Soil carbon storage capacity of drylands under altered fire regimes
Adam F. A. Pellegrini, Peter B. Reich, Sarah E. Hobbie, Corli Coetsee, Benjamin J. Wigley, Edmund C. February, Katerina Georgiou, César Terrer, E. N. Jack Brookshire, Anders Ahlström, Lars Nieradzik, Stephen Sitch, Joe R. Melton, Matthew Forrest, Fang Li, Stijn Hantson, Chantelle Burton, Chao Yue, Philippe Ciais, Robert B. Jackson
Abstract
Abstract The determinants of fire-driven changes in soil organic carbon (SOC) across broad environmental gradients remains unclear, especially in global drylands. Here we combined datasets and field sampling of fire-manipulation experiments to evaluate where and why fire changes SOC and compared our statistical model to simulations from ecosystem models. Drier ecosystems experienced larger relative changes in SOC than humid ecosystems—in some cases exceeding losses from plant biomass pools—primarily explained by high fire-driven declines in tree biomass inputs in dry ecosystems. Many ecosystem models underestimated the SOC changes in drier ecosystems. Upscaling our statistical model predicted that soils in savannah–grassland regions may have gained 0.64 PgC due to net-declines in burned area over the past approximately two decades. Consequently, ongoing declines in fire frequencies have probably created an extensive carbon sink in the soils of global drylands that may have been underestimated by ecosystem models.