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The American marten (Martes americana) is associated with large tracts of relatively undisturbed, mature coniferous forests. I examined coarse woody debris (CWO) structure and small mammal abundance with respect to forest age and stem structure within second-growth forests, in comparison with old-growth stands in western Newfoundland. Results suggest that a critical change in marten habitat quality may occur at stand senescence, due to decreased tree competition, more complex subcanopy structure, and increased meadow vole (Microtus pennsylvanicus) abundance. Analysis of stem structure within a chronosequence of 19 second-growth stands indicated high intertree competition, with dense canopy closure and active self-thinning, until stand senescence at 80 years. Old-growth stands were less dense, offering more canopy openings. CWD volume observed within the chronosequence demonstrated the typical U-shaped temporal relationship observed in other forested systems. Lowest CWD volumes were observed within semimature to mature second growth. Highest levels of both CWD volume and structural complexity corresponded with stand senescence and old growth. Small mammals were sampled within immature, semimature, mature, and silviculturally overmature coniferous stands in western Newfoundland during 1993 and 1994. Meadow voles were most abundant within overmature stands (P Results from this study suggest that the critical elements of marten foraging habitat currently are found within a senescent forest stand structure. Further review of the literature and Newfoundland harvest records indicated that anthropogenic disturbance transformed a historically heterogeneous forested landscape into a more contiguous, even-aged, second-growth environment. Using the stand density management diagram, I designed a silvicultural approach to marten habitat management that simulates the structure of older forests within younger stages of forest development.