Long-Term Perspectives on Fire-Climate-Vegetation Relationships in the North American Boreal Forest

Abstract

The ecological role of fire in the modern boreal forest has been reviewed by several authors (Wright and Heinselman 1973; Wein and MacLean 1983; Johnson 1992, Payette 1992). Wildfire and climate are intimately linked (Swetnam 1993). Shorter-term weather patterns are clearly an important determinant of fire activity at daily-to-monthly time scales. At longer time scales of decades and centuries, Swetnam (1993) has shown that fire occurrence in Giant Sequoia groves was related to climate. However, other factors such as topography and fuel play a role in the fire regime. Fuel type, structure, moisture, accumulation, density, flammability, and continuity can affect the fire regime.1 An extreme example highlighting the role of fuel can be found in many deserts where fires should be frequent due to the hot and dry environment but are absent because there is no fuel. Therefore, climate controls fire directly through opportunities for ignition and spread but also through regulation of the accumulation and structure of fuel at decadal or greater time scales.