Location: Rangewide
Research Type: Literature Review
Forest Type: All

Critical habitat: Old forests. Reasons: predator avoidance (mature canopy), coarse woody debris (CWD), large diameter downfall, prey abundance ­ foraging success 21-119% greater in old-forest stands compared with successional forest.

Clearcuts: Less than 20% canopy cover is seldom used by martensuncut stands usually have around 50% canopy cover in winter. Successional forests after clearcutting (<45 yr after clear-cut) supported 0-33% of nearby uncut forest, depending on type of regeneration and amount of original forest removed. Where young forests used, marten subjected to high predation rates, were mostly young animals, and no reproduction.

Assumptions about habitat characteristics:

"(1) American martens will use forest with a canopy of at least 30% -- and prefer a canopy of 50-75%--in which more than half is provided by mature or old softwood trees.
(2) American martens prefer large-diameter downed wood for winter dens and as habitat for their major prey species.
(3) American martens require large-diameter standing old or dead trees for natal denning.
(4) American martens prefer forest with a complex understory or forest with fine-grained patches (gaps).
(5) In the short term, large cutovers (contiguous cuts over a 40-year period of 2 km2/year) eliminate American marten habitat. The more highly fragmented the mature forest becomes, the lower will be its carrying capacity for American martens.
(6) Carrying capacity of an even-aged mature conifer forest could be improved in thew short term by evenly dispersing a harvest of 20-25% of the stem basal area in 0.5 to 3.0 ha patches
(7) Selective logging, including using a shelterwood system, will not reduce a habitat's carrying capacity for American martens if removals are kept below 30% of the stem basal area every 50 years in boreal and montane forests, or every 100 years in temperate rain forests."

For boreal coniferous and mixed-wood forest, 20% of the forest should be mature and old at any time. In Ontario, approximately 600 km2 of old forest habitat is necessary to maintain MVP of 237 American marten.

Management Recommendations:
(1) For areas where martens occupy limited areas of old forest: maintain as much old forest as possible for as long as possible. Even aged management not an option. Program should have following components:
"an improved database that refines information for individual stands, including age information more specific than pooling 20- to 40-year age groups; some measure of decadence, site type, and predicted regeneration trajectory; a carefully designed integrated pest management program to protect against outbreak of insect pests; a harvesting strategy to remove only the most decadent stands in small patches and in a manner that maintains connectivity among uncut areas,retention of coarse woody debris during logging; GIS mapping of surrounding landscape to project future stand developmentand monitoring of American marten populations and their habitat."

(2) Where habitat supply not immediately critical: ecosystem supply analysisprovide enough ecosystem availability to provide adequate habitat over time.