Search Results (4)

We report a landscape-scale natural experiment that followed the abundance and demography of forest-floor small mammals and the activity of small mustelids over a 4-year period of an extreme heat wave and abundant coniferous cone crops. Deer mice (Peromyscus maniculatus) and southern red-backed voles (Myodes gapperi) are major species in the coniferous forest-floor small mammal community near Summerland in southern British Columbia, Canada. Their major mammalian predators include the short-tailed weasel (Mustela richardsonii), long-tailed weasel (Neogale frenata), and American marten (Martes americana). We evaluated three hypotheses (H) that may explain the changes in these mammals from 2021 to 2024: (H₁) that large coniferous cone crops in 2022 would have generated high populations of forest-floor small mammals in 2023 owing to enhanced reproductive output and overwinter survival; (H₂) that increased activity of mustelids would have followed population increases, resulting in the decline of small mammal prey in 2024; and (H₃) that the widespread occurrence of cone crops in 2022 would also have elicited the same mammalian responses in 2023 at a second study area (Golden, BC) 276 km and three mountain ranges from Summerland. During the summer periods of each year, small mammal populations were monitored by intensive live-trapping, and mustelid presence was measured via an index of activity based on live traps, fecal scats, and predation events. The mean abundance and reproductive performance of the P. maniculatus and M. gapperi populations increased in response to the coniferous seedfall, thereby supporting H₁. The activity of small mustelids responded positively to increased numbers of small mammal prey and potentially acted in a regulatory and top–down function in these communities, and hence partially support H₂. Similar responses at Summerland and Golden indicated that this seedfall event and changes in the mammalian community occurred at a landscape-scale, thereby providing partial support for H₃. Potential differential effects of large seed crops on consumers did not affect the mean abundance patterns for P. maniculatus but apparently reduced this metric for M. gapperi. Heat waves, induced by anthropogenic climate change, may alter the frequency of coniferous masting events, and their effects may temporarily change the number and species of mammalian seed consumers and their predators. Full article

Responses of forest-floor small mammals to clearcutting are species-specific with generalists occupying a range of habitats, and specialists persisting on clearcuts for variable periods. We investigated the responses in abundance and species composition of small mammal communities to cumulative clearcutting of coniferous forests on a landscape that had four independent clearcutting events (Periods 1 to 4) over a 42-year interval from 1979 to 2020 in south-central British Columbia, Canada. We ask if the small mammal communities have changed significantly over these decades owing to removal of old-growth forest by clearcut harvesting. Hypotheses (H) predicted that the small mammal community would (H₁) increase in abundance, species richness, and diversity on new clearcuts owing to the availability of early seral post-harvest habitats from cumulative clearcutting; and (H₂) have higher mean abundance, species richness, and species diversity in clearcut than uncut forest sites, owing to availability of vegetative food and cover. A third hypothesis (H₃) predicted that abundance of (i) early seral vegetation (herbs and shrubs) and (ii) small mammal populations, will be greater in ungrazed clearcut sites than in those grazed by cattle (Bos taurus). Mean total numbers of small mammals on new clearcuts declined in Periods 3 and 4, and hence did not support the abundance part of H₁. Much of this decline was owing to low numbers of the long-tailed vole (Microtus longicaudus) and meadow vole (M. pennsylvanicus). Two generalist species: the deer mouse (Peromyscus maniculatus) and northwestern chipmunk (Neotamias amoenus), contributed to high mean species richness and diversity in Periods 2 and 3 before these metrics declined in Period 4, and hence partly supported H₁. The similarity in mean total numbers of small mammals in Periods 2 to 4 did not support the abundance prediction of H₂ that total numbers would be higher in clearcut than uncut forest sites. Higher mean species richness (Periods 2 and 3) and diversity (Period 3) measurements on clearcut than forest sites, particularly in the early post-harvest years, did support these parts of H₂. The vegetation part (i) of H₃ was not supported for herbaceous plants but it was for shrubs. The small mammal part (ii) of H₃ that populations would be higher in ungrazed than grazed clearcut sites was supported for abundance but not for species richness or diversity. The decline and near disappearance of both species of Microtus was possibly related to the reduction in plant community abundance and structure from grazing (at least for shrubs) and potentially from drought effects associated with climate change. Loss of microtines from these early seral ecosystems may have profound negative effects on various ecological functions and predator communities. Full article

Coarse woody debris on the forest floor contributes to maintenance of forest biodiversity and long-term ecosystem productivity. Down wood is often dispersed over harvested sites during logging activities, thereby leaving piles of postharvest debris as “excess” material at landings and roadsides. These wood residues may be burned in most jurisdictions in North America to reduce a perceived fire hazard. The fire hazard debate needs to acknowledge the documented benefits of woody debris retention while striking a balance among biodiversity, bioenergy, and alternative uses for debris, while reducing ignitions by humans. The burning of excess woody debris also creates smoke, causes the release of greenhouse gas (GHG) emissions, and creates human health issues, particularly for vulnerable individuals. The relationship of wildfire smoke to human health problems is well documented. However, there is no scientific evidence showing that postharvest debris piles are ignition points for forest fires, other than those caused by humans. Wood residues from forest harvesting or natural disturbance wood from wildfire and insect outbreaks may be used as renewable biomass “feedstocks” that could help improve energy supplies and reduce GHG emissions. If not marketable, the management of postharvest debris should seek alternative outlets that do not dispose of debris by burning, but still meet fire hazard abatement requirements. The construction of woody debris structures (e.g., piles and windrows) built at the time of forest harvesting and log processing, or later at the site preparation stages, has positive benefits for wildlife habitat and forest biodiversity. A windrow or series of piles may connect patches and reserves of mature forest and riparian areas on clearcut openings. Piles and windrows have consistently provided habitat on new clearcuts for southern red-backed voles (Myodes gapperi) and Microtus voles, as well as a host of other forest-floor small mammal species, at least up to 12 years postconstruction. Woody debris provides important habitat for foraging and cover attributes for marten (Martes americana), weasels (Mustela spp.), and other furbearers. A list of “What to do?” and “When and Where?” with options for construction of woody debris habitats: poorest, good, better, and best are given. In the cases where fire risk from humans is minimized and there are no marketable wood products, eight alternative management scenarios for postharvest woody debris are provided. These include: (1) piles for wildlife habitat; (2) distribution of debris in partial cut forests; (3) machinery to break up and crush debris; (4) protection of riparian zones with barriers for cattle; (5) construction of range fencing; (6) reclamation of landings and skid-trails; (7) soil fertility and reduction in weed competition and drought for planted conifers; and (8) slope stabilization and revegetation. Advantages and disadvantages (if known) are given for each alternative. A flow chart for the fate of excess postharvest woody debris with respect to fire hazard abatement and markets or nonmarkets is given. Full article

There is a demand for more progressive restoration directives to regenerate forest ecosystems impacted by harvesting, wildfire, insect outbreaks, and mineral resource extraction. Forest restoration may take many decades and even centuries without active silvicultural intervention to grow large trees that provide suitable habitat for various wildlife species. We tested the hypotheses (H) that, compared with unmanaged (unthinned and old-growth) stands, large-scale precommercial thinning (heavy thinning to <500 stems/ha) of young lodgepole pine (Pinus contorta var. latifolia), at 20–25 years post-treatment, would enhance: (H₁) the architecture of large overstory trees (e.g., diameter, height, and crown dimensions); (H₂) mean (i) total abundance and species diversity of forest-floor small mammals, (ii) abundance of tree squirrels; and (H₃) relative habitat use by mule deer (Odocoileus hemionus). There were three levels of thinning with mean densities of crop trees/ha: 353 (low), 712 (medium) and 1288 (high), an unthinned, and old-growth stand replicated at three areas in south-central British Columbia, Canada. Mammal abundance and habitat use were measured during the period 2013 to 2015. Mean diameter of crop trees was significantly different among stands with the low-density, medium-density, and old-growth stands having diameters larger than the high-density and unthinned stands. Mean height of crop trees was highest in the old-growth stands. Mean crown volume of crop trees was significantly different among stands with the low-density stands 2.1 to 5.8 times higher than the high-density, unthinned, and old-growth stands, and hence partial support for H₁. Mean total abundance of forest-floor small mammals was significantly different among stands with the low-density and old-growth stands 1.9 to 2.4 times higher than the other three treatment stands. Mean abundances per stand of the red squirrel (Tamiasciurus hudsonicus) (range of 4.8 to 12.0) and the northern flying squirrel (Glaucomys sabrinus) (range of 3.2 to 4.3) were similar among stands. Mean relative habitat use by mule deer was similar among stands, but variable with counts of pellet-groups/ha in the thinned stands were 3.8 to 4.2 and 2.1 to 2.3 times higher than the unthinned and old-growth stands, respectively. Thus, mean total abundance of forest-floor small mammals of H₂ was supported, but species diversity and abundance of tree squirrels was not. Enhanced relative habitat use by mule deer (H₃) was not supported. To our knowledge, this is the first concurrent measurement of several mammal species in heavily thinned, unthinned, and old-growth forest across three replicate study areas at 20–25 years post-treatment. Although not all mammal responses were significant, there was a strong indication that restored forests via heavy thinning (<500 trees/ha) produced large overstory trees (at least for diameter and crown dimensions) in stands 33 to 42 years old. Comparable old-growth stands, albeit with crop trees of greater height and merchantable volume, ranged from 120 to 167 years of age. Restored forests with large trees capable of supporting at least these mammal species may be achieved in decades rather than centuries. Full article