| Oil erosion reduces soil fertility and causes soil nutrient loss and layer becomes thinner,reduces the productivity of forests,has a negative impact on forestry production,but also seriously affected the ecological environment,so that the ecological environment is destroyed,water logging disasters occur frequently,which is not conducive to the sustainable development of forestry and social economy.Therefore,it is very important to study the function of soil and water conservation and improve the ecological environment.A large number of scientific studies have shown that the structure determines the function.The better the stand structure is,the better its function is.The spatial structure is of great significance to the function of soil and water conservation.Optimizing the spatial structure of the stand is an effective way to improve the soil and water conservation function,Therefore,it is of great significance to study the relationship between forest spatial structure and soil and water conservation function.Taking the ecological public welfare forest of Cunninghamia lanceolata in Fushou Forest Farm of Hunan Province as the research object,the spatial structure and soil and water conservation function of the management and control of afforestation stands in 2006 and 1999 were dynamically analyzed.On this basis,the relationship between stand spatial structure and soil and water conservation function was analyzed by multiple regression analysis and path analysis,and the model of relationship between stand spatial structure and soil and water conservation function was established,and the direct and indirect effects of stand spatial structure factors on water and soil conservation function were obtained.Some suggestions were put forward for the improvement of soil and water conservation function of Cunninghamia lanceolata ecological public welfare forest.The main conclusions are as follows:(1)Dynamic analysis of spatial structure of Cunninghamia lanceolata ecological public welfare forest.Five spatial structure indicators of complete mingling index,competition index,open compassion index,stand layer index and uniform angle were selected to analyze the dynamic changes of spatial structure of four forest classification types in 2012 to 2018.The results showed that the complete mingling index of managed stand in 2006,control stand in 2006,managed stand in 1999 and control stand in 1999 increased by 111.76%,53.33%,375%and 22.22%respectively in 2018;The competition index increased by 16.99%,16.61%,0.52%and 10.70%.The open compassion index decreased by 20.48%?13.09%?57.89%and 22.64%,respectively.The stand layer index increased by 63.16%,29.71%,50.00%,28.00%respectively.The uniform angle decreased by 20.34%,8.33%,23.21%,6.89%respectively.(2)Dynamic analysis and evaluation of soil and water conservation function of Cunninghamia lanceolata ecological public welfare forest.Delphi method was used to select 14 indicators of water conservation function and soil conservation function to dynamically analyze the soil and water conservation function of four forests and to evaluate it by analytic hierarchy process.The results showed that the soil water content of the four stands increased by 19.81%,1.79%,50.44%and 21.34%,the soil porosity increased by 3.01%,2.49%,11.20%and 0.45%,and the soil bulk density decreased by 19.42%,11.64%,20.89%and 10.37%,respectively in 2018.The soil structure of the managed plots was improved obviously.The biomass of shrub and grass increased by 10.28%,1.89%,64.13%and 1.11%respectively.The maximum water holding capacity of shrub and grass increased by 43.69%,6.55%,112.94%and 4.65%respectively.The maximum water hold-up of shrub and grass increased by 30.18%,4.58%,29.89%and 3.69%respectively.The biomass of litter increased by 13.20%,8.58%,28.65%and 18.79%,respectively.The maximum water holding capacity of litter increased by 26.36%,11.06%,48.72%and 20.15%,and the maximum water hold-up of of litter increased by 11.61%,2.24%,15.60%and 1.15%,respectively.Soil organic matter content increased by 38.29%,17.73%,32.54%and 19.20%,soil total N content increased by 103.74%,75.22%,84.34%and 64.86%,soil total K content increased by 29.46%,10.43%,36.88%and 17.51%,respectively.Soil total P content increased by 69.09%,57.14%,97.78%and 49.02%respectively.Soil pH increased by 11.81%,9.72%,11.28%and 9.73%,respectively.This paper evaluates the soil and water conservation function of Cunninghamia lanceolata ecological public welfare forest in Fushou Forest Farm by using analytic hierarchy process,and establishes the function model of soil and water conservation,the model is as fellows:A=0.0583Y1+0.1021Y2+0.1771Y3+0.0191Y4+0.0337Ys+0.0131Y6+0.0244Y7+0.055Y8+0.0173Y9+0.2269Y10+0.0861Y11+0.0543Y12+0.01086Y13+0.0240Y14In the formula,A is the quantitative index of soil and water conservation function,Y1 is the soil water content,Y2 is the soil porosity,Y3 is the soil bulk density,Y4 is the biomass of shrub and grass,Y5 is the maximum water holding capacity of shrub and grass,Y6 is the maximum water hold-up of shrub and grass,Y7 is the biomass of litter,Y8 is the maximum water holding capacity of litter,Y9 is the maximum water hold-up of of litter,Y10 is the soil organic matter content,Y11 is the soil total N content,Y12 is the soil 1 total K content,Y13 is soil total P content,Y14 is soil pH.Through comprehensive scoring method,the score of soil and water conservation function of two kinds of management stands is higher than that of control stands,and the score of soil and water conservation function of management stands in 1999 is higher than that of management stands in 2006.(3)The study about the relationship between stand spatial structure and soil and water conservation function.In this paper,multiple regression analysis and path analysis were used to study the effect of stand spatial structure on soil and water conservation function and its relationship model.The results showed that stand layer index and complete mingling index had a strong direct impact on soil water holding capacity and soil bulk density,and the spatial structure factor that had the greatest direct impact on soil porosity was the complete mingling index.The direct influence degree on shrub and grass biomass and the maximum water holding capacity of shrub-grass is open compassion index;Forest layer index is the most important spatial structure factor that directly affects the maximum water hold-up of shrub and grass.The forest layer index is the most important spatial structure factor that directly affects the water conservation function of litter layer.The direct influence on soil organic matter content is complete mingling index;and the direct influence degree on soil total N content is competition index;the most obvious factors affecting soil total K content are complete mingling index and open compassion index.The complete mingling index have greater impact on total P content.The most obvious structural factors affecting soil pH directly are the complete mingling index and competition index.Based on the multiple regression analysis and soil and water conservation function evaluation,the spatial structure and soil and water conservation function model of Cunninghamia lanceolata ecological public welfare forest in Fushou Forest Farm were obtained,the model is as fellows:A=4.659X1+0.105X2+1.721X3+10.377X4-7.242X5+15.382In the formula,A is the quantitative index of soil and water conservation function,X1 is the total mixing degree,X2 is the competition index,X3 is the open ratio number,X4 is the forest layer index,X5 is the angle scale.Through the research,it is found that the spatial structure of stand plays an important role in the function of water and soil conservation,Therefore,the spatial structure of stand is optimized.Replenishing local broad-leaved tree species under forests,is conducive to improving the soil and water conservation function of forests and increasing the stability of forests,so as to ensure the healthy growth of forests. |
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