| Castanopsis tibetana Hance,an evergreen hardwood tree species,which belongs to the family of Fagaceae Castanopsis tibetana is a valuable and economical timber species in subtropical areas.The shape and the crown of the tree are beautiful.The quality of the wood which is reddish is strong and corrosion resistant.It has high protential value in ornamental and economic development.This study focused on the soil quality of natural forests in Longsheng and Ziyuan County and man-made forest in Huangmian,Guangxi Province.In this study,23 soil quality evaluation indexes were selected to discuss the variation of physical and chemical properties and biological properties in the field.Principal component analysis and grey correlation analysis were used to evaluate the soil quality of Castanopsis tibetana Hance timberland in Guangxi.This study provides effective technical support for the scientific afforestation and management mode of the precious tree species.The main conclusions are as follows:1.The research for the soil quality of Castanopsis tibetana Hance timberland(1)According to the descriptive statistics and correlation analysis of soil physical properties in different layers of 0-60cm in Castanopsis tibetana Hance timberland,the pH value of timberland in the study area was acidic.The average value of soil moisture content,carbon-nitrogen ratio,organic carbon,total nitrogen,hydrolyzable nitrogen,available phosphorus and available potassium were decreased with the rising of soil depth,the average value of total K was increasing with the rising of soil depth.The other indicators showed different variations.The variation of other indicators except carbon-nitrogen ratio,Copper and manganese was not affected by soil depth.The values of pH,total K and Fe showed weak variation in the soil layers of the Castanopsis tibetana Hance timberland,which were not sensitive to the soil quality.In the 0?60cm soil layer,soil moisture,organic carbon and nitrogen hydrolysis were positively correlated,total nitrogen,organic carbon and hydrolysis of nitrogen had significant positive correlation Magnesium was positively correlated with copper and zinc,organic carbon and copper were negatively related.(2)According to the descriptive statistics and correlation analysis of soil physical properties in different layers of 0-60cm in Castanopsis tieana Hance timberland,The average value of soil biological indexse were decreased with the rising of soil depth.The variation of fungi,catalase,invertase and protease in different soil layers were the same.The variation of protease was not affected by soil depth.Bacteria,actinomycetes and urease showed strong variation.There was a significant positive correlation between the bacteria and catalase,urease and There was significant positive correlation between fungi and protease in the soil layers of 0-60cm.There was a significant positive correlation between actinomycetes and protease.2.The evaluation for the soil quality of Castanopsis tibetana Hance timberland(1)According to the principal component analysis of 23 indexes of chestnut forest,Norm value was used to select 7 indexes of carbon-nitrogen ratio,hydrolysable nitrogen,available phosphorus,calcium,magnesium,zinc and protease to construct the evaluation index system of soil quality.According to the principal component analysis,the 7 types of forest types in the study area were comprehensively evaluated.The results showed that the cumulative contribution rate of the first 4 principal components was about 89.943%in the 0?60cm soil layer.The quality classification of hook chestnut forest is:A(0.222)>B(0.213)>C(0.170)>D(0.168)>E(0.158)>G(0.148)>F(0.126).The soil quality of A,B and C in natural forest was better than that of man-made forest C,D,F.The control group of grass shrub G ranked higher than pure forest of Castanopsis tibetana Hance F.(2)Based on the principal component analysis and Norm value,the Soil quality evaluation index system was selected.According to the grey relation analysis and a comprehensive evaluation of 7 forest types in the study area,The results showed that A,B and C of natural forest were better than D,E,F,and the result was consistent with principal component analysis.However,the G of the control group was only lower than that of natural forest A,B,C,ranked fourth,and the principal component analysis results were different.The Woodland sort was A(0.86)>B(0.68)>C(0.65)>G(0.63)>D(0.62)>E(0.61)>F(0.60).In the two ecaluation methods of soil quality,the quality of natural forest soil is the best,artificial mixed forest is better,and the pure man-made forest is the lowest.Based on the results of the two methods,the difference of soil quality comprehensive score showed that the difference was not significant,which indicated that the results of the two evaluation methods were reliable. |
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