The role of nosZ I carrying microorganisms in regulating nitrous oxide reduction during forest conversion: A comparison of plantations and secondary forest in subtropical soils

The conversion of natural forests in subtropical regions into plantations or secondary forests has resulted in alterations in soil variables, microbial communities, and microbially-mediated processes, including nitrous oxide (N2O) emissions. However, how forest conversion influences soil N2O reduction and the abundance and community structure of N2O reducing microorganisms remains unclear. Here, we investigated the impact of converting a natural forest to secondary forest, Cunninghamia lanceolata and Pinus massoniana plantations on the abundance and community structure of N2O reducing microorganisms in both bulk soils and aggregates. Compared with secondary forest, plantations had higher soil pH, available phosphorus and moisture content, and lower soil NH4+ content, but similar aggregate sizes. Compared with secondary forest, forest conversion into plantations resulted in significantly higher soil N2O reduction rate and increased abundances of nosZ I and nosZ II in soils and aggregates. The abundance of nosZ I was higher than nosZ II in all tested soils and had a stronger association with N2O reduction rates, suggesting the greater role of nosZ I carrying microorganisms in N2O consumption. Forest conversion had a greater impact on the community composition of nosZ I than nosZ II, mainly by increasing the relative abundance of alpha- and beta-Proteobacteria, while decreasing gamma-Proteobacteria. However, nosZ II carrying microorganisms were exclusively dominated by Gemmatimonadetes and less affected by forest conversion. Taken together, our findings significantly contribute to our understanding of the eco-physiological characteristics of N2O reducing microorganisms and highlight the importance of nosZ I carrying microorganisms in N2O consumption in subtropical forest soils.