Fire and soil erosion history in East Canadian boreal
and temperate forests.
Christopher Carcaillet, Pierre J.H. Richard, H. Asnong, Lidia Capece, Yves Bergeron.
Fire-made soil erosion should trigger (i) an increase of inorganic sedimentation within lake-basins and (ii) a change of magnetic
susceptibility if the burn depth is strong enough to reach the mineral soil and to modify the magnetism of mineral particles. Magnetic
susceptibility will also change with the flux of mineral sediments even without a change of their magnetism. Here, we test the role of fire
on soil erosion by measuring the mineral accumulation and the magnetic susceptibility in sediments from seven small lakes’ and two
dunes’ profiles from East Canada over the Postglacial. Four sites are located in the boreal forest south of James Bay, two in the eastern
maritime Quebec and one in the cold temperate south-eastern Ontario. Charcoal accumulation rate is used as a proxy of biomass burning
based on the assumption that higher the biomass burning, higher is the charcoal accumulation. The mineral accumulation, deduced from
loss-on-ignition residues, is a proxy of erosion process in the lake catchment areas. No relationship is observed between sediment types,
sedimentation, magnetic susceptibility and charcoal concentrations in lakes. The patterns of erosion proxies do not match with those of
fire, except in dunes. The results suggest that fires have no significant impact on soil erosion in East Canadian forest ecosystems, except in
dry-sandy areas. This fact can result from fire severity that is not strong enough to completely burn the humus layer, especially in
northern boreal forest characterized by thick soil organic layers. Fire is thus not a significant process affecting the lake sedimentation by
soil material input, nor a factor of soil dynamics by rejuvenation of top most soil centimeters over the Postglacial, except in dry sandy
areas where dune activity is obviously controlled by burning.
r 2006 Elsevier Ltd. All rights reserved.