Terrestrial N2O emissions and related functional genes under climate change: A global meta-analysis

Authors: LI, L. - Chinese Academy Of Sciences; ZHENG, Z. - Chinese Academy Of Sciences; WANG, W. - Griffiths University; Biederman, Joel; XU, X. - Chinese Academy Of Sciences; RAN, Q. - Chinese Academy Of Sciences; QIAN, R. - Chinese Academy Of Sciences; XU, C. - Chinese Academy Of Sciences; ZHANG, B. - Chinese Academy Of Sciences; WANG, F. - Chinese Academy Of Sciences; ZHOU, S. - Chinese Academy Of Sciences; CUI, L. - Chinese Academy Of Sciences; CHE, R. - Yunnan University; HAO, Y.B. - Chinese Academy Of Sciences; CUI, X. - Chinese Academy Of Sciences; XU, Z.H. - Griffiths University; WANG, Y.F. - Chinese Academy Of Sciences

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2019
Publication Date: 9/25/2019
Citation: Li, L., Zheng, Z., Wang, W., Biederman, J.A., Xu, X., Ran, Q., Qian, R., Xu, C., Zhang, B., Wang, F., Zhou, S., Cui, L., Che, R., Hao, Y., Cui, X., Xu, Z., Wang, Y. 2019. Terrestrial N2O emissions and related functional genes under climate change: A global meta-analysis. Global Change Biology. 26(2):931-943. https://doi.org/10.1111/gcb.14847.
DOI: https://doi.org/10.1111/gcb.14847

Interpretive Summary: Although much climate change research focuses on carbon dioxide, there are other important greenhouse gases occurring in smaller quantities but with greater potency than CO2. In this paper, we synthesize emissions of the greenhouse gas nitrous oxide (N2O) from 46 published studies worldwide in which temperature or precipitation were artificially altered to test for effects on N2O emissions. Many of these studies also tested for microbes in the soil which mediate N2O release. We found that increased temperature drove increased N2O release from soils by an average of 33%, although the results varied across biomes, with the biggest response in shrublands and the least in tundra. To increase N2O emissions, it was necessary to increase temperature 24 hours per day for several months or more. Increased precipitation enhanced N2O emissions, while decreased precipitation suppressed emissions. All of these climate-driven results appeared to be independent of the types of N2O-releasing microbes present. Collectively, these results suggest that globally warming temperatures may increase N2O release, representing a reinforcing effect on climate change.

Technical Abstract: Nitrous oxide (N2O) emissions from soil contribute to global warming and are in turn substantially affected by climate change. However, climate change impacts on N2O production across terrestrial ecosystems remain poorly understood, especially at regional to global scales and in relation to the underlying microbial mechanisms. Here, we synthesised 46 published studies of N2O fluxes and relevant soil functional genes (SFGs, i.e. archaeal amoA, bacterial amoA, nosZ, narG, nirK and nirS) to assess terrestrial ecosystem N2O responses to increased temperature, increased or decreased precipitation amounts, and prolonged drought (no change in total precipitation but increase in precipitation intervals). Across the dataset, temperature increased N2O emissions by 33%. However, the effects were highly variable across biomes, with strongest temperature responses in shrublands, variable responses in forests and negative responses in tundra. The warming methods employed also influenced the effects of temperature on N2O emissions (most effectively induced by open-top chambers). Increased temperature treatments applied during whole days or whole years significantly enhanced N2O emissions, but day, night or short-season warming did not have significant effects. Regardless of biome, treatment method and season, increased precipitation promoted N2O emission by an average of 55%, while decreased precipitation suppressed N2O emission by 31%, predominantly driven by changes in soil moisture. The effect size of precipitation changes on nirS and nosZ showed a U-shape relationship with soil moisture; further insight into biotic mechanisms underlying N2O emission response to climate change remain limited by data availability, underlying a need for studies that report SFG. Given that climate change is manifesting through increasing frequency of extreme events (e.g. heat wave, prolonged drought, heavy rainfall), and that existing climate experiments mainly simulate chronic changes we suggest future studies focused on climate extremes.