N2O emission associated with shifts of bacterial communities in riparian wetland during the spring thawing periods.

Abstract

Soil freeze-thaw processes lead to high nitrous oxide (N2O) emissions and exacerbate the greenhouse effect. The wetlands of the Inner Mongolia Plateau are in the pronounced seasonal freeze-thaw zone, but the effect of spring thaw on N2O emissions and related microbial mechanisms is still unclear. We investigated the effects of different periods (freeze, freeze-thaw, and thaw) on soil bacterial community diversity and composition and greenhouse gas emissions during the spring freeze-thaw in the XiLin River riparian wetlands in China by amplicon sequencing and static dark box methods. The results showed that the freeze-thaw periods predominantly impact on the diversity and composition of the bacterial communities. The phyla composition of the soil bacteria communities of the three periods is similar in level, with Proteobacteria, Chloroflexi, Actinobacteria, and Acidobacteria dominating the microbial communities. The alpha-diversity of bacterial communities in different periods varies that the freezing period is higher than that of the freeze-thaw period (p < .05). Soil total carbon, soil water content, and microbial biomass carbon were the primary factors regulating the abundance and compositions of the bacterial communities during spring thawing periods. Based on functional predictions, the relative abundance of nitrification and denitrification genes was higher in the freezing period than in the thawing period, while the abundance was lowest in the freeze-thawing period. The correlation results found that N2O emissions were significantly correlated with amoA and amoB in nitrification genes, indicating that nitrification may be the main process of N2O production during spring thaw. This study reveals potential microbial mechanisms of N2O emission during spring thaw and provides data support and theoretical basis for further insight into the mechanism of N2O emission during spring thaw.