Distribution Characteristics And Tracing Techniques Using ²¹⁰Pb_ex Applied To Soil Erosion In Alpine Grassland Region

Three-River Headwater Region is located in the Hinterland of Qinghai-Tibet Plateau.Its ecological status is significant,Due to the unique natural and geographical conditions and ecological value,determines the sensitivity and vulnerability of the ecological environment in this area,the change of environment has a great impact on China's climate and environment.Xinghai Basin is located in the core area of Three-River Headwater Region on the upper reaches of the Yellow River.The natural grassland dominated by alpine meadow and alpine grassland is the ecological system in this area.It is of great value to the development of animal husbandry and the maintenance of ecological balance.In recent decades,under the influence of climate warming and human activities,the grassland vegetation of the area is sparse,the fine forge grass is reduced,the yield is decreased;the soil properties are changed,the water holding capacity is reduced,the grassland is degraded gradually,the soil erosion becomes more serious.This seriously restricts the sustainable development of the local economy,society and environment.Therefore,it is significant to study the mechanism of soil erosion in the alpine grassland area,and it is important to understand the change process of the ecological system in the alpine region of China.Taken the Xinghai basin as the research object,soil samples were collected on the basis of field survey,and then,indoor processing,and analysis,Using the ²¹⁰Pb_ex tracing technique,the paper studies vertical and spatial distribution of ²¹⁰Pb_ex,and determined the ²¹⁰Pb_ex background value,and estimated soil erosion rate,the analyzes affect soil erosion factors including climate,vegetation type,cover and so on.The conclusions as follows:1?There are differences in the vertical and spatial distribution of the radionuclide content.The results indicated that the content of ²¹⁰Pb_ex is mainly distributed in the 0-4cm of surface soil.From the surface to the bottom in soil profile,²¹⁰Pb_ex showed exponential decreasing trend.The value of ²¹⁰Pb_ex in the range from 1423.82Bq·m-2 to 7518.71Bq·m-2,Which is alpine meadow>alpine grassland.Using inverse distance weighting?IDW?,the content of ²¹⁰Pb_ex is significantly influenced by human activities.2?At the research area,The author collect seven samples to determine that the background value of ²¹⁰Pb_ex is 4617.76Bq·m-2.Based on the annual average precipitation in Xinghai Basin for fifty-five years,using the background value of ²¹⁰Pb_ex dynamic equilibrium model,the simulation background value of ²¹⁰Pb_ex in this region is 4467.65Bq·m-2.we get that the measured value is very close to the simulation,so this reflects that the reliability and accuracy of selection of the sampling point of reference are also explained.3?Taking into account the actual situation of the study area and the feasibility of the model parameters,the stable state model of Zhang X B's in uncultivated land is selected for ²¹⁰Pb_ex tracing soil erosion study.The results indicate that soil erosion modulus is in range from 114.89t·km-2·a-1 to 528.92 t·km-2·a-1,and the average is 333.33 t·km-2·a-1,soil erosion thickness is in range from0.09mm·a-1 to 0.61 mm·a-1,and the average is 0.31mm·a-1,Which reflects that the soil erosion modulus is alpine meadow>alpine grassland.According to intensity grading standard,it's confirmed that the most of the soil erosion are mild erosion,while only a small proportion of the area is mired erosion.4?Analyzing the relationship between soil erosion modulus and soil nutrients?total N,total P2O5,available nitrogen,available phosphorus and organic matter?,the result show that soil erosion modulus is a significant negative correlation in the level of P<0.05 with total P2O5?available nitrogen and organic matter,respectively.And there is a negative correlation between soil erosion and total N,and available phosphorus,respectively.Total N,organic matter and available nitrogen,organic matter and total N are extremely significant positive correlation.And then,the regression equations are obtained.Spatial distribution of soil nutrients show that total N,available nitrogen,available phosphorus and organic matter content in space gradually is reducing from West to East,and spatial distribution of total P2O5 is similar to the soil erosion changes.