Effect of thinning restoration on enzyme activity and enzyme stoichiometry in the topsoil of oak-pine mixed forest
[Objective]This study,with an investigation of the effects of different recovery periods after thinning on soil physical-chemical proprieties and extracellular enzyme activities in oak-pine mixed forests in the Qinling Mountains,is aimed to better understand the nutrient cycling processes under thinning treatments,providing basis for developing programs of sustainable forest management and exploring better ecological restoration measures.[Method]First,pace-for-time substitution was employed to explore the effects of thinning restoration process(5 and 13 years,no thinning as the control)on soil physical-chemical proprieties and enzyme activity changes in the surface layer at 0-10 cm depth.Then the enzyme stoichiometric ratios and enzyme vectors were calculated for each treatment.[Result](1)The total phosphorus,microbial biomass carbon,and microbial biomass nitrogen contents in the soil increased significantly,whereas the inorganic nitrogen content decreased in the 13-year restoration(P＜0.05)and the soil pH increased in the 5-year and 13-year restorations;following a 13-year restoration,the soil organic carbon content progressively recovered to pre-thinning levels after declining dramatically in the 5-year restoration(P＜0.05).(2)Thinning significantly increased the activity of β-glucosidase(BG),while decreasing the activities of β-xylosidase(BX),nitrogen acquiring enzyme(NAG+LAP),and acid phosphatase(AcP)(P＜0.05);after the 13-year restoration,the activities of phenol oxidase(POX)and peroxidase(PER)showed a decreasing tendency during the initial stage of thinning(5 years treatment)and then reverted to pre-thinning values.(3)In the 13-year restoration,thinning significantly increased the soil enzyme carbon-nitrogen ratio(EC/N),soil enzyme carbon-phosphorus ratio(EC/P)and vector length value(P＜0.05)whereas the EC/P and soil enzyme nitrogen-phosphorus ratio(EN/P)increased significantly and the vector angle value decreased in the 5-year restoration(P＜0.05).[Conclusion]Soil nutrients,organic carbon,and oxidase activities showed a recovery trend with the thinning recovery stage with the soil pH being a key factor affecting soil enzyme activity and the change of enzyme vectors.Thinning decreases the phosphorus limitations of soil microorganisms during the initial stage of recovery,but it has little effect on the phosphorus and carbon limitation in the later stage of recovery.[Ch,3 fig.4 tab.41 ref.]
万方数据
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