The frequency of forest fires in Scots pine stands of Tuva, Russia

Abstract

Forest fires resulting from long periods of drought cause extensive forest ecosystemdestruction and can impact on the carbon balance and air quality and feed back to theclimate system, regionally and globally. Past fire frequency is reconstructed for TuvanScots pine stands using dendrochronology and statistics. Central Tuvan Scotspine (Pinus sylvestris) stands are subject to annual fire regimes; however highintensity fires are rare but they are responsible for most of the damage. Low,medium, and high severity fires have shaped the multi-story Scots pine communities,locally and regionally. Fire type and frequency are directly related to weather andclimate and are also dependent on anthropogenic influences. The primary dryperiod, which promotes fire ignition and spread, in Tuva occurs in April andMay. In some years, the precipitation deficit combined with high air temperaturesinduces long periods of drought. Unlike the typical surface fire regime, forest firesthat burn during these extreme droughts often become crown fires that resultin substantial forest damage and carbon release. The mean fire interval (MFI)is found to be 10.4 years in Balgazyn stands, and the landscape-scale MFI is22.4 years. High severity, stand-replacing crown fires have a longer MFI. Thewarmer and dryer weather that is predicted by global climate models is evident inTuva, and we believe that these changes in weather and climate have resulted inincreased fire intensity and severity, rather than fire frequency in the Tuvan region.