How have past fire disturbances contributed to the current carbon balance ofboreal ecosystems?

[摘要] Boreal fires have immediate effects on regionalcarbon budgets by emitting CO₂ into the atmosphere at the time ofburning, but they also have legacy effects by initiating a long-term carbonsink during post-fire vegetation recovery. Quantifying these differenteffects on the current-day pan-boreal (44–84° N) carbon balance andquantifying relative contributions of legacy sinks by past fires is importantfor understanding and predicting the carbon dynamics in this region. Here weused the global dynamic vegetation model ORCHIDEE–SPITFIRE (OrganisingCarbon and Hydrology In Dynamic Ecosystems – SPread and InTensity of FIRE) to attribute the contributionsby fires in different decades between 1850 and 2009 to the carbon balance of2000–2009, taking into account the atmospheric CO₂ change and climatechange since 1850. The fire module of ORCHIDEE–SPITFIRE was turned off for each decade in turn and was also turned off before and after thedecade in question in order to model the legacy carbon trajectory by fires in each pastdecade. We found that, unsurprisingly, fires that occurred in 2000–2009 area carbon source (−0.17 Pg C yr⁻¹) for the carbon balance of2000–2009, whereas fires in all decades before 2000 contribute carbon sinkswith a collective contribution of 0.23 Pg C yr⁻¹. This leaves a netfire sink effect of 0.06 Pg C yr⁻¹, or 6.3 % of the simulatedregional carbon sink (0.95 Pg C yr⁻¹). Further, fires with an age of10–40 years (i.e., those that occurred during 1960–1999) contribute morethan half of the total sink effect of fires. The small net sink effect offires indicates that current-day fire emissions are roughly balanced outby legacy sinks. The future role of fires in the regional carbon balance remainsuncertain and will depend on whether changes in fires and associated carbonemissions will exceed the enhanced sink effects of previous fires, both beingstrongly affected by global change.

[学科分类] 地球化学与岩石