Long-term intensive forest management ultimately leads to imbalances in soil nutrient and extracellular enzyme stoichiometry

Intensive management, as a significant approach to forest management, has been widely applied around the world. While this method can enhance forest productivity and economic benefits to some extent, the long-term effects of intensive management on microbial-mediated soil nutrient cycling and extracellular enzyme activity remain unclear. Additionally, there has been limited research on how enzyme activity and soil nutrient availability vary over time in relation to management practices. Therefore, this study focuses on the secondary forests of Carya cathayensis var. dabeishansis, aiming to investigate the effects of management intensity and duration on soil extracellular enzyme activity and soil nutrient dynamics in these forests. In this study, three levels of forest management intensity were applied: CK (no management), EM (extensive management), and IM (intensive management), encompassing five management durations (0 years, 3 years, 8 years, 15 years, and 20 years). The effects of management intensity and duration on enzyme activity and soil nutrients in the 0-10 cm, 10-20 cm, and 20-30 cm soil layers of the secondary forests of C. cathayensis var. dabeishansis were analyzed. Results indicated that management duration is the primary driver for changes in the physicochemical properties and enzyme activity of the soil in the secondary forests of C. cathayensis var. dabeishansis, with increased management intensity amplifying the effects of prolonged management on soil nutrients and extracellular enzyme activity. With the increase in management duration, intensive and extensive management resulted in increased soil bulk density and decreased pH, exacerbating soil compaction and acidification. Soil nutrient levels initially increased and then decreased with management duration, suggesting that short-term management practices are beneficial for improving soil nutrient content and availability. The activity of soil saccharase and β-1,4-glucosidase initially increased and then decreased with management duration under both management practices. At the same time, the activity of urease and protease enzymes in extensive management was significantly higher than that in intensive management. The vector lengths of the soil enzyme stoichiometric characteristics across all forest stands were greater than 1, with vector angles exceeding 45°. Under the same management duration, the vector length and angle for intensive management were significantly higher than those for extensive management and CK. There is a prevalent limitation of microbial C and P in the soil of the secondary forests of C. cathayensis var. dabeishansis, with a stronger limitation effect under intensive management, which significantly increased with management duration.In conclusion, long-term intensive management leads to an imbalance in soil nutrients and extracellular enzyme stoichiometry in the secondary forests of C. cathayensis var. dabeishansis. To maintain the nutrient supply capacity of the soil in these forests and reduce microbial nutrient limitations, it is recommended to appropriately retain understory vegetation, increase the application of phosphorus and organic fertilizers, and reduce nitrogen fertilizer use to maintain soil nutrient balance. Our study provides valuable guidance for nutrient management and sustainable management practices for C. cathayensis var. dabeishansis.