Rapid recovery of gross production and respiration in a mesic mountain big sagebrush ecosystem following prescribed fire

Authors: FELLOWS, AARON; Flerchinger, Gerald; LOHSE, KATHLEEN - IDAHO STATE UNIVERSITY; Seyfried, Mark

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2017
Publication Date: 1/19/2018
Citation: Fellows, A.W., Flerchinger, G.N., Lohse, K., Seyfried, M.S. 2018. Rapid recovery of gross production and respiration in a mesic mountain big sagebrush ecosystem following prescribed fire. Ecosystems. 1-12. https://doi.org/10.1007/s10021-017-0218-9.
DOI: https://doi.org/10.1007/s10021-017-0218-9

Interpretive Summary: The impact of prescribed fire on ecosystem-level carbon cycling is poorly understood in Western US rangelands. At least part of this uncertainty is rooted in a limited understanding of how carbon cycling changes during a multi-year post-burn period when the ecosystem is in recovery. We therefore examined the exchange of carbon dioxide between the land and atmosphere for two years before and seven of nine years following a prescribed fire in a mountain big sagebrush shrubland located in the northern Great Basin, USA. Following the fire, annual gross carbon uptake and carbon loss from the sagebrush recovered to pre-burn levels within 2 years and remained elevated for the remainder of the study. Annual gross carbon uptake was greater than carbon loss before and after the fire, indicating the site sequestered atmospheric carbon dioxide before and after the burn. Re-sprouting and recruitment of grasses and forbs drove the rapid post-burn increase in carbon uptake. Woody shrub growth accumulated aboveground biomass after the fire. These results suggest gross carbon uptake and loss following prescribed fires in mountain big sagebrush ecosystems recover rapidly in areas with an ample water supply and where the ecosystem is not impacted by non-native grass invasion.

Technical Abstract: The impact of land management actions such as prescribed fire remains a key uncertainty in understanding the spatio-temporal patterns of carbon cycling in the Western USA. We quantified the recovery of carbon exchange and aboveground carbon stocks following prescribed fire in a mountain big sagebrush ecosystem located in the northern Great Basin, USA. Specifically, we assessed changes in plant functional type, leaf area index, standing aboveground carbon stocks, Net Ecosystem Production (NEP), Gross Ecosystem Production (GEP), and Ecosystem-level Respiration (Reco) for 2 years before and 7 of 9 years after the prescribed fire. Post-burn GEP and Reco exceeded pre-burn GEP and Reco within 2 years and remained elevated. The variation in GEP and Reco provided no evidence of a large and prolonged net efflux of carbon in the 9 years after the fire. Rather, NEP indicated the site was a sink before and after the fire, with little change in sink strength associated with the burn. Re-sprouting and recruitment of grasses and forbs drove the post-burn increase in GEP. Woody shrub growth was the dominant control on aboveground biomass accumulation after fire, with aboveground biomass reaching ~11% of pre-fire biomass after 5 years. The rapid recovery of GEP and the growth of mid-successional shrubs suggest ecosystem-level carbon fluxes and stocks recover rapidly after fire in mesic mountain big sagebrush ecosystems, ameliorating the atmospheric carbon burden associated with fires in these ecosystems.