Drought, heat, and management interact to affect soil carbon and nitrogen losses in a temperate, humid climate

Authors: LAZICKI, PATRICIA - University Of Tennessee; LEE, JAEHOON - University Of Tennessee; Mengistu, Alemu; JAGADAMMA, SINDHU - University Of Tennessee

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2023
Publication Date: 5/13/2023
Citation: Lazicki, P.A., Lee, J., Mengistu, A., Jagadamma, S. 2023. Drought, heat, and management interact to affect soil carbon and nitrogen losses in a temperate, humid climate. Applied Soil Ecology. https://doi.org/10.1016/j.apsoil.2023.104947.
DOI: https://doi.org/10.1016/j.apsoil.2023.104947

Interpretive Summary: In this study, our goal was to test how drought and heat stress each and combined change the carbon and nitrogen cycling functions and microbial community structure in a soil of a humid climate and the extent to which those changes are affected by management. We evaluated several combinations of carbon and nitrogen cycling under drought with or without heat stress in a conventionally and organically managed arable forest site. Combinations of carbon and nitrogen cycling, potential mineralization, enzyme activities, microbial biomass, dissolved organic carbon and nitrogen, and microbial community structure were assessed during and at the end of the stress period and after rewetting. Our study showed that adding heat to drought stress increased post-wetting carbon and especially nitrogen mineralization compared to soils kept at a reference moisture or drought alone. In addition, we found that stress had little effect on microbial community structure, and the processes returned rapidly to normal levels after both stresses. Our results also suggest that weather events accompanied by more intense rainfall may induce short-term carbon and nitrogen cycle separation and increase the risk of losses. These results indicate an increased potential for separation of carbon and nitrogen cycling when drought occurs at high temperatures, that is critical in unmanaged systems to sustain microbial populations. These results provide additional knowledge that could benefit the scientific community working on climate change.

Technical Abstract: Some areas with historically mesic climates are predicted to experience more climate extremes, including longer droughts combined with hotter days and more intense precipitation. Drought and rewetting are known to alter carbon (C) and nitrogen (N) cycling. However, little information is available on how the effects of drought on C and N cycling differ with temperature and land use in soils from humid regions. We evaluated several metrics of C and N cycling under drought with or without heat stress in a forest site and conventionally and organically managed arable sites. We sampled undisturbed soil cores from 0-10 cm and incubated them under either reference conditions (REF), drought (DRT), or drought combined with heat stress (D+H). Metrics of C and N cycling, including actual and potential mineralization, enzyme activities, microbial biomass, and dissolved organic C and N, and microbial community structure were assessed at the end of the stress period and 14 and 28 d after rewetting. We found that the effects of D+H differed in magnitude and direction from those of DRT: cumulative C and N mineralization followed the order DRT