Rodent Occurrence, Habitat Disturbance, and Seed Fall in a Larch‐Fir Forest

Abstract

Small—mammal population changes were measured for 5 yr (1970—1974) by live trapping on broadcast burned western larch (Larix occidentalis)/Douglas—fir (Pseudotsuga menzielsii) clear—cuts and in uncut timber on a north and a south slope in western Montana. Four species comprised 96% of the 1324 animals caught: deer mice (Peromyscus maniculatus) 42%, red—backed voles (Clethrionomys gapperi) 27%, red—tailed chipmunks (Eutamias ruficaudus) 22%, and long—tailed voles (Microtus longicaudus) 5%. Deer mice and chipmunks were common on clear—cut and timber plots. The red—backed vole and long—tailed voles were associated with moist sites but showed local allopatry. The red—backed voles were present only under tree canopy and the long—tailed vole was found only in absence of tree canopy. A hard burn effect was to eliminate most of the organic mantle and all small mammals except deer mice, who existed as the single species for 2 yr, and as 80—90% of numbers for 5 postburn yr. A light burn which left duff intact was associated with retention of species diversity and a low initial postburn (2 yr) mammal population, followed by the largest increases. Numbers of deer mice varied inversely with numbers of red—backed voles in the timber. Deer mice increased sharply on all plots the first fall after a heavy conifer seed crop, an occurrence reported by other workers. From these pattern observations it is theorized that red—backed voles may dominate deer mice, but a heavy seed crop can temporarily enhance competitive standing of deer mice. An open, xeric, pioneering situation (hard burn) was conducive to persistently high deer mouse populations. The most obvious habitat feature associated with an inverse spatial relationship between the two voles was tree canopy. The long—tailed vole may be further discriminated against by drier habitats. Clear—cutting appeared to be the principal determinant of total population size, but burn intensity seemed to influence species composition.

Forecasting vole population outbreaks in forest plantations: The rise and fall of a major mammalian pest

“…Most Microtus species respond favorably to moisture-bearing sites with enhanced growth of herbaceous plants (Getz, 1985). Long-tailed voles were captured mainly on seepage sites in north-aspect burned units in Montana (Halvorson, 1982). Similar results were recorded for creeping voles (M. oregoni) in Oregon (Gashwiler, 1970;Hooven, 1973).…”

“…Clearcut sites in forests have created variablequality habitats for long-tailed voles in Montana (Halvorson, 1982), Alaska (Van Horne, 1982), and British Columbia (B.C.) (Sullivan et al, 1999;Sullivan and Sullivan, 2001).…”

Population estimation with sparse data: the role of estimators versus indices revisited

“…We believe that index-based studies have provided a great deal of reliable information concerning small-mammal habitat use and responses to management. For instance, in the Rocky Mountain region of the United States, southern redbacked voles (Clethrionomys gapperi) prefer mature and lateseral forests to recent clearcuts and young forests (Ramirez and Hornocker 1981;Halvorson 1982;Scrivner and Smith 1984;Medin 1986;Hayward and Hayward 1995). This research has not only proved to be repeatable, but the outcome, that clear-cutting reduces densities of red-backed voles, has repeatedly proved to be true (for a review see Pearson 1999).…”

Fire ecology of western Montana forest habitat types

“…The bird depends on medium to large fire-created forest openings with shrubgrass-forb vegetation for breeding adjacent to dense foliage conifers for roosting and hooting. Table 4-Probable effects of fire on some western Montana mammals, reptiles, and amphibians (major sources : Allen 1983;Bendell 1974;Bernard and Brown 1977;Black and Tabor 1977;Halvorson 1981Halvorson , 1982Hobbs and Spowart 1984;Kelsall and others 1977;Lyon and others 1978;Maser andothers 1981: Ream 1981;Ream and Gruell 1980;Thomas 1979;USDA Forest Service 1978;Verner and Bass 1980;Wright and Bailey 1982). Classification, scientific names, and common names according to USDA Forest Service (1978 Prefers streamsides, marshes, and bogs, but also occurs in moist soil; mat of ground vegetation or debris for cover.…”