Effect Of Forest Conversion On Soil Properties Of Landslide-prone Body

Forest conversion is an important land use type in the middle subtropical zone.Changes in forest types can lead to changes in terrestrial ecosystems and biogeochemical cycling processes,and leading to changes in soil properties.The transformation of natural forests into plantations leads to the breakdown of ecological balance,and the deterioration of soil physical properties and the threat to the ecological environment.Under the background of deteriorating ecological environment,it is of great significance to study the influence of forest conversion on soil properties of landslide-prone bodies for improving human living environment.This study is located in Wufang Forest Farm,Shunchang County,Nanping City,Fujian Province,where landslides occur frequently.On the basis of landslide-prone bodies,broad-leaved natural forests and Chinese fir plantations transformed from them were taken as the research objects.Soil root characteristics,soil basic physical properties,soil structure,soil permeability and soil shear resistance characteristics before and after forest conversion were compared,and the changes of soil properties after forest conversion and the effects of soil interaction on landslide-prone bodies were analyzed.The main results are as follows:(1)RWD,RLD and RSAD of the two forest types decreased with the increase of soil layer.In 0-10 cm soil layer and 10-20 cm soil layer,the decline is the most obvious.After forest conversion,RWD decreased significantly between 0-60 cm soil layers.RWD,RLD and RSAD have different manifestations with the increase of diameter grade.After forest conversion,RDW of the same soil layer > 5mm diameter grade decreased significantly,while RLD and RSAD of the same soil layer did not change significantly.(2)The soil bulk density(BD)of two forest types increased with the increase of soil depth,and the soil bulk density increased after forest conversion.The soil porosity(TP)of the two forest types decreased with the increase of soil depth,and decreased after forest conversion.Silt is the main component of the two types of machinery,but there is no significant change in the mechanical composition after forest conversion.The aggregates MWD and GMD of the two forest types decreased with the increase of soil layer,and the aggregates MWD and GMW of 0-10 cm soil decreased significantly after forest conversion.The basic physical properties and aggregate index of soil become worse after forest conversion.(3)The permeability index of the two forest types decreased with the increase of soil depth.After forest conversion,the permeability of soil decreased.The correlation analysis showed that the soil permeability of natural forest was negatively correlated with soil bulk density,and positively correlated with soil moisture content,pore condition and gravel.After forest conversion,the correlation between soil basic physical properties and permeability of plantation was worse.Soil permeability is linearly correlated with root density,root length density and root surface area.After forest conversion,the correlation between root parameters and permeability decreases.There was a strong correlation between root system and soil permeability in all diameter classes of natural forest.After forest conversion,the correlation decreased,and the root density of each diameter class had no correlation with soil permeability.(4)There is a significant positive linear relationship between soil shear stress and vertical loads in different soil layers of two forest types.The shear water content of the two forest types decreased with the increase of soil depth,and the shear water content of the soil decreased after forest conversion.Soil cohesion decreased significantly after forest conversion.Soil cohesion of BL decreases first and then increases with the increase of soil depth.The soil cohesion of CF increases first,then decreases and then increases with the increase of soil depth.Different soil layers have different factors affecting soil shear strength.After forest conversion,soil root characteristics,water content and mechanical composition are the main factors affecting soil shear strength.