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Fire suppression and fuels treatment effects on mixed‐conifer carbon stocks and emissions
Author(s) -
North Malcolm,
Hurteau Matthew,
Innes James
Publication year - 2009
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/08-1173.1
Subject(s) - thinning , environmental science , understory , carbon sink , carbon sequestration , prescribed burn , agroforestry , greenhouse gas , fire regime , carbon fibers , climate change mitigation , fire protection , climate change , forestry , ecology , carbon dioxide , ecosystem , biology , geography , canopy , materials science , engineering , civil engineering , composite number , composite material
Depending on management, forests can be an important sink or source of carbon that if released as CO 2 could contribute to global warming. Many forests in the western United States are being treated to reduce fuels, yet the effects of these treatments on forest carbon are not well understood. We compared the immediate effects of fuels treatments on carbon stocks and releases in replicated plots before and after treatment, and against a reconstruction of active‐fire stand conditions for the same forest in 1865. Total live‐tree carbon was substantially lower in modern fire‐suppressed conditions (and all of the treatments) than the same forest under an active‐fire regime. Although fire suppression has increased stem density, current forests have fewer very large trees, reducing total live‐tree carbon stocks and shifting a higher proportion of those stocks into small‐diameter, fire‐sensitive trees. Prescribed burning released 14.8 Mg C/ha, with pre‐burn thinning increasing the average release by 70% and contributing 21.9–37.5 Mg C/ha in milling waste. Fire suppression may have incurred a double carbon penalty by reducing stocks and contributing to emissions with fuels‐treatment activities or inevitable wildfire combustion. All treatments reduced fuels and increased fire resistance, but most of the gains were achieved with understory thinning, with only modest increases in the much heavier overstory thinning. We suggest modifying current treatments to focus on reducing surface fuels, actively thinning the majority of small trees, and removing only fire‐sensitive species in the merchantable, intermediate size class. These changes would retain most of the current carbon‐pool levels, reduce prescribed burn and potential future wildfire emissions, and favor stand development of large, fire‐resistant trees that can better stabilize carbon stocks.