Reconstruction Of Soil Erosion Rates From Exposed Roots In Southeast China

Soil erosion is a normal form of the natural circulation of substances and energy flow,which is also a form of landform evolution.Changting is one of the most eroded areas in China with coarse grained granite weathered red soil,and the soil erosion here is typical of Red soil erosion area in South China.This paper chose the exposed root of Pinus massoniana trees as samples,using dendrogeomorphology method to reconstruct the regional soil erosion rate which the samples recorded.Then we compared the erosion rate with the environmental characteristics of various points(such as slope,vegetation,human activities intensity etc.),and the relationship between environmental factors and soil erosion intensity in this area was discussed in order to explain the reasons for the serious of soil erosion here.Then evaluate the effectiveness of soil and water conservation in Changting from the perspective of dendroecology.The main conclusions of this work are as follows:(1)In this study,we selected 123 exposed roots from 85 Pinus massoniana trees at 6 sites in Changting.We reconstructed the annual soil erosion rates in YFS(20.5 ±9.74mm/yr),YFN(18.2±6.64mm/yr),WSD(16.94 ±8.09mm/yr),YFE(14.01 ±5.94mm/yr),LYK(12.36±5.33mm/yr),SDF(6.53 ± 1.93mm/yr),respectively,ranging from 4.26 to 43.50 mm/yr with an average of 14.14 ± 8.05 mm/yr.(2)The eccentricity ratio of samples in the study area didn't show significant correlativity with soil erosion rate.The eccentricity ratio depends on the duration of erosion,the longer of the erode duration,the larger the eccentricity ratio is.(3)When the root started to expose,the rings began to exhibit a stem-like wood structure with a reduction in earlywood cell lumen area,an obvious earlywood/latewood boundary and an increase in latewood percentage.The distinct reduction of cell lumen area of earlywood tracheids of exposed roots appears to be a good bio-indicator for the first year of exposure due to soil erosion.The occurrence of the significant shifts of root rings may be related to drought conditions because of the reduction of soil cover.(4)A linear regression analysis was conducted to explore the relationship between slopes and erosion rates(P=0.142>0.05;R2=0.018),and the result shows that serious sheet erosion(>14.14 ±8.05 mm/yr)mainly occurs in the slopes of 10°-30° interval.Based on the results of this study,proposals for soil and water conservation programs are proposed.It also turns out that the erosive events registered by exposed roots are closely associated with summer precipitation.