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Fire and Woodland Caribou in Southeastern Manitoba

James A. Schaefer and William O. Pruitt, Jr.
Wildlife Monographs
No. 116, Fire and Woodland Caribou in Southeastern Manitoba (Apr., 1991), pp. 3-39
Published by: Wiley on behalf of the Wildlife Society
Stable URL: http://www.jstor.org/stable/3830581
Page Count: 37
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Fire and Woodland Caribou in Southeastern Manitoba
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Abstract

The effects of fire on the Aikens Lake population of woodland caribou (Rangifer tarandus caribou) were studied over a 2-year period. Quantity, quality, and accessibility of forages were determined in recently-burned (5-yr-old) habitats and compared to those in intermediate (37 yrs) and old-growth (90-160 yrs) stands. These measures were correlated with patterns of habitat use by Aikens caribou over 2 winters. Forage productivity was determined by harvesting the current growth of vascular plants and standing crop of arboreal and terrestrial lichens. Quality of forage was inferred from the content of acid detergent fiber and published digestibility studies of Rangifer. Accessibility of forage was estimated from the Värriö Snow Index, including hardness and thickness of snow cover, and from the intersection frequency of windfallen trees. Principal components analysis revealed that original floristic distinctions between jack pine (Pinus banksiana) and mixed forest communities persisted after fire. Compared to old-growth stands (90 yrs), most burned upland habitats exhibited enhanced productivity of summer forages but a decline in quality and accessibility of winter forages. This deterioration of winter habitat for caribou resulted from the loss of lichens (Cladina spp.) in the predominant jack pine communities, the increase in both thickness and hardness of snow cover, and the accumulation of deadfalls. The oldest stands (160 yrs) showed the lowest forage productivity, including lichens, but had the most favorable nival conditions. Caribou winter travel and feeding were significantly skewed towards use of lakes, old-growth uplands and bogs, and away from burned uplands. In both winters of study, Aikens caribou continued to exploit the remnant lichen supply in old-growth bogs and crown-burned habitats within the limits of the 5-year-old burn. In late winter, however, caribou shifted their activity entirely outside the recent burn in favour of stands ≥55 years old. The heightened accumulations of snow and deadfalls are implicated in this late-winter range abandonment. The winter range of the population, 5.5 years after fire, was mutually exclusive with its prefire range. Taiga in southeastern Manitoba is not suitable for woodland caribou in its recently-burned and intermediate stages (up to 50 yrs following fire). Yet fire may be necessary to maintain optimal, long-term lichen resources. Due to the remnant lichen supply in burned areas and the delay in the accumulation of windfallen trees, the short-term detriments of fire may not be fully realized until 5 years or more after burning. Woodland caribou adapt to these short-term effects by abandoning their range. Local fire history-in particular, proximity to alternative, lichen-rich stands-must be considered in the management of woodland caribou habitat.

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