摘要 : Timber harvesting residues have typically been burned within coniferous forest areas of the eastern Cascade Mountains of Washington State, USA. Concerns about air pollution and quantities of coarse woody debris have generated inte... 展开 Timber harvesting residues have typically been burned within coniferous forest areas of the eastern Cascade Mountains of Washington State, USA. Concerns about air pollution and quantities of coarse woody debris have generated interest in alternativeresidue treatments that will clear areas for planting and still reduce fire hazard. A total of 6 residue treatments were compared (3 slash treatments where residues were burned - spring broadcast burning, fall broadcast burning, and piling and burning;and 3 treatments where residues were not burned - clearing, chopping, and pulling unmerchantable material), along with no slash treatment to determine the effects of alternative approaches on soils and seedlings. Slash-treatment effects on soil bulk density and temperature, air temperature, and seedling growth and survival were examined at 4 different sites in the eastern Cascade Mountains. Results show that seedling performance was best with spring broadcast burning across all sites over 5 yr of growth. Average height growth of Douglas fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta) over 5 yr was 90 cm in the spring broadcast burn, and 75, 72, 71, 71, 66 and 61 cm for no slash treatment, piling and burning, pulling unmerchantable material, chopping, fall broadcast burn, and clearing, respectively. Seedling height growth may be related to soil temperatures that are closer to optimal for root and shoot growth when large quantities of slash were not insulating the soil. Soil bulk densitydid not appear to affect seedling growth (bulk density ranged from 0.7 to 1.15 g cm-3). None of the slash treatments that avoided burning increased growth relative to no slash treatment, and some may have adversely affected survival. If slash burning cannot be used to reduce quantities of timber harvesting residues, then leaving slash untreated appears to be the best alternative for seedling growth. The second (following) paper (Scherer et al., pp. 35-50) reports the effect of residue treatment on understorey vegetation. 收起