Microbial nitrous oxide emissions in dryland ecosystems: mechanisms, microbiome and mitigation

Abstract

Globally, drylands represent the largest terrestrial biome and are projected to expand by 23% by the end of this century. Drylands are characterized by extremely low levels of water and nutrients and exhibit highly heterogeneous distribution in plants and biocrusts which make microbial processes shaping the dryland functioning rather unique compared with other terrestrial ecosystems. Nitrous oxide (N O) is a powerful greenhouse gas with ozone depletion potential. Despite of the pivotal influences of microbial communities on the production and consumption of N O, we have limited knowledge of the biological pathways and mechanisms underpinning N O emissions from drylands, which are estimated to account for 30% of total gaseous nitrogen emissions on Earth. In this article, we describe the key microbial players and biological pathways regulating dryland N O emissions, and discuss how these processes will respond to emerging global changes such as climate warming, extreme weather events and nitrogen deposition. We also provide a conceptual framework to precisely manipulate the dryland microbiome to mitigate N O emissions in situ using emerging technologies with great specificity and efficacy. These cross-disciplinary efforts will enable the development of novel and environmental-friendly microbiome-based solutions to future mitigation strategies of climate change.

Linking NO and N2O emission pulses with the mobilization of mineral and organic N upon rewetting dry soils

“…Table 1), perhaps suggesting that NO3 -was in fact reduced to N2O. It has been suggested that bursts of microbial respiration following a rewetting pulse can rapidly deplete soil oxygen levels, allowing denitrification to occur in anoxic soil microsites and leading to substantial N2O emissions in drylands (Hu et al, 2017).…”

Nitrifier‐induced denitrification is an important source of soil nitrous oxide and can be inhibited by a nitrification inhibitor 3,4‐dimethylpyrazole phosphate

“…Due to the growing demand for greater food production and therefore agricultural expansion, the global consumption of N fertilizers is projected to increase annually at a rate of 1.4% between 2014 and 2018 (FAO, ); this would greatly contribute to the conspicuous elevation in atmospheric N 2 O concentrations (Shcherbak et al ., ). To effectively mitigate N 2 O emissions and to promote the reliable estimation of future N 2 O production, approaches that can accurately differentiate soil N 2 O production from different biological pathways (Hu et al ., , ) are in urgent need.…”

Global drivers of methane oxidation and denitrifying gene distribution in drylands

“…Our study shows an interesting relationship between aridity and nosZ ‐carrying denitrifiers at the global scale, which might result in potential implications for the capacity of drylands to exchange N 2 O with the atmosphere in a changing world. As aridity continues to increase worldwide owing to climate change (Hu, Trivedi, He, & Singh, ), the changes in the abundance and decrease in the richness of the nosZ gene with aridity might reduce the potential of drylands to support complete denitrification of N 2 O to N 2 . Interestingly, unlike a study that has observed a negative impact of increasing soil temperature on the abundance of nosZ genes in a boreal–temperate ecotone (Martins et al, ), we could not detect such an effect in global drylands.…”

“…Furthermore, these numbers are likely to increase substantially in coming decades as a result of climate change‐driven increases in aridity (Huang, Yu, Guan, Wang, & Guo, ) and projected human population growth rates (United Nations, ). In addition, recent evidence suggests that CH 4 and N 2 O fluxes in drylands might be relevant at the global scale, given both the reported process rates and their extent worldwide (e.g., Hu Trivedi, He, & Singh, ; Martins, Nazaries, Macdonald, Anderson, & Singh, ; Weber et al, ).…”