Effects Of Rainfall Erosion On Soil Organic Carbon,Soil Water And Soil Temperatureon The Loess Plateau

Water erosion is the main form of erosion in the loess plateau region.Water erosion is one of the important factors affecting the carbon cycle process. If we knowhow the soil environment and the organic carbon composition change after rainning, we will understand the processes of carbon cyclein terrestrial ecosystem more clearly. It has been a hot issue in recent years. The existing research cannot answer the key issues about how erosion influencethe soil carbon cycle. This paper took the hilly loess plateau as the study area. Soil samples were taken from different positon of the slope after a raining season. Soil temperature and humidity were collected by field monitoring. Through the distribution characteristics of soil physical and chemical properties, soil organic carbon composition, soil water and soil heaton sloping land in different organic carbon levels, we wanted to reveal the “pressure-response” relationship between erosion and soil.Basing on the experimental conditions, the main results were as follows:1. Erosion changed the distribution pattern of soil organic carbon(SOC) and soil nitrogen(N)on sloping land. The contents of SOC and N in 0-20 cm soil layersshowed a consistentrule that sedimentary zone>control zone>erosion zone. There was a close relationship between the organic carbon levels and the distribution of SOC or N effected by erosion.The distributions of SOCand N were more susceptible to erosion when the background SOC was at moderate levels.2. The soil microbial biomass carbon(SMBC) in 0-20 cm soil layers had obvious spatial distribution characteristicsin eroded sloping land. The vertical distribution of SMBC showed a decline with depth,The horizontal distribution of SMBC on the sloping land adhere to a consistent rule that sedimentary zone>control zone>erosion zone.A higher variation of the horizontal distribution of SMBC on the sloping land was observed when the background SOC was at moderate levels,suggesting greater sensitivity to erosion at moderate SOC, compared to low or high SOC.3. The contents and the stability of soil water stable aggregate in 0-20 cm soil layerswere very different.With the improvement of SOC levels, the contents of >0.25 mm and >5mm soil water stable aggregate increased, the stability of the soil aggregatewas also enhanced.4. Soil water content exist significant difference on sloping land, and this difference was related to soil organic carbon. The soil water content in the sloping landshowed a clear rule that sedimentary zone>erosion zone, and this rule was more obvious when the background SOC was at moderate levels,suggesting greater sensitivity to erosion at moderate SOC, compared to low or high SOC.Soil water content and soil water retention increased with the increase of organic carbon levels.5. Soiltemperatureexist significant difference on sloping land, the soil temperature in erosion zone is higer than that insedimentary zone. Soil heat capacityincrease with the SOC levels.Rainfall made the soil temperature in 0-10 cm soil layers reduce.With the improvement of SOC levels, the value of reduction decreased gradually.When the sun shines again after rain, the soil temperature of 0-10 cm soil layers needed more time to elevate 1℃with the SOC levels.