Abstract: Exploring the characteristics of soil fertility and labile carbon fractions under different cover crop cultivation modes can provide scientific references for optimizing management of Camellia oleifera forests. We conducted a three-year field experiment with cover crop of Glycine max (DD), Trifolium repens (SY), Helianthus annuus (YK), Cosmos bipinnatus (BJ), with clean tillage as the control (CK), to investigate the changes of physical and chemical properties of topsoil (0-20 cm), the integrated fertility index (IFI), carbon pool management index, labile carbon fractions, and the yield per plant. The results showed that grass cultivation significantly reduced soil bulk density (BD) and increased the content of soil organic carbon (SOC), nitrate-nitrogen, total potassium, and available potassium. Compared with that under clear tillage, the IFIs of BJ and SY increased by 22.4% and 14.0%, respectively. The most significant increase in SOC were observed in BJ and SY, which were 30.1% and 19.3%, respectively. BJ and SY significantly increased but DD and YK significantly decreased carbon pool management index. Moreover, the yield per plant of BJ and YK was much higher than that of clear tillage, with an increase of 19.1% and 21.9%, respectively. Results of correlation analysis and partial least squares path model showed that grass cultivation significantly changed soil physical and chemical properties and increased labile carbon content, which effectively increased fruit yield. In short, grass cultivation could effectively improve soil nutrients and fruit yield. From the perspective of improving soil fertility, BJ and SY were more suitable for grass cultivation in C. olei-fera forests.

Key words: grass cultivation, active carbon component, comprehensive fertility index, carbon pool management index