Heavy rainfall in peak growing season had larger effects on soil nitrogen flux and pool than in the late season in a semiarid grassland

Authors: LI, L.F. - University Of Chinese Academy Of Sciences; HAO, Y.B. - University Of Chinese Academy Of Sciences; ZHENG, Z. - University Of Chinese Academy Of Sciences; WANG, W - Griffiths University; Biederman, Joel; WANG, Y. - University Of Chinese Academy Of Sciences; WEN, F. - University Of Chinese Academy Of Sciences; QIAN, R. - University Of Chinese Academy Of Sciences; XU, C. - University Of Chinese Academy Of Sciences; ZHANG, B. - University Of Chinese Academy Of Sciences; SONG, X. - University Of Chinese Academy Of Sciences; CUI, X. - University Of Chinese Academy Of Sciences; XU, Z. - Griffiths University

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2021
Publication Date: 11/25/2021
Citation: Li, L., Hao, Y., Zheng, Z., Wang, W., Biederman, J.A., Wang, Y., Wen, F., Qian, R., Xu, C., Zhang, B., Song, X., Cui, X., Xu, Z. 2021. Heavy rainfall in peak growing season had larger effects on soil nitrogen flux and pool than in the late season in a semiarid grassland. Agriculture, Ecosystems and Environment. 326. Article 107785. https://doi.org/10.1016/j.agee.2021.107785.
DOI: https://doi.org/10.1016/j.agee.2021.107785

Interpretive Summary: Nitrous oxide (N2O) is a key greenhouse gas which is more than 250 times as potent as the more well-studied carbon dioxide (CO2). Wet soil is one of the primary sources of N2O to Earth’s atmosphere. As many locations on Earth experience more extreme weather, including intense, heavy rainfall, it is important to understand how this impacts N2O emissions. Here we conducted a 3-year field experiment in which heavy rainfall over 20 days was applied to plots in a semiarid grassland. We found that a mid-summer heavy rainfall increased N2O emissions due to enhanced activity of nitrogen cycling microbes in the soil, whereas late summer heavy rainfall had minimal effects. These results imply that the seasonal timing of increasingly common extreme weather events is important, and heavy rainfall events, such as hurricanes, may represent a positive feedback to global warming.

Technical Abstract: Nitrous oxide (N2O) is a key greenhouse gas and increases in N2O emissions could result in global warming and increased extreme precipitation events, such as short-term heavy rainfalls. However, the effects of heavy rainfalls on N2O fluxes are poorly understood, particularly with regards to high rainfall timing under field conditions. Here, we conducted a 3-y manipulative experiment in which heavy rainfall was respectively imposed in middle and late growing season in a semiarid grassland to explore N2O flux responses and the underlying microbial mechanisms. We found that mid-season heavy rainfall obviously promoted soil N2O emissions, mainly attributed to increases in denitrifying nirK and nirS abundances at higher soil water contents. However, archaeal and bacterial amoA and narG genes did not change significantly due to counteracting effects of increased soil water content (positive) and soil pH (negative). Enhanced accumulated gaseous emissions and probably leaching under mid-season heavy rainfall led to reduction in soil total N. In contrast, late-season heavy rainfall did not change N2O emissions and soil total N contents even though soil water content, soil pH and nirK and nirS abundance were significantly increased, perhaps due to limitation by low temperature. Our results highlight that heavy rainfall timing during the plant growing season strongly regulates N2O emission responses and that increase in heavy rainfalls in the middle part of the growing season may potentially cause a positive feedback to global warming and exacerbate N limitation in terrestrial ecosystems.