Conversion of dense lodgepole pine stands in west-central British Columbia into young lodgepole pine plantations using prescribed fire. 1. Biomass consumption during burning treatments

The ecological effects of different treatments used to convert dense Pinuscontorta var. latifolia Engelm. stands into young P. contorta plantations are determined. The treatments used were felling the trees with a bulldozer and either broadcast burning the slash or bulldozing the slash into windrows, which were then burned. Burns were conducted under different fuel moisture conditions and state of fuel curing to achieve four classes of fire severity. The preburn surface fuel load was relatively high due largely to fallen dead woody materials (10−21 kg/m2). The biomass of the forest floor (5−10 kg/m2) was similar to that of the tree slash (5−13 kg/m2), while the understory vegetation was a minor component (0.3−0.5 kg/m2). The quantity of slash and understory vegetation consumed by burning increased with the preburn mass of the same components. Forest floor consumption depended primarily on the preburn forest floor mass for windrow burns and on forest floor moisture content as well as preburn forest floor mass for broadcast burns. Fire severity generally did not have a strong influence on biomass consumption, although it did significantly influence forest floor consumption. There was a general trend, however, of increasing biomass consumption in broadcast burns with increasing fire severity. Windrow burning consumed more biomass than did broadcast burning under similar weather and fuel moisture conditions. Windrow burning resulted in uniformly high biomass consumption that was relatively independent of fuel moisture over the wide range of fuel moistures studied.