施氮对毛竹林土壤胞外酶活性的影响

[Objective]This study focuses on the economically and ecologically significant bamboo species,Phyllostach ys edulis,against the backdrop of increasing global nitrogen deposition.We systematically investigate the effects of nitroge n fertilization on soil extracellular enzyme activities related to carbon,nitrogen,and phosphorus in bamboo forests,aiming to elucidate the critical role of soil extracellular enzymes in nutrient cycling and further deepen our understanding of the c omprehensive effects of nitrogen application on soil nutrient dynamics.[Methods]A randomized block design was employ ed,comprising four nitrogen treatment levels(0,242,484,726 kg N·ha⁻¹·yr⁻¹).The experiment commenced in October 2021.Each treatment was replicated in three 15m×15m plots,with a 5m buffer zone between plots.Urea(N 46.4％)was applied as the nitrogen source,alongside phosphorus and potassium fertilizers(calcium superphosphate and potassium chlori de).Soil samples were collected annually using soil augers,passed through a 2mm sieve,and stored at 4℃ for analysis.The activities of soil extracellular enzymes,including β-1,4-glucosidase(BG),N-acetyl-β-D-glucosaminidase(NAG),leucine aminopeptidase(LAP),and acid phosphatase(ACP),were measured using a microplate reader;soil pH,organic carbon,tot al nitrogen,and available phosphorus were determined following standard methods.One-way ANOVA was conducted to as sess the effects of nitrogen application on soil properties and extracellular enzyme activities.Pearson correlation analysis w as employed to explore the relationships between soil extracellular enzymes and soil properties,while redundancy analysis(RDA)using R software was performed to identify the most significant factors affecting soil nitrogen application.[Result s]The results indicate that moderate nitrogen application(242 kg N·ha⁻¹·yr⁻¹)significantly enhances soil extracellular enzy me activities,particularly LAP,NAG,and ACP,thereby promoting the transformation and mineralization of soil carbon,nit rogen,and phosphorus.This suggests that appropriate nitrogen application can enhance microbial decomposition capabilities and nutrient release efficiency.Conversely,high nitrogen application rates(726 kg N·ha⁻¹·yr⁻¹)inhibited certain enzyme act ivities,leading to decreased nutrient availability in the soil,which could have negative implications for the ecosystem.RD A results further revealed significant correlations between extracellular enzyme activities and nutrient contents,such as soil organic carbon and available nitrogen.[Conclusion]This study uncovers the complex impacts of nitrogen application on e xtracellular enzyme activities and nutrient cycling in bamboo forests.Moderate nitrogen application not only facilitates the transformation and availability of soil nutrients but also helps maintain the health of the soil ecosystem.In contrast,excess ive nitrogen application may induce negative feedbacks,reducing microbial activity and extracellular enzyme function,there by affecting nutrient cycling efficiency.Therefore,to promote soil health and the sustainable productivity of bamboo forest s,nitrogen application rates should be maintained at moderate levels.Future research should further explore the long-term effects of different nitrogen strategies on extracellular enzyme activities and their applicability across various soil types to provide more targeted management recommendations.