This is an excellent overview of the state of knowledge regarding the ecology and conservation status of the marten. Some notable excerpts follow.

Natural History
“The American marten is broadly distributed. It extends from the spruce-fir forests of northern New Mexico to the northern limit of trees in arctic Alaska and Canada, and from the southern Sierra Nevadas of California to Newfoundland Island... in the western contiguous United States, its distribution is limited to mountain ranges that provide preferred habitat.” (p. 7)

“American martens... associate closely with late-successional stands of mesic conifers, especially those with complex physical structure near the ground...” (p. 7)

“The reproductive rates of martens are low, and longevity is high, by mammalian standards. This suggests that, for a 1-kg mammal, martens are slow to recover from population-level impacts.” (p. 16)

“In virtually all cases involving standing trees, logs, and snags, dens were found in large structures that are characteristic of late-successional forests... Given the importance of natal dens to recruitment, the availability of structurally complex sites could have important implications for conservation.” (p. 17)

“... studies have generally shown that martens make little absolute or relative use of clearcuts for several decades and that marten populations decline after clearcut logging... studies showed consistent use/availability ratios <1 in shrub, sapling, and pole stages. Only when succession reached the “mature” stage did use/availability ratios begin to exceed one, and only “overmature” stands were constantly preferred.” (p. 24)

“The mechanisms by which martens are impacted by timber cutting are the removal of overhead cover, the removal of large-diameter coarse woody debris, and, in the case of clearcutting, the conversion of mesic sites to xeric sites, with associated changes in prey communities...” (p. 25)

“Coarse woody debris, especially in the form of large-diameter tree boles, can address many of the needs that martens have for physical structure: predator avoidance, access to subnivean spaces..., and thermal protection...” (p. 25)

“... Robinson (1953) found that martens avoided traveling >23 m from forest edges in Colorado... [five other studies] have reported complete or partial avoidance of nonforested habitats. The size of openings that martens have been observed to cross have varied from 10 m ... to 40 m... to 100 m... In most cases, these are the largest openings that the authors observed to be crossed during their respective studies.” (p. 26)

Home ranges were recorded as large as 15.7 km2 (Mech and Rogers 1977)...
“... home ranges of American martens are 3-4 times larger than predicted for a 1-kg terrestrial carnivoran, and about 30 times that predicted for an herbivorous mammal of that size... home ranges in clearcut areas [have been reported at] 1.5-3.1 times the size of those in uncut areas.” (p. 27)

Distribution and Taxonomy
“On balance, the American marten has a smaller distribution now than in presettlement historical times (Gibilsco 1994); the total area of its geographic range appears similar to early this century, when it was at its historical low.” (p. 10)

Population Insularity
“... biologists are generally agreed that over 5 kilometers of treeless land below the lower elevational limit of trees acts as a complete barrier to dispersal (Gibilisco 1994; Hawley and Newby 1957).” (p. 12)

Trapping
“Early season trapping tends to selectively remove juveniles, but seasons that extend into late winter or spring begin to remove more adults. Likewise, early trapping tends to selectively remove males, but trapping after the onset of gestation shifts toward selective removal of females.” p. 15)

“For over 40 years, researchers have emphasized the importance of refugia to the conservation of American martens.” (p. 26)

Conservation Status (p. 29)

“1. In the western United States, the marten has undergone major reductions in distribution... The reduction and fragmentation of the geographic range of martens has resulted primarily from the loss of habitat due to timber cutting...
4. Several marten populations are known or hypothesized to have been isolated by human-caused habitat change. The genetic and stochastic processes that predispose small populations to extinction likely are acting on these remnants...
5. The marten is predisposed by several attributes to impacts from human activities. These attributes include its habitat specialization for mesic, structurally complex forests; its low population densities; its low reproductive rate for an animal its size; and its vulnerability to trapping...
6. ... trapping may adversely affect some marten populations and may have contributed to or hastened local extinctions, especially where habitat quality was poor...
7. Clearcutting, the most common timer harvesting practice in the northwestern United States in the last 20 years, is generally deleterious to marten populations. Regenerating clearcuts have little or no value as marten habitat for several decades... consistent preference is not shown by martens until stands reach the “mature” or “overmature” stage.
8. Changes in patterns of distribution and abundance of martens indicate that this species is not secure throughout its range. In areas where populations appear to have been isolated by human actions, or where already isolated populations have had the carrying capacity of the habitat reduced, immediate measures to ensure persistence appear prudent...”