Study On Soil Organic Carbon Content Distribution Characteristics And Its Influencing Factors In Deep Profile Of Loess Plateau

The ecological environment of the Loess Plateau is the key to the healthy operation of the Yellow River.In this region,active research on soil organic carbon is carried out to better understand the content level of soil organic carbon,especially the influencing factors and distribution characteristics of deep soil organic carbon,which can provide scientific basis and theoretical support for improving soil carbon sequestration and soil fertility.It has certain guiding significance to the ecological environment protection in the Loess Plateau region.At the same time,it has certain reference value to alleviate global greenhouse effect and deal with global climate change.This study selected the entire Loess Plateau as study area and collected 1648 soil samples of measured data to a depth of 0-500 cm depth by 67 field drill.Combined with the classical statistical analysis,statistical analysis and regression kriging interpolation method,the loess plateau is studied deeply vertical distribution characteristics of soil organic carbon content and the spatial distribution pattern,and on this basis,discussed the main controlling factors of different depth of soil organic carbon content.The main conclusions are as follows:1.The surface soil organic carbon content(0-20 cm)in Loess Plateau region ranged from 1.05-35.05 g kg-1,and the average value was 6.46 g kg-1,which was relatively low compared with other regions in China.The average organic carbon content in the 0-500 cm soil profile was 2.74 g kg-1,showing a decreasing trend in the vertical direction.In the surface layer,the content of organic carbon was the highest;in the 20-40 cm layer,the content decreased sharply,and such a decline was still obvious in the 40-200 cm soil layer.In the 200-300 cm layer,organic carbon content had a small change and tended to be stable.2.Under three land uses(farmland,forest and grassland),soil organic carbon content on the Loess Plateau showed a decreasing trend in the vertical direction,with a sharp decrease in 0-200 cm depth and a gradual decrease in 200-500 cm depth.Soil organic carbon content under farmland decreased rapidly in 0-200 cm depth,while that of forest and grassland decreased at a similar weak rate.There was a boundary at 180 cm,above which the organic carbon content of farmland,forest and grassland was significantly different(p<0.05).Below this depth,there was no significant difference among the organic carbon contents(p>0.05).The variation of organic carbon content in deep soil tended to be stable under different land uses,so it can be inferred that the organic carbon content in deep soil and its vertical distribution rule are not affected by land use types.3.Soil particle composition(clay,silt and sand content)and average annual minimum temperature were the important factors affecting the vertical distribution of organic carbon in the 0-500 cm profile on the Loess Plateau,and the correlations between soil particle composition and deep soil organic carbon was higher than that of in shallow soil layers.The statistical analysis further showed that soil water content was another important factor,but the influencing depth was 0-200 cm,which was corresponding to the annual infiltration depth of rainfall on the Loess Plateau.Below 200 cm,soil water content had no significant impact on organic carbon content(p>0.05).Land use is considered as an important factor that dominates organic carbon content in surface soil,but has no significant impact in deep soil.4.According to the spatial distribution of soil organic carbon in the entire Loess Plateau.Surface soil organic content was significantly higher than that of other soil layers.In the 0-400 cm layer,there was an area with relatively low soil organic carbon content in the north central area of the Loess Plateau,ordos sandstorm area,and the soil organic carbon content in the area diffusing from the center to the boundary increases significantly.In the 400-500 cm soil layer,the soil organic carbon content in the entire region of the Loess Plateau presented a relatively low level,with no significant difference in the distribution of organic carbon.This study explores the spatial distribution characteristics of soil organic carbon content in 0-500 cm,and explores the relationships between organic carbon content and obtained relevant environmental factors.Understanding this information is helpful for understanding the region spatial variability of soil organic carbon,the organic carbon cycle simulations,and soil nutrients and land use managements,so as to better serve the ecological environment protection on the Loess Plateau.