Soil Carbon Emission Sources Differ Under Litter and Nutrient Addition During Secondary Succession: Evidence from a Mesocosm Study Using a Three-Transfer-Pool Model

A robust understanding of soil organic carbon (C) pools dynamics is important for predicting changes in the C cycle under ongoing climate change. However, the response of different soil C pools to litter and nutrient addition during the long-term secondary succession process remains unclear. We conducted a mesocosm study to reveal the dynamics of different soil C pools. Soil was incubated with litter and nutrient addition collected from five successional stages in the Ziwuling forest region in China. We then used the three-transfer-pool model to simulate C pool dynamics with C emissions data. Litter addition promoted slow C pool emissions during the early stages of secondary succession but inhibited active C pool and passive C pool emissions. Nutrient addition had positive effects on the emissions of C pools, with the exception of passive C pool; nitrogen addition had stronger effects on active C pool, and phosphorus addition had stronger effects on slow C pool. The effects of all addition treatments on the C emissions gradually decreased as succession progressed. The soil C emission sources differed under litter and nutrient addition during secondary succession. The priming effect and nutrient limitation contribute to changes in the soil C cycle.