Increased litterfall contributes to carbon and nitrogen accumulation following cessation of anthropogenic disturbances in degraded forests

Abstract

Litterfall production constitutes a significant component of net primary production and is a fundamental process in the global carbon and nutrient cycles of terrestrial ecosystems. Recent studies have demonstrated that the cessation of anthropogenic disturbances including selective harvesting, fuelwood collection, and grazing in degraded forests has led to increased forest cover and soil carbon and nitrogen. Despite the importance of litterfall in terrestrial ecosystems, the dynamics of litterfall production and its contribution to soil carbon and nitrogen following the cessation of anthropogenic disturbances in degraded forests remain poorly understood. We used a chronosequence to examine the litterfall dynamics since the cessation of anthropogenic disturbances in the subtropical forests of Eastern China. We found that annual litterfall production increased significantly from 2.5 Mg ha−1 year−1 in stands with recurring disturbances to 4.5 Mg ha−1 year−1 in stands after 31 years of cessation of disturbances, i.e., approximately 80% increase in litterfall production. The increased litterfall production resulted from increasing shrub cover and stand basal area and canopy succession following restoration. The increase in litterfall production contributed to the increased contents and stocks of soil organic matter, carbon, and nitrogen, which increased in the topsoil (0–10 cm) by 200%, 30%, and 150%, respectively, after 31 years of restoration. Our results show evidence for increased annual litterfall production due to the increased stand basal area and shrub cover and canopy succession from pioneer to late-successional species following the cessation of anthropogenic disturbances in the degraded forests. Our results suggest that the increased litterfall production contributed strongly to the accumulation of organic matter, carbon, and nitrogen in the soil following the cessation of anthropogenic disturbances.