Soil greenhouse gas (GHG) fluxes relate to soil carbon and nitrogen budgets and have a significant impact on climate change. Nevertheless, the temporal variation and magnitude of the fluxes of all three major GHGs (CO
2, CH
4 and N
2O) and their influencing factors have not been elucidated clearly in primary forests on the eastern Qinghai-Tibetan Plateau. Herein, field chamber GHG fluxes from May to November, soil microbial community and enzyme activity were analyzed in a fir-dominated (
Abies fargesii var.
faxoniana) primary forest. The emission rates of CO
2 and N
2O ranged between 64.69–243.22 mg CO
2 m
−2 h
−1 and 1.69–5.46 ug N
2O m
−2 h
−1, exhibiting a temporally unimodal pattern with a peak in July. The soil acted as a CH
4 sink, and the uptake rate varied between 52.96 and 84.67 μg CH
4 m
−2 h
−1 with the higher uptake rates in June and November. The temporal variation in the CO
2 flux was significantly correlated with the geometric mean of enzyme activities, suggesting that the soil CO
2 flux was determined by microbial activity rather than soil microbial biomass. The soil N
2O flux was positively related to nitrate concentration with marginal significance, probably because N
2O was a byproduct of nitrification and denitrification processes. The soil CH
4 uptake was closely associated with methanotrophic biomass (18:1ω7c). The results highlight divergent temporal dynamics of GHG fluxes owing to different driving mechanisms and an important CH
4 sink in the primary forest soil, helping to evaluate the carbon and nitrogen budgets of primary forests on the eastern Qinghai-Tibetan Plateau.
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