| Taxus maire is The tertiary relic species,is national level protected plant.It has important values of ornamental,timber and medicinal.The cultivation and exploitation of Taxus mairei have caused more and more attentions,and there are increasing amount of research on its medicinal ingredients and cultivation techniques.However,there are still lack of research on its relation with evolution of soil quality and forest.This study used Taxus mairei pure stands,Taxus mairei mixed with deciduous stands,bamboo and hickory forest stands as objects,to study the dynamic changes of forest stand soil properties,soil organic carbon content in soil microbial community structure and soil enzyme activities in different forest types.The aim of this study is to understand the importance of Taxus mairei to the forest soil quality,so that to provide suggestions of scientific management and conservation on Taxus mairei.Our results showed that:1.There was no significant difference in soil pH,total nitrogen,hydrolysis of nitrogen,available phosphorus,potassium,Soil bulk density,porosity,water holding capacity and soil mechanical composition among different dbh sized Taxus mairei forests.Compared to Taxus mairei mixed with deciduous stands,bamboo and hickory forest stands lead to a significant decrease in soil pH,available phosphorous;meanwhile,Soil bulk density and porosity declined,while soil rocky ratio increased;We found significantly higher potassium in bamboo and hickory forests than after Taxus mairei forests(P<0.05).2.We found 14.38~17.55g·kg-1 change of total organic carbon in Taxus mairei forest soils,it was highest in the mature stands,Alkyl C?O-alkyl C?Carboxyl C?Acetal C comprised the largest proportion of organic carbon,whereas,the least proportions were N-alkyl C and Phenolic C,and the ration of aliphatic C / aromatic C reached the maximal value,while the ratio of hydrophilic C / hydrophobic C and aromaticity had the smallest values.There were 30.7% and 28.5% decreased total soil organic carbon after Taxus mairei forests switched to be bamboo and hickory forests;there was slightly change in organic carbon fractions and organic carbon pool Stability,but was not significant.3.All microbial PLFA increased with the growth of forest and reached the peak at mature stage,then decreased in Taxus mairei forest soil.The ratio of soil fungi and bacteria was between 0.34 and 0.41,the ratio of G+ and G-was between 0.96 and 1.52,with no significant difference.We found a significant decrease of microbial PLFA due to the intense management of bamboo and hickory forests,Taxus mairei mixed with deciduous stands > hickory forests > bamboo forest(p<0.05);also ratio of soil fungi and bacteria was significantly increased and the ratio of G+ and G-was significantly decreased,indicated that soil microbial composition was different in different forest types.4.The urea enzymes was highest in matured Taxus mairei forests,saccharase enzymes and acid phosphatase enzymes became more active with the increase of forest age,scavenger enzymes reached its peak activity when forest became mature,then declined.Compared to Taxus mairei forests,bamboo and hickory forests had lower activity of urea enzymes(decreased 63.9% and76.0%),scavenger enzymes(declined 32.3% and39.2%),saccharase enzymes(decreased 7.7%? 45.5%),whereas acid phosphatase enzymes increased(6.0% and21.1%).Evaluation of Forest Soil Quality Using Gray Correlation Degree,Sustainability Index Method and TOPSIS Method,our results showed that the rank of soil quality was: Mature forest> near-mature forest> over-mature forest> middle-aged forest> young forest;Taxus mairei mixed with deciduous stands > Taxus mairei pure stands(class I)> bamboo > hickory forest stands. |
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