soil moisture in different soil layers in the Sanjiang Plain in spring also showed a decreasing trend.However,the trend of change was not significant,only Fuyuan station showed a significant decreasing trend.(4)The spatial distribution characteristics of soil moisture in different soil layers in different months in spring in the two agricultural regions are consistent.But the ranges of soil moisture are different.In the same month,with the increase of soil depth,soil moisture gradually increased.In the same soil layer,the range of soil moisture decreases and the spatial difference decreases with month.In terms of spatial variation,with the increase of soil depth,the sites with a significant decreasing rate of soil moisture increased,and the decreasing rate increased,in Songnen Plain in the same month.In the same soil layer,the sites with significant soil moisture changes decreased with month.In Sanjiang Plain in the same month,the inter-annual variation characteristics of soil moisture in different soil layers were consistent.In the same soil layer,compared with that in March and April,there were more sites with rising soil moisture in May.(5)Compared with Sanjiang Plain,Songnen Plain has less spring precipitation,less spring precipitation,lower spring earth temperature,longer spring sunshine duration,less precipitation in the previous autumn,less days of yearly snow lying and smaller maximum snow depth.In terms of inter-annual variation,ground temperature and maximum snow depth in the two agricultural regions showed a significant upward trend,the average annual wind speed showed a significant downward trend,the first day of snow cover showed a significantly delayed trend,the spring precipitation in Sanjiang Plain showed a significant upward trend,and the last day of snow cover in Songnen Plain was significantly advanced,while the other meteorological elements showed no significant inter-annual variation.(6)Precipitation in early autumn had a great influence on soil moisture in different soil layers in different months in spring in the two agricultural regions.For the Songnen Plain,days of yearly snow lying and the first day of snow cover can continue to influence the spring soil moisture in the Songnen Plain until May,and can affect the20-30 cm soil layer.As the month progresses,the effect on the shallow soil gradually disappears.The maximum snow depth and the last day of snow cover only affected the surface soil in April.However,temperature,precipitation,sunshine duration and wind speed also have different effects on spring soil moisture in Songnen Plain.Compared with Songnen Plain,the meteorological factors affecting spring soil moisture in Sanjiang Plain are relatively single.In March and April,only the precipitation in the early autumn had a great influence on the spring soil moisture in Sanjiang Plain.As the weather gets warmer in May,the precipitation increases,and the temperature,precipitation and sunshine have a great influence on the soil moisture in Sanjiang Plain.However,snow cover parameters had no significant effect on spring soil moisture in Sanjiang Plain. |
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