Physical properties of dead and downed round-wood fuels in the Boreal forests of western and Northern Canada

Abstract

The quantity of dead and downed woody fuels in forests is commonly estimated using the line intersect method of sampling. Determination of the mass of wood per unit area for each size class requires values for the mean specific gravity, piece tilt angle and piece diameter. We present these values for dead and downed round-wood materials less than 7 cm in diameter based on surveys of slash and naturally fallen materials in six boreal forest regions of western and northern Canada and for eight common species in these regions. There was considerable variation in the three variables: mean specific gravity ranged from 0.34 to 0.65 Mg m^–3, tilt ranged from 5˚ to 33˚, and mean squared diameter ranged from 31% below to 71% above the value at class mid-point. Values of each were strongly related to size class, species, fuel type and to region. We conclude that values derived from other study areas or species can give substantial inaccuracies in estimating dead and downed round-wood fuel loads if applied to sites within the study region, although ultimate accuracy obtainable will be more influenced by the length of sampling line. The three variables are combined into a single factor so that fuel loads can be simply calculated by multiplying this factor by the number of intersects per metre of transect.