Pontus M.F. Lindgren

STAND STRUCTURE AND SMALL MAMMALS IN YOUNG LODGEPOLE PINE FOREST: 10‐YEAR RESULTS AFTER THINNING

Management of forested landscapes for biological diversity is a major objective across North America. Perhaps the greatest potential to diversify future forests lies in the vast areas of young second-growth stands which may be managed silviculturally to accelerate ecosystem development. This study was designed to test the hypotheses that large-scale precommercial thinning, at ages 17–27 yr, to various stand densities would, over the 10-yr period since treatment, enhance: (1) productivity of lodgepole pine (Pinus contorta) crop trees, (2) stand structure attributes, and (3) species richness and diversity of forest floor small-mammal communities. Study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada, in three forest ecological zones. Each study area had three stands thinned to densities of ∼500 (low), ∼1000 (medium), and ∼2000 (high) stems/ha, with an unthinned juvenile pine and old-growth pine stand for comparison. Understory vegetation was measured ...

SMALL MAMMALS AND STAND STRUCTURE IN YOUNG PINE, SEED-TREE, AND OLD-GROWTH FOREST, SOUTHWEST CANADA

Alternative silvicultural systems to clearcutting are receiving considerable attention in Pacific Northwest forests of North America. Understanding the implications of these harvesting systems on stand structure and biodiversity through time is a fundamental aspect of forest ecosystem management. This study was designed to test the hypothesis that diversity of stand-structure attributes and forest floor small-mammal communities will increase from young pine to seed tree to old-growth forest. The study area was within mixed Douglas-fir (Pseudotsuga menziesii)–lodgepole pine (Pinus contorta) forests within the Montane Spruce biogeoclimatic zone near Summerland in south-central British Columbia, Canada. This retrospective study had three replicate stands each of 17-yr-old “young pine” (clear-cut harvested), “seed tree” composed of young pine with Douglas-fir seed trees, and uncut “old-growth” composed primarily of Douglas-fir and lodgepole pine. Stand-structure attributes (coniferous tree layers and understo...

Influence of conventional and chemical thinning on stand structure and diversity of plant and mammal communities in young lodgepole pine forest

Abstract Silvicultural practices that provide a wide variety of vegetative composition and structure (habitats) in young stands should help manage for biological diversity across forested landscapes. This study was designed to test the hypotheses that: (i) abundance and diversity of stand structure attributes (species diversity and structural diversity of herb, shrub and tree layers) and forest floor small mammal communities, and (ii) relative habitat use by large herbivores, will increase from unthinned to conventionally thinned to chemically thinned stands of young lodgepole pine (Pinus contorta) forest. Replicate study areas were located near Summerland, Kelowna and Williams Lake in south-central British Columbia, Canada. Each study area had three treatments: a conventionally thinned, a chemically thinned and an unthinned stand. Pre-commercial thinning was conducted in 1993. Coniferous stand structure and understory vegetation were measured prior to thinning in 1993 and 5 years later in 1998. Small mammal populations were sampled intensively from 1993 to 1998. Relative habitat use by large herbivores was sampled in 1998. Our results indicate that chemical thinning of young lodgepole pine stands produced an aggregated pattern of crop trees compared with stands subjected to conventional thinning. Diameter growth of crop trees in the chemically thinned stands was similar to that in the conventionally thinned, but also to that in unthinned stands. Although horizontal stratification (aggregates of trees) was enhanced, vertical stratification (structural diversity of vegetation) was less in the chemically than conventionally thinned stands. Abundance and diversity of understory vegetation and small mammal communities were generally unaffected by stand thinning in these particular installations. Relative habitat use by mule deer (Odocoileus hemionus) occurred in a gradient from highest in the conventionally thinned stand to lowest in the unthinned stand. Habitat use by snowshoe hares (Lepus americanus) tended to have the opposite trend. Moose (Alces alces) exhibited no difference in habitat use among stands. Thus, although there were few differences among treatment stands, chemical thinning could be used to develop an aggregated pattern of crop trees in pre-commercially thinned stands to maintain habitat for herbivores such as snowshoe hares and mule deer. Understory plant and forest floor small mammal communities would be maintained in these stands as well.

If we build habitat, will they come? Woody debris structures and conservation of forest mammals

Abstract Coarse woody debris (CWD) from forest harvesting and salvage wood from wildfire and insect outbreaks provide habitat for an array of forest-floor small mammal species and some of their mammalian predators. Because forest clear-cutting reduces abundance of many mammal species, strategic management of postharvest debris could help maintain abundance and diversity of forest mammals on harvested sites. We tested hypotheses that abundance and species diversity of forest-floor small mammals would be lower on conventional clear-cuts than in uncut forest; abundance and species diversity of forest-floor small mammals and relative activity and species richness of winter mammals would be higher on clear-cut sites with woody debris arranged in large piles or windrows than a dispersed treatment of debris. Small mammals were intensively livetrapped, and winter mammals snow-tracked, from 2007 to 2009 in replicated (n = 3) woody debris treatments of dispersed, piles, windrows, and uncut mature forest at 3 study areas in south-central British Columbia, Canada. We captured all 9 species of forest-floor small mammals. Compared with uncut forest, clear-cutting had no effect on mean total abundance of the small-mammal community, and species richness and diversity were either similar or higher. With respect to habitat preference, generalist species increased while specialist species declined. Habitat structures of large piles and windrows of woody debris on clear-cuts dramatically ameliorated these responses. On the basis of track counts, relative activity and species richness of winter mammals were enhanced by these structures, but the response was species specific. This is the 1st investigation showing significant increases in abundance and species diversity of forest-floor small mammals associated with constructed piles and windrows of postharvest woody debris on clear-cuts. Large-scale CWD structures as piles or windrows have clear conservation implications for mammals in commercial forest landscapes.

Mule deer–cattle interactions in managed coniferous forests during seasonal grazing periods in southern British Columbia, Canada

Abstract Context. In young forests of the Pacific North-west of North America, the potential impacts of domestic grazing by cattle (Bos taurus) on forest ecosystems and native ungulates such as mule deer (Odocoileus hemionus) are poorly understood. It is not clear how cattle and deer may interact in young forests used for summer range by both ungulates, and winter range used by deer, where pre-commercial thinning (PCT) and fertilisation enhance both timber and forage. Aims. To test the following two hypotheses: (H1) that PCT and repeated fertilisation of young lodgepole pine (Pinus contorta var. latifolia) stands would increase relative habitat use by cattle; and (H2) that increased use of forested range by cattle would result in decreased use by mule deer. Methods. Replicate study areas were located near Summerland, Kelowna, and Williams Lake in south-central British Columbia, Canada. Each study area had the following nine treatments: four pairs of stands thinned to densities of ∼250 (very low), ∼500 (low), ∼1000 (medium), and ∼2000 (high) stems ha–1 with one stand of each pair fertilised five times at 2-year intervals. Relative habitat use was measured by counting cowpies for cattle in summer and pellet groups for deer in summer and winter periods 1998–2003. Key results. Relative habitat use by cattle was significantly enhanced by fertiliser treatments and heavy thinning, supporting H1. Relative habitat use by deer during summer periods was not affected by stand density, but was significantly higher in fertilised than unfertilised stands, with no difference in winter months, thereby not supporting H2. Conclusions. Summer habitat use by mule deer appeared to be a function of forage opportunities and no significant correlations in relative habitat use between cattle and mule deer during the summer were detected. Negative correlations were better explained by the need for tree cover by deer during severe winter conditions than a negative response to cattle grazing. Implications. Domestic grazing by cattle may be compatible with native ungulates such as mule deer, at least in those forest sites that are managed intensively for timber production. Fertilisation may result in sufficient forage production in the understorey vegetation of these forest ecosystems, to compensate for cattle grazing that reduces the live forage biomass.

Silviculture and Wildlife: Snowshoe Hare Abundance across a Successional Sequence of Natural and Intensively Managed Forests

We tested the hypotheses H1 that relative habitat use by snowshoe hares (Lepus americanus) would have a bimodal distribution with the highest abundance in young lodgepole pine (Pinus contorta) stands (both managed and unmanaged), minimal numbers in mature forests, and moderate abundance in old-growth forests and H2 that habitat use would increase in response to enhanced stand attributes from PCT (precommercial thinning) and fertilization treatments. Habitat use was measured by counts of fecal pellets of hares from 1999 to 2003 in forest stands in south-central British Columbia, Canada. Our results did not support the bimodal distribution of hares among coniferous stands, such that old-growth stands, at least in our region, do not provide sufficient habitat for hare populations. High-density (5000 to 13000 stems/ha) unthinned young lodgepole pine stands provide optimum habitat for hares in terms of overstory and stand structure. Thinned and fertilized stands may also provide habitat, particularly at densities ≤1000 stems/ha, and over time as understory conifers develop. Managed stands provided habitat for hares at the same level as mature stands, at 6–10 years after PCT. Maintenance of a range of managed and unmanaged stands in a landscape mosaic would be ideal for integration of silvicultural and wildlife management goals.