Effects of thinning intensity on soil extracellular enzyme activity and stoichiometric ratio in natural Pinus koraiensis broadleaf forest
[Objective]Studying the changes in soil extracellular enzyme activity and stoichiometry under different thinning intensities in Pinus koraiensis broadleaf forests helps explore the impact of thinning intensity on soil nutrient cycling.This research contributes to the sustainable management and ecological stability of P.koraiensis broadleaf forests.[Method]This study focused on the natural P.koraiensis broadleaf forests in Changbai Mountain forest area of Jilin province,China,subjected to four thinning intensities(CK,0%;LT,14%;MT,27%;HT,41%).Soil nutrient content,soil extracellular enzyme activity,and their stoichiometry were measured and analyzed.Extracellular enzyme vector analysis,correlation analysis,and redundancy analysis(RDA)were used to reveal the impact of thinning intensity on soil extracellular enzyme activity and nutrient limitation in Korean pine broad-leaved forests.[Result]Thinning significantly reduced phosphorus(P)acquisition enzyme activity(ACP)while significantly increasing carbon(C)and nitrogen(N)acquisition enzyme activities(CBH,BG,NAG,LAP).Moreover,with increasing thinning intensity,both C and N acquisition enzymes showed an initial increase followed by a decrease,peaking at moderate thinning levels.Soil EC:P(0.99)and vector length(0.92)were higher under heavy thinning,while EC:N(1.15)and vector angle(57.21°)were higher in the unthinned forest,indicating stronger carbon and phosphorus limitations by soil microbes under heavy thinning and no thinning,respectively.Correlation analysis revealed significant positive relationships(P＜0.001)between soil ammonium nitrogen and C acquisition enzyme activities(CBH,BG),EC:N,EC:P,and vector length,and a significant negative relationship(P＜0.01)with P acquisition enzyme activity(ACP).RDA analysis indicated that soil total nitrogen,ammonium nitrogen,nitrate nitrogen,available phosphorus,and organic matter were important factors regulating soil extracellular enzyme activity with changing thinning intensity.[Conclusion]Appropriate thinning intensity can enhance soil extracellular enzyme activity,alleviate soil microbial nutrient limitations,and promote soil biogeochemical cycling.These findings provide theoretical support for further research on nutrient cycling and resource limitations in natural secondary forests under thinning and offer a scientific basis for the management of P.koraiensis broadleaf forests.
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