The important role of soil carbon pools in coping with climate change has become widely recognized. Moso bamboo (Phyllostachys pubescens) is an economically important bamboo species in South China; however, owing to factors such as rising labor costs and increasingly stringent environmental policies, Moso bamboo forests have recently been abandoned. The present study aimed to investigate the effects of abandonment on structural factors and soil organic carbon (SOC) stocks in Moso bamboo forests. We investigated Moso bamboo forests subjected to intensive management or abandonment for different durations and measured forest structural characteristics, mineral properties, soil nutrients, and other soil properties. Although abandonment did not significantly affect the height and diameter at breast height, it increased culm densities, biomass, and SOC stocks. The drivers of SOC stocks depended on soil depth and were mainly controlled by carbon decomposition mediated by soil properties. In the topsoil, mineral protection and soil total nitrogen (TN) exerted significant effects on SOC stocks; in the subsoil, soil TN was the main driver of SOC stocks. As the controlling factors of SOC stocks differed between the subsoil and topsoil, more attention should be paid to the subsoil. Overall, these findings refine our understanding of the structural characteristics and SOC stocks associated with Moso bamboo forest abandonment, serving as a reference for the follow-up management of these forests.

Biochar, a soil conditioner, has the potential to improve soil properties and plant productivity. However, in forestry planting, especially in subtropical moso bamboo forests, the response of seedling growth to biochar addition is still not well known. We conducted a comprehensive factorial experiment with biochar and nitrogen (N) addition as factors (no biochar and no N addition; 0.64% biochar + 0% NH₄NO₃; 1.28% biochar + 0% NH₄NO₃; T3: 0% biochar + 1.28% NH₄NO₃; T4: 0.64% biochar + 1.28% NH₄NO₃; T5: 1.28% biochar + 1.28% NH₄NO₃) to study their effects on moso bamboo seedling growth, rhizosphere soil nutrient contents, and enzymatic activity. Our results indicate that applying biochar without N did not promote the growth of moso bamboo seedlings (biomass of leaves and branches) but increased soil nutrient content and affected soil-enzyme activity. The combined application of biochar and N significantly increased the leaf and branch biomass of moso bamboo seedlings and soil nutrient content and affected soil-enzyme activity. In conclusion, biochar should be mixed with an adequate amount of N for its application in subtropical moso bamboo forests to promote seedling growth and improve economic benefits.