The history and pattern of fire in the boreal forest of southeastern Labrador

Abstract

The fire history of the wilderness of southeastern Labrador is marked by a patchy distribution of large fires in time and space. During the 110-year period encompassed by this study, major fires occurred in four decades, 1870–1879, 1890–1899, 1950–1959, 1970–1979. From 1900 to 1951 only 1125 km2 burned; this represents approximately 10% of the total area consumed from 1870 to 1980. Fire records indicate an asynchroneity of the important fire years in southeastern Labrador and adjacent provinces and within Labrador itself. This observation suggests that the meteorological conditions controlling fire occurrence in this portion of the eastern boreal forest are local in nature and extent. The fire rotation for southeastern Labrador is calculated at approximately 500 years, significantly longer than that estimated for other regions of boreal forest. The rare occurrence of large fires is explained by high levels of precipitation and by the preponderance of fire breaks, primarily lakes and peatlands. On the basis of physiographic criteria the region is subdivided into two types of landscape displaying contrasting fire regimes. The large interior plateau, which is covered by extensive peatlands and numerous lakes, has a low fire incidence and extremely long fire rotation. In contrast, large fires are common in the watersheds of the Alexis, Paradise, and St. Augustin rivers where the topographic relief is quite varied and peatlands are scarce. The regional pattern of fire activity has important phytogeographical implications. The lichen woodlands and birch forests are fire-dependent vegetation types; their distribution in the modern landscape is strongly correlated with the historical occurrence of fire during the past 110 years. In addition it is postulated that the historical absence of fire across the large plains in southeastern Labrador has contributed to the development of extensive peatlands in these areas.