Research On Soil Effects Under Different Afforestation Models In The Limestone Mountain Of North Jiangsu Province

In this study, five kinds of afforestation model i.e.Platycladus orientalis,Cotinus coggygriaScop and Koelreuteria paniculata mixed forest,Platycladus orientalis and Firmiana simplexmixed forest,Platycladus orientalis and Liquidambar formosana mixed forest,Platycladusorientalis forest,Platycladus orientalis and Ligustrum compactum mixed forest are selected asobjects in the Limestone mountain of north Jiangsu Province.I studied the contents andcharacteritiscs of seasonal variation of soil active organic carbon and soil enzyme,the soilnutrient status,the correlation among soil active organic carbon,soil enzyme activities and soilnutrients.Principal component analysis was used to evaluate the soil fertility under differentafforestation models.Through to research the soil effects under different afforestationmoldels,that could provide the scientific basis for the best choice of afforestation models in thestudy area.The results showed that:(1)The content of soil total organic carbon under the mixed forests were all higher than thepure forest,and three kinds of soil active organic carbon had the same results.The variationtendency of TOC under five kinds of afforestation model was: CF>CN>CQ>CHL>C; thevariation tendency of SMBC under five kinds of afforestation model was:CN>CQ>CF>CHL>C;the variation tendency of ROC under five kinds of afforestation modelwas: CQ>CF>CN>CHL>C; the variation tendency of WSOC under five kinds of afforestationmodel was: CF>CQ>CN>CHL>C.(2) The contents of SMBC,WSOC and ROC with seasonal variation showed significantdifferences.SMBC has same rule of seasonal variation under five kinds of afforestation model,the variation tendency of SMBC was: the SMBC content was higher in spring and summer,butlower in autumn and winter. WSOC has same rule of seasonal variation under five kinds ofafforestation model, the variation tendency of WSOC was: the content was higher inautumn,and lower in summer and winter, the conent of spring was in the middle.The variationtendency of ROC was: the content was higher in summer and lower in spring,autumn andwinter.(3)Soil enzyme activities had significant differences under different afforestation models.The variation tendency of catalase activity under five kinds of afforestation model was:CF>CQ>C>CN>CHL; the variation tendency of urease activity under five kinds ofafforestation model was: CQ>CHL>CF>C>CN; the variation tendency of invertase activityunder five kinds of afforestation model was: CQ>CF>CN>CHL>C; the variation tendency ofphosphatas activity was: CN>CF>C>CQ>CHL.(4) Soil enzyme activities had significant differences changed with seasons, every kind ofsoil enzyme has differernt rule of seasonal variation under different afforestation modles. Catalase activity and phosphatas activity had same rules with the seasons change under fiveafforestation modles, the variation tendency of catalase activity and phosphatas activity underfive kinds of afforestation model were: enzyme activity was higher in autumn and winter,andlower in spring and summer. Invertase activity had same rule of seasonal variation under fivekinds of afforestation model,and the variation tendency of invertase activity was: enzymeactivity was highest in winter and lowest in spring and autumn, the enzyme activity of summerwas in middle.Urease activity under CHL,CQ and C afforestation models was all highest inautumn; urease activity under CF model was highest in winter; urease activity under CN modelwas highest in summer.(5)Four kinds of mixed forest improved the physical and chemical characteristics of soilstronger than Platycladus orientalis pure forest. According to the results of principal componentanalysis,the comprehensive evaluation of soil fertility came to a conclusion that:CF>CQ>CN>C>CHL. Platycladus orientalis and Liquidambar formosana mixed forestshowed the strongest soil fertility.(6) Phosphatas and urease activity is significantly positively correlated with invertaseactivity.There is correlation between soil enzyme activitiy and soil nutrient, so enzyme activitycould be used as an evaluation index of soil fertility. The correlation between TOC and soilactive organic carbon or among fractions of soil active organic carbon reached significant orextremely significant level.