Fire as the dominant driver of central Canadian boreal forest carbon balance

Fire tips the carbon balance Changes in climate, atmospheric carbon dioxide concentration and fire frequency have been occurring for decades in high-latitude (boreal) forests. Previous work has not linked these changes with vegetation competition on a large scale, but a new study uses a computer model to simulate competition between trees and moss across a million square kilometres of Canadian forest. The results show that the carbon balance — the amount of carbon gained or lost by the soil and vegetation — of this region was driven largely by changes in the fire regime, rather than climate or rising CO2, between 1948 and 2005. More frequent and larger fires in the late twentieth century promoted growth of deciduous trees and mosses at the expense of coniferous trees. Poor soil drainage damped the variability of the landscape carbon balance, suggesting that increased climate and hydrological changes can influence the carbon dynamics of these areas disproportionately.