Suppression of AMF accelerates N2O emission by altering soil bacterial community and genes abundance under varied precipitation conditions in a semiarid grassland
Junqin Li, Bo Meng, Xuechen Yang, Nan Cui, Tianhang Zhao, Hua Chai, Tao Zhang, Wei Sun
Abstract
Nitrous oxide (N 2 O) is one of the most important greenhouse gases contributing to global climate warming. Recently, studies have shown that arbuscular mycorrhizal fungi (AMF) could reduce N 2 O emissions in terrestrial ecosystems; however, the microbial mechanisms of how AMF reduces N 2 O emissions under climate change are still not well understood. We tested the influence of AMF on N 2 O emissions by setting up a gradient of precipitation intensity (+50%, +30%, ambient (0%), −30%, −50%, and −70%) and manipulating the presence or exclusion of AMF hyphae in a semiarid grassland located in northeast China. Our results showed that N 2 O fluxes dramatically declined with the decrease in precipitation gradient during the peak growing season (June–August) in both 2019 and 2020. There was a significantly positive correlation between soil water content and N 2 O fluxes. Interestingly, N 2 O fluxes significantly decreased when AMF were present compared to when they were absent under all precipitation conditions. The contribution of AMF to mitigate N 2 O emission increased gradually with decreasing precipitation magnitudes, but no contribution in the severe drought (−70%). AMF significantly reduced the soil’s available nitrogen concentration and altered the composition of the soil bacteria community including those associated with N 2 O production. Hyphal length density was negatively correlated with the copy numbers of key genes for N 2 O production ( nirK and nirS ) and positively correlated with the copy numbers of key genes for N 2 O consumption ( nosZ ). Our results highlight that AMF would reduce the soil N 2 O emission under precipitation variability in a temperate grassland except for extreme drought.