香椿中龄林间伐对林分生长和土壤酶活性及其化学计量比的影响OA

To analyze post-thinning soil nutrient demand dynamics and propose scientific thinning and man-agement strategies for middle-aged Toona sinensis plantations,this study investigated a 7-year-old planta-tion(density:1 419 stems/hm2)in Pengshan District,Meishan City,Sichuan Province.Three thinning in-tensities(1/4,1/3,and 1/2)were implemented with unthinned stands as control.Five years post-thinning(12-year-old stands),we analyzed stand growth,soil chemical nutrients,enzyme activities,and their stoi-chiometric ratios.Key findings include:1)Thinned stands exhibited significantly greater growth than con-trols,with 1/2 intensity stands showing 1.17 times larger mean DBH and 1.40 times higher individual vol-ume compared to controls.2)Soil C,N,P,and K concentrations were lower in the 1/3 thinning treatment but partially recovered under the 1/2 thinning intensity.3)Correlation analyses revealed significant posi-tive relationships between β-glucosidase(βG),β-glucuronidase(βLU),and N-acetyl-β-D-glucosaminidase(NAG)activities and their substrate(soil organic carbon,SOC).Conversely,leucine aminopeptidase(LAP)and acid phosphatase(ACP)activities showed negative correlations with their target nutrients(N and P,respectively).4)Redundancy analysis(RDA)identified SOC,total nitrogen(TN),alkali-hydrolyza-ble nitrogen(AN),and total phosphorus(TP)as key factors influencing soil enzyme activities.5)Enzyme stoichiometry indicated N limitation in soil microbial communities across all stands and the 1/2 thinning in-tensity alleviated microbial C and N limitations.In conclusion,thinning enhanced stand growth in middle-aged T.sinensis plantations,with high-intensity thinning(1/2 intensity,retained density:825 trees/hm2)particularly suitable for large-diameter timber cultivation and sustainable forest management through miti-gation of soil microbial nutrient limitations.