| Purple soil is a specific soil type that are distributed in the tropical and subtropical regions of China.Because its strong physical differentiation,coarse soil particle,weakness in water retention,it results in the poor growth of forest trees.For a long time,the purple soil forest vegetation was seriously destroyed,which leads to the serious soil and water loss in purple soil areas.The improvement of purple soil and the restoration and reconstruction of forest vegetation become the main research topic.This paper takes the four forest types in the purple oil areas including oil-tea forest,masson pine forest at different stages(sapling forest,mid-maturation forest,mature forest),Chinese fir man-made forest(mid-maturation forest,mature forest)and broad-leaved forest as the research objects.It analyzes the physical and chemical properties,enzyme activity,microbial functional diversity and microbial structural diversity of the purple soil in those four types,and explores the correlation among them by mathematical model.It not only reveals the corresponding mechanism of physical and chemical properties,enzyme activity,microbial functional diversity and microbial structure diversity of the purple soil,but also could provide a theoretical basis and technical support for the improvement of the purple soil and the restoration and reconstruction of vegetation in the purple soil area:(1)For the difference of different soil depth,the soil non-capillary porosity,capillary porosity,total porosity,maximum water-holding capacity and natural moisture content of topsoil of four forest types are all higher than that of deeper soil,but soil bulk density is on the contrary.For the soil physical property difference of the same forest type in different stages of forest,the soil bulk densities of oil-tea plantations and masson pine plantations all present "V" change tendency with the increase of age.While soil capillary porosity,total porosity change and maximum water-holding capacity show as reverse "V" change tendency generally.Natural moisture content and non-capillary porosity show as decline tendency.For soil physical property difference of the different forest types in the same stage of forest,soil bulk density shows as masson pine plantations>oil-tea plantations>broad-leaved forest in young forest phase,non-capillary porosity and capillary porosity show as broad-leaved forest>oil-tea plantations>masson pine plantations;in the middle-aged and mature forest phases,non-capillary porosity shows as masson pine>Chinese fir plantation>broad-leaved forest>oil-tea plantations,and maximum water-holding capacity shows as broad-leaved forest>oil-tea plantations>Chinese fir plantation>masson pine plantations.(2)With the deepening of soil layer,both soil pH value and total K contents of four forest types all rise,while the contents of organic matter,total C,total nitrogen,total phosphorus,available potassium,and available phosphorus all present the decline tendency.Under the same forest type,soil available potassium presents "V" change tendency with the increase of forest age,while organic matter,total C,total nitrogen,total phosphorus,available potassium and available phosphorus present reverse "V" tendency.Under different forest types,the contents of soil total K,available potassium,and available phosphorus of different forest age all show as broad-leaved forest>oil-tea plantations>masson pine plantations>Chinese fir plantation;the contents of soil organic matter,total C,and total nitrogen in young phase all show as oil-tea plantations>broad-leaved forest>masson pine plantations,while in the middle-aged and mature forest phases,it shows as oil-tea plantations>masson pine plantations>Chinese fir plantation>broad-leaved forest.(3)The soil sucrose,urease acid phosphatase and catalase of four forest types present decline tendency with the increase of soil depth.For the difference of the same forest type,the sucrose,urease and acid phosphatase of oil-tea plantations and masson pine plantations present reverse "V" change tendency with the increase of age,the catalase of masson pine plantations presents reverse "V" tendency,oil-tea plantations present "V" tendency,while Chinese fir plantation presents rising tendency.For the same forest age,sucrase and catalase show as broad-leaved forest>oil-tea plantations>masson pine plantations in young phase,and urease shows as oil-tea plantations>broad-leaved forest>masson pine plantations;in middle-aged forest phase,urease activity shows as oil-tea plantations>broad-leaved forest>masson pine plantations>Chinese fir plantation,catalase shows as masson pine plantations>broad-leaved forest>oil-tea plantations>Chinese fir plantation,and acid phosphatase shows as oil-tea plantations>masson pine plantations>Chinese fir plantation>broad-leaved forest;in mature phase,urease activity shows as masson pine>broad-leaved forest>oil-tea plantations>Chinese fir plantation,catalase shows as Chinese fir plantation>broad-leaved forest>oil-tea plantations>masson pine plantations,while acid phosphatase shows as oil-tea plantations>masson pine plantations>Chinese fir plantation>broad-leaved forest.The correlation analysis results showed that there is significant correlation between sucrose(P<0.05),urease and acid phosphatase and soil total C,total nitrogen and organic matter,and catalase presents significant correlation with available potassium and available phosphorus(P<0.05).(4)The overall activity of soil microorganism AWCD value of four forest types changes as "S" shape,and presents gradual increase tendency with the increase of forest age.After it is cultivated for 168 hours,AWCD value and Shannon-Wiener diversity index ranked from high to low as oil-tea plantations>broad-leaved forest>masson pine plantations in young phase;in middle-aged forest phase,AWCD value shows as oil-tea plantations>masson pine plantations>broad-leaved forest>Chinese fir plantation,while Shannon-Wiener diversity index and McIntosh index show as oil-tea plantations>masson pine plantations>Chinese fir plantation>broad-leaved forest;in mature phase,AWCD value,Shannon-Wiener diversity index and McIntosh index all show as oil-tea plantations>masson pine plantations>Chinese fir plantation>broad-leaved forest.(5)With the increase of forest age,oil-tea plantations polymer,carbohydrate,phenolic acids,amino acids,amine,carboxylic acids,carbohydrate,amino acid,carboxylic acids,amine,and polymer,carbohydrate,and amino acid of masson pine plantations,and carboxylic acids of Chinese fir plantation present rising tendency.Main contents analysis shows that the use efficiency of polymer,carbohydrate and amino acid in four forest types is the greatest.The correlation analysis shows that Shannon-Winener index presents significant positive correlation with total C(P<0.05),total nitrogen and organic matter,and presents extreme positive correlation with available phosphorus(P<0.05);in the aspect of enzymatic activity,urease presents significant correlation with McIntosh index(P<0.05).(6)There are six soil fungi in four forest types are authenticated,including Ascomycota,Basidiomycota,Chytridiomycota,Glomeromycota and Zygomycota.Among which,fungus category group mainly gives priority to Ascomycota(61.17%-91.20%).Forty seven categories in soil germ of four forest types are authenticated,and the categories with the proportion which is greater than 1%are Acidobacteria,Actinobacteria,Chlorobacteria,Planctomycetes,Verrucomicrobia and AD3.Acidobacteria(28.38%-30.94%)and Proteobacteria(29.49%-35.70%)occupy a greater ratio in four forest types.The correlation analysis results showed that germ chao value presents extreme significant correlation with total K(P<0.05),and Ace value presents significant correlation with soil bulk density(P<0.05);coverage value presents significant correlation with natural moisture content(P<0.05),and presents significant negative correlation with pH value(P<0.05);catalase presents significant negative correlation with simpson index(P<0.05);acid phosphatase presents significant negative correlation with Shannon value(P<0.05),and presents significant positive correlation with coverage value(P<0.05). |
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