Habitat suitability for marten of second-growth balsam fir forests in Newfoundland

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Abstract
The marten subspecies on the island of Newfoundland, Martes americana atrata, is threatened. Survey data suggest that most of the extant marten population lives in old uncut balsam fir (Abies balsamea) forests, but a very few live in adjacent 40- to 60-year-old second-growth stands of balsam fir. We compared habitat structure and composition and prey abundance in old forest and second-growth stands to test the hypotheses that either food abundance or habitat quality, or both, limit use of the 40- to 60-year-old forests by marten. Snowshoe hares (Lepus americana) were most abundant in 40-year-old forests and also occurred in old forests, but field voles (Microtus pennsylvanicus) were not found in second-growth stands. A multivariate discriminant model indicated that older, uncut forests contained more structure than younger forests at ground level, because there was more woody debris, more young balsam fir, less litter, more mosses, and more low shrubs. Canopy cover was similar in all forest types, and subnivean access did not differ among the three age-classes when snow was about 1 m deep. We suggest that marten did not use 40- or 60-year-old forest stands because of the lack of the meadow voles that form a necessary part of their diet. Meadow voles likely respond to ground-level forest structure in selecting habitat, and this structure is unavailable in young forests. We recommend a management strategy for marten that would preserve current old forests as long as possible and allow sufficient second-growth balsam fir forest to become old forest with the required characteristics to maintain a viable marten population.