Effects of Different Regenerated Models on Soil Nitrogen Mineralization in Subtropical Evergreen Broad-Leaved Forest

【Objective】The purpose of this study was to explore the changes of soil N mineralization after the conversion of subtropical evergreen broad-leaved forest of Castanopsis carlesii to plantation or forest naturally regenerated with artificial enhancement in order to conclude the advantages in N cycling of artificial enhancement of regeneration over the traditional plantation management, therefore to provide a basis for evaluation and selection of forest management models.【Method】Natural evergreen forest of Castanopsis carlesii(NF), artificially regenerated secondary forest(AR), and Castanopsis carlesii plantation (CC) in Sanming City, Fujian Province were studied. Soil ammonium nitrogen(NH4+-N), nitrate nitrogen (NO3--N) concentrations, and soil N mineralization rate in the surface layer (0-10 and 10-20 cm) among three forest types were compared.【Result】The conversions of NF to AR and CC decreased soil NH4+-N, but increased NO3--N concentration. Compared with NF, the NH4+-N concentration decreased by 5%-13% and 16%-25% in the soil of 0-10 and 10-20 cm respectively, and the NO3--N concentration increased by 1.4%-241% and 68%-871% respectively. The NH4+-N concentration of the AR was 3%-27% higher than that of the CC, and the NO3--N was lower by 40%-65%. Soil net N mineralization rate of the AR and the CC was lower by 11%-12% and 27%-50% after the forest conversion, respectively. The soil net nitrogen mineralization rate of AR was significantly higher than that of CC, and the net nitrification rate was significantly lower than that of CC. 【Conclusion】Compared to the plantation, the artificial regeneration model caused lower human disturbances on soil leading to a higher return of litter nutrients, a higher soil net nitrogen mineralization rate, and a lower net nitrification rate. This results in a high content of inorganic N and improves soil N availability in AR. Therefore, the model of natural regeneration with artificial enhancement is beneficial to soil nitrogen preservation and improvement of nitrogen availability, also advantageous over plantation management in terms of nitrogen cycling. © 2021, Editorial Department of Scientia Silvae Sinicae. All right reserved.