Study On Runoff And Sediment Yield Process Of The Cross Ridge And Longitudinal Ridge Slope Under Natural Rainfall

Seasonal freezing and thawing is the most common natural phenomenon in the northeast of China.It has direct or indirect effects on soil physical and chemical properties and biological characteristics,and is an important factor affecting the content of soil organic carbon and its components.In this study,the topsoil of different land use types was used as the research object to analyze the content of soil organic carbon and its components,and to clarify the trends and correlations of total organic carbon,soluble organic carbon and microbial biomass carbon in soils during freeze-thaw period.To provide a theoretical basis for further investigation of soil carbon pool changes and organic carbon cycle mechanisms in the region.The main conclusions are as follows:(1)The contents of soil TOC,DOC and MBC in different land use types were all greater than that of farmland and bare land in forest land and grassland.The contents of TOC and DOC in soil were woodland> grassland> cultivated land> bare land,and soil MBC content was grassland> woodland> Cultivated land> Bare ground;Soil TOC of different land use types showed significant positive correlation with DOC and MBC(P<0.05),and the correlation coefficient was above 0.8,indicating that the higher soil total organic carbon content,the higher the content of soil DOC and MBC..(2)The total organic carbon content and the degree of variation in 0-10 cm soil layer were significantly higher than those in the 10-20 cm soil layer during the entire period of seasonal freezing and thawing,but there was no significant difference between soil DOC and MBC(P>0.05);Soil organic carbon content in layer depth was positively correlated with soil DOC and MBC content(P<0.05),and the correlation coefficient was above 0.6.(3)The content of total organic carbon in different slopes was below the slope> in the middle of slope> above the slope,and the soil MBC content was below the slope> over the slope> in the slope;the contents of soil DOC and MBC decreased first and then increased at different slope positions.Large;There is a significant positive correlation between total organic carbon(SOCC)content and soil DOC and MBC content in different slopes(P<0.05),and the correlation coefficient is above 0.6;soil total organic carbon content shows weak variability on the slope,soil DOC and The MBC content is moderately variable in the slope and below the slope.(4)During the whole freeze-thaw period,the content of total organic carbon in the soil showed no significant change,indicating that the seasonal freezing and thawing had a threshold on the total organic carbon in the soil.With the change of the freeze-thaw period,the total organic carbon in the soil gradually decreased.Small,the difference graduallydecreases.Seasonal freezing and thawing had a significant effect on soil DOC and MBC content in different soil layers.There was a significant positive correlation between soil organic carbon and soil DOC and MBC in different soil depths(P<0.05).The soil DOC and MBC content in different depths of soil had a significant effect.