Habitat selection and use in winter by moose in sub-boreal forests of north-central British Columbia, and relationships to forestry

A study of winter habitat selection and use by moose was conducted in a 11,300 km² area of north-central British Columbia from May 1971 to August 1973. The study area was located within the forested sub-boreal spruce biogeoclimatic zone, a zone that is receiving increased development, especially by forestry. Habitat selection and use was examined mainly be pellet group surveys and aerial transects. Wintering moose used partial cutovers and burns more than coniferous forests; deciduous forests and recent clearcuts were used least. Limited data suggested a similar pattern in summer. Winter use typically increased from near zero after a recent disturbance such as clearcutting, to a peak sometime between 10 and 25 years later, then declined to low levels during 25 and 90 years, and then apparently stabilized in the mature forest stage at slightly higher levels. On one intensively surveyed area, moose selected partial cutovers and creek bottoms even though these habitats comprised less than 6 percent of the area. Moose began concentrating on winter ranges at least by mid-November, reached a peak in November-January, and declined steadily thereafter. Food habits and diet were examined by rumen analysis, trailing and post-winter browse surveys. Moose had catholic diets but ate primarily deciduous browse for most of the year. Subalpine fir becomes important in late winter. Diet varied according to season and habitat. Preferred species typically were least common. Tagged twig transects revealed that moose frequently browsed plants more than once but rarely re-browsed a twig. The time of browsing varied by species and by habitat with most use recorded in January and in April. Levels of utilization were all less than 100 percent of the previous year's production. Utilization (weight-basis) ranged from 33 percent on red-osier dogwood to 3 percent on subalpine fir; and from trace amounts in an upland burn habitat to more than 40 percent in deciduous forest, partial cutover and river bottom habitats. Bedding .habits were examined in an attempt to define cover for moose. Moose choose upper slopes that faced south particularly when snow depths became restrictive (> 80 cm). Moose tended to select larger than average trees and to bed on the southerly sides of them. Selection of bed sites varied with snow depth. As snow became deeper, moose bedded closer to larger trees in the denser canopied parts of forest stands. Moose showed greater selection for protected sites as winter conditions became more severe. Secondary seral succession was examined with respect to several attributes for mesic environments on the two commonest substrates, glacial till and lacustrine deposits. Floristics of seral stages from 1-200 years revealed that on lacustrine soils, vegetation was more, diverse and the deciduous phase was prolonged. Species diversity declined around year 25 on till but not on lacustrine. Several major changes occurred in the tree layer: first, a deciduous tree layer developed especially on lacustrine soils; second, after 25 years on till (45 years or more on lacustrine), lodgepole pine became most abundant; third, pine was gradually replaced by white spruce after 150-200 years or more; fourth, subalpine fir would probably become the dominant tree species in the absence of fire. Understory phytomass, though contributing little to the mature forest mass, increased dramatically to peaks early in succession and then remained low. Approximate net primary production of the understory on till was greatest at age 11 with 133 g/m²/yr produced and least at age 39 with 18 g/m²/yr produced. Understory production in the mature forest was and estimated 27 g/m²/yr. The shrubs contributed 70 percent, 26 percent, 44 percent, and 26 percent of annual production at ages 1, 11, 39, and 195 years, post-disturbance. Crude protein and lignin values were determined for 10 species (eight shrubs, one conifer, one lichen) for an annual cycle. Crude protein averaged 7 percent and lignin, 9.8 percent. Crude protein increased abruptly from steady winter values to peaks of 10-15 percent in June-July and then returned to low levels by October. Leaf protein was higher than, and predictable from, stem levels. Crude protein varied by-species, sometimes by substrate and rarely by habitat-type, at least for the species analyzed. The lichen, lungwort, retained a high protein value of approximately 11 percent throughout the year. Lignin levels varied seasonally, though less dramatically than crude protein. Levels were affected by species, substrate and age of seral stage. Protein levels were similar to those reported in the literature. Factors influencing crude protein were difficult to disentangle due to confounding. Winter climate was studied with respect to differences in snow features between habitats. Moose moved into winter ranges before snow depths were limiting. This indicates snow acts to trigger migration. On winter ranges, moose also moved into forested habitats in mid-winter (January) when snow depths approached 80 cm. Snow depths and densities varied between habitats. Snow cover was more variable in partially logged cutovers than in the open or forested stands. The climate of forest, ecotone and adjacent open areas were documented. Compared to adjacent open areas, the forest had higher relative humidity, less wind, more moderate temperatures and approximately 50 percent of the snow depth. The transition zone from open to forest climates appeared to be relatively narrow, less than 50 m. The relationship between carrying capacity, habitat selection and home range are discussed with reference to moose and management of their habitat. Management recommendations and suggestions for future research are provided.

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