Microbial community and associated enzymes activity influence soil carbon chemical composition in Eucalyptus urophylla plantation with mixing N2-fixing species in subtropical China

Background and aims

Microbial communities and their associated enzyme activities affect the quantity and chemical quality of carbon in soil. We aimed to evaluate the biochemical mechanisms underlying how N₂-fixing species influences soil organic carbon chemical composition through soil microbial functional groups and enzyme activities.

Methods

We examined the effects of N₂-fixing species mixed with Eucalyptus on soil carbon storage, and the chemical composition of an 8-year-old pure Eucalyptus urophylla plantation (PP) and a mixed E.urophylla and Acacia mangium plantation (MP).

Results

The soil carbon stock and recalcitrant carbon chemical component significantly increased in surface soil in MP. The total PLFAs and bacterial PLFAs increased by 29.1% and 27.0% in cool-dry season, while in the warm-wet season, the total PLFAs and bacterial PLFAs increased by 13.1% and 27.3%, respectively. However, the fungal PLFAs decreased significantly in warm-wet season in MP. The total activity of the cellulose-degrading enzyme β-glucosidase was significantly greater with mixed N₂-fixing species in both dry-cool and wet-warm season. The increase in the Alk-C/O-Alk-C ratio and SOC was strongly associated with both C-acquisition activity and bacterial community.

Conclusions

Our findings highlight the importance of N₂-fixing species in regulating both soil microbial communities and their functioning in association with soil extracellular enzyme activities, which contribute to the increased soil carbon storage and recalcitrant carbon composition in Eucalyptus plantations.