title: Management Impacts on Carbon Dynamics in a Sierra Nevada Mixed Conifer Forest.
abstract: Forest ecosystems can act as sinks of carbon and thus mitigate anthropogenic carbon emissions. When forests are actively managed, treatments can alter forests carbon dynamics, reducing their sink strength and switching them from sinks to sources of carbon. These effects are generally characterized by fast temporal dynamics. Hence this study monitored for over a decade the impacts of management practices commonly used to reduce fire hazards on the carbon dynamics of mixed-conifer forests in the Sierra Nevada, California, USA. Soil CO2 efflux, carbon pools (i.e. soil carbon, litter, fine roots, tree biomass), and radial tree growth were compared among un-manipulated controls, prescribed fire, thinning, thinning followed by fire, and two clear-cut harvested sites. Soil CO2 efflux was reduced by both fire and harvesting (ca. 15%). Soil carbon content (upper 15 cm) was not significantly changed by harvest or fire treatments. Fine root biomass was reduced by clear-cut harvest (60-70%) but not by fire, and the litter layer was reduced 80% by clear-cut harvest and 40% by fire. Thinning effects on tree growth and biomass were concentrated in the first year after treatments, whereas fire effects persisted over the seven-year post-treatment period. Over this period, tree radial growth was increased (25%) by thinning and reduced (12%) by fire. After seven years, tree biomass returned to pre-treatment levels in both fire and thinning treatments; however, biomass and productivity decreased 30%-40% compared to controls when thinning was combined with fire. The clear-cut treatment had the strongest impact, reducing ecosystem carbon stocks and delaying the capacity for carbon uptake. We conclude that post-treatment carbon dynamics and ecosystem recovery time varied with intensity and type of treatments. Consequently, management practices can be selected to minimize ecosystem carbon losses while increasing future carbon uptake, resilience to high severity fire, and climate related stresses.
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.
authors.forename: Sabina
authors.initials: S
authors.lastname: Dore
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.
authors.forename: Danny L
authors.initials: DL
authors.lastname: Fry
authors.affiliation: United States Department of Agriculture Forest Service, Pacific Southwest Research Station, Davis, California, United States of America.|University of California Center for Fire Research and Outreach, College of Natural Resources, University of California, Berkeley, California, United States of America.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Collins
authors.affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware, United States of America.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Vargas
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.|University of California Berkeley Center for Forestry, Georgetown, California, United States of America.
authors.forename: Robert A
authors.initials: RA
authors.lastname: York
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Stephens
mesh_terms: D018533:Biomass; D002140:California; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism; D017753:Ecosystem; D005390:Fires / Q000517:prevention & control; D016468:Forestry / Q000379:methods* / Q000639:trends; D065928:Forests; D012987:Soil / Q000737:chemistry; D064028:Tracheophyta / Q000254:growth & development / Q000378:metabolism*
chemical_list: D012987:Soil; D002245:Carbon Dioxide