Study On The Influence Of Litter On Nitrogen Loss From Surface And Subsurface Runoff On Sloping Land

As an important part of terrestrial ecosystem,litter is an important impact factor of hydrology,ecology,soil and environment in mountainous areas.In recent years,with the restoration and reconstruction of vegetation,the area of forest cover in China has been continuously increasing,and a large amount of litter has been accumulated on the surface.The impact of litter on forest hydrological cycle and biogeochemical cycle can not be ignored.At present,the research on litter mainly focuses on litter decomposition,the influence of litter on soil nutrients and microorganisms,and the influence of litter on sediment production,while the study on litter mulching on soil nitrogen loss is relatively lacking.Based on the process of water cycle and nitrogen cycle in forest ecosystem,this study carried out litter leaching test and rainfall runoff production test in bamboo forest and arbor forest.Automatic weather station was set outside the runoff plot,and soil moisture monitoring system,runoff monitoring system and runoff collection system were set inside the runoff plot to obtain relevant data.Based on meteorological data,soil water content,surface runoff and soil runoff,and nitrogen content in runoff obtained simultaneously from 2019 to 2020,the nitrogen change rules in the process of forest rain,litter leaching solution,surface runoff and soil runoff were analyzed,and the nitrogen loss fluxes in the field covered with or without litter under natural rainfall conditions were estimated,and clarified the effect of litter on the nitrogen loss amount and loss path of slope land.The main work and research achievements are as follows:(1)Litter leaching can increase the nitrogen content in rainfall,but the phenomenon of interception of nitrogen by litter appears in the late stage of continuous rainfall.Litter cover increased the content of total nitrogen(TN)in 0-30 cm depth soil,especially in 0-10 cm depth soil.(2)Litter has the function of delaying runoff and reducing runoff peak.Litter can significantly reduce the surface runoff,in which bamboo litter can reduce the surface runoff by 34.8% to 100%(except for heavy rain),and arbor litter can hardly produce surface runoff.In more than half of the rainfall events,bamboo litter increased the interflow.In 21.7% of the rainfall events,litter in arbor forest increased the interflow,but the increase was small.Litter can increase the yield under heavy rainstorm conditions.(3)Under light and moderate rain conditions,bamboo litter increased TN concentration of surface runoff and soil flow,while under heavy rain and rainstorm conditions,it decreased TN concentration of runoff.Arbor litter increased TN concentration in surface runoff and soil flow in most rainfall events.The nitrogen concentration of surface runoff without litter has a rapid response to rainfall intensity,and the TN concentration of surface runoff also has a peak after the rainfall peak,while the TN concentration of surface runoff with litter coverage gradually decreases and tends to be stable with the runoff process.(4)In the process of nitrogen loss,the effect of litter on reducing runoff yield was stronger than that on increasing nitrogen concentration in runoff,which ultimately reduced the amount of nitrogen loss.However,under the condition of heavy rain,the amount of nitrogen loss increased because the runoff of the slope land covered by litter was much larger than that of the slope land without litter.