Effects Of Stand Density And Litter On Soil And Water Conservation Function Of Cryptomeria Japonica

In order to reveal the effects of stand density and litter on the soil and water conservation function of Cryptomeria japonica in Lushan Nature Reserve,field investigation and indoor analysis were used to study the effects of low density(378?555plants/hm~2),medium density(588?622plants/hm~2)and litter on Soil and water conservation function of Cryptomeria japonica in Lushan Nature Reserve Litter nutrient content and soil water conservation capacity of Cryptomeria japonica forests with high density(1011-1444 plants/hm~2),The soil and water conservation function of Cryptomeria japonica with three stand densities was evaluated,The results show that:(1)The soil and water conservation capacity of the high density Cryptomeria japonica is the best.With the increase of soil depth,the soil and water conservation capacity of the density stands decreases gradually.Among the three densities of Cryptomeria japonica,the soil bulk density of high density Cryptomeria japonica was the lowest,which was0.65g/cm~3.The capillary porosity,non capillary porosity,total porosity,maximum water holding capacity,minimum water holding capacity and capillary water holding capacity all showed low density<medium density<high density,and there were significant differences with the other two forest structures(P<0.05).In different soil layers,the soil bulk density increased with the increase of soil depth,while the maximum water capacity,minimum water capacity and capillary water capacity decreased with the increase of soil depth.(2)Stand density and soil layer change had significant effects on soil water conservation capacity(P<0.05),among which stand density change had extremely significant effects on soil bulk density,maximum water holding capacity,minimum water holding capacity,capillary water holding capacity and total porosity(P<0.01),had significant effects on capillary porosity(P<0.05),and soil layer change had significant effects on soil bulk density(P<0.05).(3)The water stable aggregate content of Cryptomeria japonica stands with density>2mm accounted for the highest proportion,ranging from 37.65%?49.27%.The changes of stand density,soil layer,stand density and soil layer interaction had significant effects on the water stable aggregate content of Cryptomeria fortunei(P<0.05).(4)The soil mean mass diameter(MWD)and geometric mean diameter(GMD)of Cryptomeria japonica with three stand densities showed the highest value of high density and the lowest value of high density of fractal dimension.With the increase of soil layer,both MWD and GMD showed a decreasing trend,but the fractal dimension showed an increasing trend.(5)The litter yield and total phosphorus of high density Cryptomeria japonica were the highest,while the organic carbon and total nitrogen were the lowest;There were significant differences in C/P between the middle density and the other two stands(P<0.05),but no significant differences in N/P among the three stands.(6)Correlation analysis between litter and soil and water conservation showed that organic carbon,total nitrogen,total phosphorus and C/N had significant correlation with soil and water conservation function.There was no significant correlation between litter yield,N/P and soil and water conservation indexes.Organic carbon content had significant positive correlation with capillary pore,total pore and geometric mean diameter(P<0.05),but had significant negative correlation with fractal dimension(P<0.05),and total nitrogen content had extremely significant negative correlation with fractal dimension(P<0.05).The total phosphorus content of litter was positively correlated with soil bulk density(P<0.05),and negatively correlated with maximum water holding capacity,minimum water holding capacity and capillary water holding capacity(P<0.05).The stoichiometric C/N of litter was negatively correlated with capillary pore(P<0.01),negatively correlated with total pore(P<0.05),positively correlated with geometric mean diameter(P<0.05),and the correlation coefficient was 0.446,while C/P was negatively correlated with fractal dimension(P<0.05).(7)The comprehensive analysis of soil and water conservation function showed that the soil and water conservation function of high density Cryptomeria japonica was the strongest,followed by low density forest,and the soil and water conservation ability of medium density forest was the weakest.Among them,the first principal component includes soil bulk density,maximum water holding capacity,capillary water holding capacity and total porosity,the second principal component includes average mass diameter and geometric mean diameter,and the third principal component includes fractal dimension.In conclusion,stand density had significant effects on soil bulk density,maximum water holding capacity,minimum water holding capacity,capillary water holding capacity,total porosity and capillary porosity.Litter organic carbon,total nitrogen,total phosphorus and C/N had significant correlation with soil and water conservation function.Among the three stand densities,high density(1011?1444 plants/hm~2)showed good soil and water conservation function.