Feedback processes between climate, surface and vegetation at the northern climatological tree-line (Finnish Lapland)

In northern ecosystems near the climatological timberline, the interactions between vegetation and disturbances, such as forest fire, are particularly important, as the changes in vegetation may produce large feedbacks into the climate. The changed climate and the altered surface conditions may in turn prevent the vegetation from returning to its original state. The effect of fire on local climate and its implications for forest regeneration were studied in the Tuntsa area of Finnish Lapland that was affected by a widespread forest fire in 1960. Direct measurements were applied for determining the variation of climate parameters in a spruce-covered fire refuge and on the treeless tundra environment resulting from the fire. The annual and seasonal dynamics of heat and water fluxes, snow conditions and radiation processes were simulated using an SVAT model known as COUP. Fire-induced deforestation increased the wind velocity by 60%, changed the soil thermal regime through a 20–30 cm reduced snow cover, lowered the evapotranspiration and diminished the Bowen ratio to 0.4. The resulting severe local climate is probably one of the precluding factors in the recovery of the forest in this sensitive region.