An 8000 Year History of Fire and Productivity in a Nutrient-Poor Boreal Landscape Reconstructed from Two Lakes in Central Labrador.

Abstract:

Fire plays an important role in many boreal ecosystems, and fire severity depends on productivity and climate. The boreal forest region of eastern Canada is characterized by both poor soils and a cool, moist climate, suggesting that fire may be less common than in other regions. We collected sediment cores from Canoe (elev. 152 m) and Big Beer (elev. 411 m) lakes and analyzed cores for charcoal, carbon, d¹⁵C, biogenic silica, and magnetics. The sediment record for both lakes dated to ~9000 calibrated years BP, and sediment accumulation rates were low for both lakes (40 and 95 yrs cm^-1). Biogenic silica and carbon data indicate nearly simultaneous increases in lake and terrestrial productivity from ~8000-7000 BP. As indicated by charcoal, fire was present in the landscape as early as 8500 BP. Fire was more common at the lower elevation Canoe site and largely absent from the higher elevation Big Beer site. Average charcoal accumulation rates at both sites (< 0.01 mm² cm^-2 yr^-1) were < 50% of those previously reported for boreal forest sites in more western Canada. Our results support a reduced role for fire in this landscape although it is yet unclear whether poor soils or climate are more directly causal.