Small-mammal community composition, microhabitat selection, and
dispersal of mycorrhizal fungal spores were studied in southwestern
Oregon. Sampled habitats exhibited structural variation resulting
from silvicultural practices.
In 1981, the effect of clearcut treatment on these phenomena was
evaluated. In 1982, the effect of forest structure was studied.
Discriminant function analysis (DFA) and principal component
analysis (PCA) were used to distinguish and characterize clearcut,
edge, and forest habitats of study sites. Microhabitat preferences
of small-mammal species were examined using DFA. For each habitat
in every site, species diversities and related community parameters
were calculated. Relationships among habitat structure,
microhabitat preferences, and community composition parameters were
examined using partial correlation analysis. Distances moved by
small mammals between the clearcuts and forests were determined for
common species. Spore abundances in fecal pellets were calculated
for small-mammal species that moved among the three habitats.
In 1981, 1273 individuals of 11 species were captured. Deer
mice (Peromyscus maniculatus) and chipmunks (Tamias spp.) comprised
81.6 percent of all trapped animals. As degree of forest structure
increased, the relative abundances of deer mice decreased and those
of chipmunks and red-backed voles increased. Thus, small-mammal
community composition changed with increasing habitat complexity.
Only deer mice and chipmunks moved among all habitats, and no
consistent effect of clearcut treatment was observed on movements of
either species. Chipmunks excreted more kinds and greater
quantities of fungal spores than deer mice.
In 1982, 1287 individuals of seven small-mammal species were
captured; golden-mantled ground squirrels (Spermophilus lateralis),
deer mice, and yellow pine chipmunks (Tamias amoenus) were the most
numerous. Relative abundances of small-mammal species varied with
overall habitat complexity. As degree of forest structure
increased, the relative proportions of forest specialists influenced
small-mammal community composition.
Ground squirrels, deer mice, and chipmunks moved among the three
habitats. Differences in movements between habitats among these
species reflected habitat affinities. Abundance of spores in feces
was highest for Siskiyou chipmunks (Tamias siskiyou) followed by
ground squirrels, deer mice, and yellow pine chipmunks. For all
small-mammal species combined, the greatest spore abundance was
recorded for samples from the least disturbed forest.
Small-mammal and fungal communities respond to habitat
alteration. Principal small-mammal mycophagists and fungi occur in
greater numbers in minimally disturbed forests and untreated
clearcuts. To maximize inocula availability in disturbed sites,
adjacent forests and the understory in clearcuts should be left
undisturbed
