5th Symposium on Fire and Forest Meteorology and the 2nd International Wildland Fire Ecology and Fire Management Congress

Monday, 17 November 2003
Short-term responses in aspen regeneration for wildlife habitat in interior Alaska
Thomas F. Paragi, Alaska Department of Fish and Game, Fairbanks, AK; and D. A. Haggstrom
Fire suppression and limited timber markets are hindering maintenance of early-successional broadleaf forest for wildlife habitat near settlements in interior Alaska. During 1999-2002 we evaluated the efficacy of felling and shearblading (with and without debris removal) and prescribed fire to regenerate quaking aspen (Populus tremuloides). Sprouting in aspen is positively correlated to surrounding tree mortality because root suckering is suppressed by apical dominance. Our objective in treating mature aspen (70-80 yrs. old and 1,500-2,000 trees/ha) was to produce >30,000 stems/ha after two growing seasons to initially produce escape cover for ruffed grouse (Bonasa umbellus) broods and forage for moose (Alces alces) and snowshoe hares (Lepus americanus).

Prescribed burns utilizing natural debris were hand-fired for $790/ha just prior to leaf emergence in mid-May to top-kill aspen by scorching the lower bole. Treatment sites were 2-12 ha and south-facing with loess soils. Sprouting response ranged from 40,900 stems/ha (95% CI: 31,680-50,120) to 233,000 (169,350-296,650) and was patchy within four of six sites. Weather conditions during firing (relative humidity and wind vector) and topography (slope and aspect) induced within-site variation in fire intensity that affected tree mortality and spatial variation in sprouting response. The sprouting objective was often met on individual plots (>15 stems per 5m2, n=95) when fire killed >40% of trees within 10 m; topographic conditions for successful fire behavior included slope >10o, southerly aspect, and adjacent openings in the forest to allow wind at ground level.

Mechanical treatments on 4-11 ha sites were conducted during the dormant period (late August-early April) to maximize resources for root sprouting at four management areas of differing productivity. Felling by chain saw on six hilly loess sites cost $570/ha and produced 34,800-89,800 stems/ha, whereas dozer shearblading on four floodplain sites cost $185/ha and produced 24,200-64,800 stems/ha. Within-site variability in sprouting response was lower for mechanical treatments than for burns because 100% tree mortality was ensured.

Debris shading can reduce soil temperature and sprouting response, so we tested the effect of clearing debris at a hilly felling site on loess ($1,850/ha) and at a shearblading site on flat glacial outwash ($310/ha). Soil temperature exceeded 15oC only at a debris-free section of the loess site (west-southwest aspect, 11-19o slope). Sprouting response on loess was higher on cleared sections (142,200 stems/ha [95% CI: 91,950-192,450]) than on sections where sheared debris remained as it was felled (49,800 [33,080-66,520]). Sprouting response on glacial outwash was not significantly higher on cleared sections whether moss ground cover was scraped off (124,400 [81,520-167,280]) or moss remained (98,000 [59,860-136,140]) relative to sections where debris remained as it fell after shearing (60,400 [29,310-91,490]).

Mechanical treatments were 25-75% of the cost of prescribed fire but produced debris extending >1 m above ground in places that may hinder access by grouse broods and moose. Snow track surveys indicated that felling debris may also attract terrestrial predators of grouse broods, such as weasels (Mustela spp.) and marten (Martes americana).

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