Widespread enhancement of ecosystem carbon fluxes during post moisture pulse

Authors: BAI, Y. - Chinese Academy Of Sciences; ZHANG, F - Beijing Normal University; CIAIS, P. - Université Paris-Saclay; WIGNERON, J - University Of Bordeaux; FELDMAN, A - University Of Maryland; GENTINE, P. - Columbia University - New York; SMITH, W - University Of Arizona; Biederman, Joel; Scott, Russell; STOY, P - University Of Wisconsin; YAKIR, D. - Weizmann Institite Of Science; KEMANIAN, A - Pennsylvania State University; MAKOWSKI, D. - Université Paris-Saclay; YI, C - City University Of New York; FU, Z - Chinese Academy Of Sciences

Submitted to: Communications Earth & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2026
Publication Date: 1/14/2026
Citation: Bai, Y., Zhang, F., Ciais, P., Wigneron, J.P., Feldman, A.F., Gentine, P., Smith, W.K., Biederman, J.A., Scott, R.L., Stoy, P.C., Yakir, D., Kemanian, A.R., Makowski, D., Yi, C., Fu, Z. 2026. Widespread enhancement of ecosystem carbon fluxes during post moisture pulse. Communications Earth & Environment. 7. Article 171. https://doi.org/10.1038/s43247-026-03191-x.
DOI: https://doi.org/10.1038/s43247-026-03191-x

Interpretive Summary: During extended periods following rainfall events, soil moisture declines, yet its impacts on carbon dioxide and water flows between the ecosystems and the atmosphere remains unclear. To determine these impacts, we use a global database of site-based measurements to isolate a collection of thousands of soil drying events across a large variety of different ecosystems. We quantify the responses of carbon and water fluxes during soil dry-downs. Across the sites, we find higher carbon and water flows during the early stage of soil drying relative to periods without soil drying. Ecosystem carbon gain increases more than carbon loss. This net enhancement in productivity persists for several days before gradually declining. Water loss to the atmosphere also increases during the early stage of soil drying. The enhancement of carbon and water fluxes is much larger in non-arid than in arid sites. Additional analysis of using earth monitoring satellites and computer models were consistent with site data, but models often underestimate its magnitude. These findings have important implications for understanding carbon and water dynamics in the context of increasingly intense and prolonged soil drying around the world.

Technical Abstract: Rainfall pulses generate rapid increases and subsequent declines in soil moisture (SM), yet global ecosystem responses during SM dry-downs remain poorly quantified. Using 6502 soil dry-down events identified from global eddy-covariance observations, we compared carbon fluxes during dry-downs (treatment) to fluxes during the same periods without dry-downs in other years (control). During early dry-downs days, gross primary production (GPP) and respiration both exceeded controls, with stronger GPP gains enhancing net carbon uptake. This enhancement persisted for several days before diminishing as SM decreased and atmospheric dryness intensified. Latent and sensible heat fluxes also rose initially, but latent heat enhancement weakened over time, accompanied by enhanced sensible heat. Machine-learning analyses show that photosynthetic capacity and radiation drive positive GPP anomalies, while water limitations induce negative ones. Satellite data supported these patterns, whereas Earth system models underestimate their magnitude. These findings highlight transient pulse responses and support the broader applicability of the pulse-reserve paradigm.