WILDFIRE IN RUSSIAN BOREAL FORESTS - POTENTIAL IMPACTS OF FIRE REGIMECHARACTERISTICS ON EMISSIONS AND GLOBAL CARBON BALANCE ESTIMATES

Most of the research about the effects of the release of carbon and ot her chemicals to the atmosphere during forest fir es focuses on emissi ons from crown fires or slash fires in which a high percentage of the fine fuels are burned However, in many temper-ate and boreal conifer e cosystems, surface fires of varying intensities and severities are an important part of the fire regime. In Russia a large percentage of the area burned in a typical year is in surface fires, which will result in lower carbon emissions than crown fires because of lower fuel consu mption. lit Russian boreal for est, different distribution patterns of fire severity across the landscape could produce fourfold differences in carbon release. Furthermore, tree mortality after surface fires is often quite extensive, leading to a pulse in carbon release as needle s and other fine fuels fall to the ground and decompose. With extensiv e tree mortality a decrease in carbon sequestration is expected for se veral years, until stand level photosynthesis returns to prefire level s. Perhaps the largest potential source of error in estimates of carbo n release from biomass fires in Russia is inaccuracy in estimates of b urned area. Many published estimates of annual burned area in Russia m ay be extremely low. On the basis of information on fire return interv als and area of boreal forest, 12 million ha per year may be a reasona ble conservative estimate of burned area until better data are availab le. Based on this estimate, direct and indirect fire-generated carbon emissions from boreal forests worldwide may exceed 20% of the estimate d global emissions from biomass burning, making them an important comp onent in understanding global atmospheric chemistry. In considering ef fects of fire an global atmospheric chemistry, it is important to incl ude the effects of fire severity, postfire mortality, decomposition of fine fuels, and changing postfire vegetation structure as components of fire-induced changes in ecosystem-level carbon flux. But the most i mportant factor may be accurate information on the annual area burned. Levels of carbon storage are likely to be highly sensitive to changes in fire return intervals that result from direct human activities and from climatic changes, making accurate assessments of burned areas an d fire severity critical. Strong fire management programs will be key to managing future fire regimes and carbon cycling in Russia's boreal forest. Published by Elsevier Science Ltd.