Competition and community succession link N transformation and greenhouse gas emissions in urine patches

Nitrous oxide (N2O) is a strong greenhouse gas produced by biotic and abiotic processes. These processes are directly linked to both fungal and prokaryotic communities that either produce or consume the gas, or create conditions that lead to its emission. In soils exposed to nitrogen (N) in the form of urea, an ecological succession is triggered that results in a highly dynamic system with turnover of microbial populations. However, knowledge of the mechanisms controlling this succession and the repercussions for N2O emissions remain incomplete. Here, we address these knowledge gaps by using soil microcosms exposed to urea and monitored for N2O emissions and community [fungal and prokaryotic] changes. We also determine the contribution of microbes in emissions by applying biological inhibitors. Results confirmed that soils exposed to urea lead to high species turnover with large community re-arrangements for both fungal and prokaryotic communities. Changes revealed a community succession linked to competition between species, with winning species replacing established species. Early to late responders are selected for based on life history strategies, with specific species replacement mediated by competition. Results also identified fungi as significant contributors to N2O emissions, and demonstrate that dominant fungal populations are consistently replaced at different stages of the succession. These successions are affected by addition of inhibitors and resulted in strong decreases in nitrification and co-denitrification suggesting that fungal contributions to these two processes are larger than that of prokaryotes.