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Small Mammals in Managed, Naturally Young, and Old-Growth Forests
Ecological Applications
Abstract
Forest managers in the Pacific Northwest are faced with new challenges of providing for all wildlife in managed forests. Our objective was to elucidate the factors governing the composition and biomass of forest floor mammal communities that are amenable to management. We sampled small mammal communities in forests of various management histories on the Olympic Peninsula and contrasted our results with those of other large studies in the Pacific Northwest. Forest floor mammal communities in forests >35 yr old in the Western Hemlock Zone of Washington and Oregon are composed of 5-8 characteristic species. These include Sorex trowbridgii (numerically the most dominant); one species each of Clethrionomys, the Sorex vagrans complex, and Peromyscus; and Neurotrichus gibbsii. Species composition changes from south to north, and the communities on the Olympic Peninsula contain two or three additional species compared to communities to the south. Communities in naturally regenerated and clearcutting regenerated (managed) young forests are similar in composition to those in old growth, old growth, however, supports 1.5 times more individuals and biomass than managed forest. Community diversity seems related to the south-north moisture-temperature gradient that is reflected in increased diversity of canopy conifers, development of forest floor litter layers, accumulation of coarse woody debris, and abundance of herbs, deciduous shrubs, and shade-tolerant seedlings (as opposed to understories dominated by evergreen shrubs). Previous work found few habitat variables that were good predictors of species abundance in natural young and old-growth stands. Naturally regenerated young stands had higher levels of coarse woody debris than old growth. Managed stands had much lower abundance of coarse woody debris and tall shrubs than old growth. Understory vegetation (herbs and shrubs) and coarse woody debris accounted for a major part of the variation in abundance of six of eight species in managed stands, but only two species in old growth. Management of Western Hemlock Zone forest for conservation of biodiversity and restoration of old-growth conditions should concentrate on providing multispecies canopies, coarse woody debris, and well-developed understories.
... At the same time, small mammals are prey to a variety of birds, reptiles, and mammals (Chubbs & Trimper, 1998;Dawson & Bortolotti, 2000;Shao et al., 2019;Zhao et al., 2020). Understanding the effect of forest compositional change on the diversity and community structure of small mammals is crucial for forest management and biodiversity conservation (Carey & Johnson, 1995). ...
... At the site scale, in contrast to the landscape scale results, TD, FD, and PD were highest in the primary forests and lowest in the plantation forests during all three seasons. This result suggests that although small mammals can survive in the three forest types, the primary forests were preferred likely due to more stable forest structure and higher habitat heterogeneity (Carey & Johnson, 1995;Gray et al., 2019;Rebelo et al., 2019). In addition, the secondary forests were characterized by a natural plant community recovered from the deforested primary forest, and their forest structure and habitat heterogeneity will gradually approach that of the primary forest as stand age increases. ...
Secondary and plantation forests are the main alternative forests remaining after the deforestation of primary forests. Understanding the conservation value of secondary and plantation forests is important for biological conservation. To explore the impact of forest conversion on biodiversity, we compared multiple diversity metrics (taxonomic, phylogenetic, and functional diversity) and community structure of small mammals in the primary, secondary, and plantation forests in Mt. Liangshan, Sichuan Province, China. Three field surveys were conducted in each of the three forest types to characterize local small mammal assemblages from 2017 to 2020. We found that the taxonomic, phylogenetic, and functional diversity of small mammals in the three forest types were similar at the landscape scale, while all diversity metrics were lowest in the plantation forest and highest in the primary forests at the site scale. The community structure analysis showed that habitat filtering was the dominant process driving the assembly of small mammal communities across the three forest types, and there was no statistically significant difference in small mammal community structure among the three forest types. Our results indicated that secondary and plantation forests in the nature reserves, adjacent to the primary forest and exposed to little human disturbance, also can provide important habitats for small mammals.
... Keywords Squirrels · Knowledge gaps · Scopus · PRISMA · Temporal · Spatial · Funding being hunted by large predators (Carey and Johnson 1995). Asia has the largest diversity of sciurids followed by Africa (Koprowski and Nandini 2008). ...
South Asia has a remarkable diversity of squir-
rels and they play an important role in the ecosystem func-
tioning of this region. An evaluation on a global scale
showed that the tropics of South and Southeast Asia, whilst
being the centre of high diversity are areas that have given
rise to very less scientific knowledge. Thus, this study aims
to understand the temporal and spatial variation in squirrel
research in South Asia and to map the thematic research
areas on squirrel research and understand, how much fund-
ing has the squirrel research attracted in the past few dec-
ades. Keeping the research goals in mind, a systematized
search for papers following the “Preferred Reporting Items
for Systematic Reviews and Meta-Analyses” (PRISMA)
framework was followed. The articles were searched in Sco-
pus. It was found that the greatest number of studies were
published between 2011–2020 showing a positive trend on
a temporal scale. A total of 43 studies have been done which
comprises to 76 percent of the total studies conducted are
in India and India shares a huge percentage of major Sciu-
ridae species research in South Asia. Also, majority of the
research is conducted on three species of giant squirrels in
South Asia
... GLAPAS is known to be a structurally rich, mature spruce and mixed forest specialist species during the breeding season [122,[124][125][126][127][128][129][130][131], and clearcuts and logging have been shown to affect habitat suitability [131], as well as population size [132]. Structurally rich mature forests are habitats with some of the highest densities of small mammals [79][80][81][82][83][84][85]133]. Latvia and Finland are the countries in Europe with the highest forestry activity, even in protected areas [134]. ...
Strong numerical and functional responses of owls to voles in cyclic environments are well known. However, there is insufficient knowledge from the boreonemoral region in particular, with depleted populations of small mammals. In this study, we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings, and population trends to lay out the numerical response of six owl species to dampened small mammal population cycles. We found temporarily increasing food niche breadth in tawny and Ural owls. There were no other responses in the tawny owl, whereas the breeding performance of three forest specialist species—pygmy, Tengmalm’s, and Ural owls—corresponded to the vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls decreased, and the change in the Ural owl population can be attributed to the depletion of small mammal populations. We found evidence of a carry-over effect in the eagle owl arising from a strong correlation of declining breeding performance with the small mammal abundance indices in the previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate of the likely effects of habitat destruction that needs to be investigated further, with stronger responses in more specialized (to prey or habitat) species.
... Species richness is a fundamental measurement of biodiversity used in ecological models and conservation plans (Gotelli and Colwell, 2001;Guillera-Arroita et al., 2019), allowing for quantitative analysis of biodiversity both within (i.e., alpha diversity) and between (i.e., beta diversity) communities. Environmental characteristics of an area is one of the most influential factors affecting such patterns at all scales (Pulliam, 1988;Carey and Johnson, 1995;Urquiza-Haas et al., 2009). By providing numerical values (Wilson et al., 2012), species richness allows researchers to infer how biotic and abiotic variables influence alpha and beta diversity through comparison of differing sites and regions. ...
Species richness within a site (i.e., alpha diversity) and between sites (i.e., beta diversity) are important measurements of biodiversity utilized in wildlife research and management. However, novel occupancy modeling approaches, especially at large spatial scales and in conjunction with other analyses of biodiversity, remain scarce in studies of mammalian biodiversity across forested landscapes. We assessed alpha and beta diversity of mammals across a 16,058-km² region of southern Illinois, USA, between January and April of the years 2008 to 2010. We deployed camera traps, measured habitat variables, applied hierarchical occupancy modeling and meta-analysis techniques to investigate alpha diversity, and used partial redundancy analyses and partial Mantel tests to investigate beta diversity. We collected 86,486 photographic captures of mammals. Alpha diversity values ranged from 3-10; models incorporating Simpson’s diversity index of patch types, distance to major road, and agriculture clumpiness index were most supported. Forest proximity and percentage forest cover explained minor variation in beta diversity, and we found weak, positive correlations between beta diversity and percentage forest cover and forest proximity index. Mammalian biodiversity was strongly influenced by generalist species and highest with (1) moderate levels of habitat heterogeneity, (2) low to moderate levels of anthropogenic influence, and (3) nearby forest cover. Anthropogenic influences and the presence of agriculture appeared to increase species richness by providing novel food resources and additional habitat that generalist species could exploit while also being tolerant of any accompanying landscape fragmentation or disturbance. While dominated by generalist species, our local mammalian community had an affinity for forest cover, reinforcing the importance of forested habitat to these species in hardwood forest systems. Our study demonstrates the usefulness of hierarchical modeling approaches and the importance of examining biodiversity through varying measurements.
... GLAPAS is known to be a structurally rich mature spruce and mixed forest specialist species during the breeding season [124,[126][127][128][129][130][131][132][133], and clearcuts and logging are shown to affect habitat suitability [133] as well as population size [134]. Structurally rich mature forests are habitats with some of the highest densities of the small mammals [79][80][81][82][83][84][85]135]. Both Latvia and Finland are countries in Europe with the highest forestry activity even in protected areas [136]. ...
Strong numerical and functional response of owls to voles in cyclic environments is well known, but there is insufficient knowledge from boreonemoral region, in particular, with depleted populations of the small mammals. In this study we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings and population trends to describe the numerical response of six owl species to dampened small mammal population cycles. We found temporarily in-creasing food niche breadth in tawny and Ural owls. There were no other responses in tawny owl, whereas the breeding performance of three forest specialist species – pygmy, Tengmalm`s and Ural owls – were similar to vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls are decreasing and the change in Ural owl can be attributed to the depletion of small mammal populations. We found evidence of carry-over effect in eagle owl arising from strong correlation of declining breeding performance with the small mammal abundance indices in previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate to overwhelming impacts of habitat destruction with stronger response in more specialized (to prey or habitat) species.
... Among the study sites, Berembun FR I harbor the highest number of small vertebrates with 50 species, followed by Angsi FR and Berembun FR II with 43 and 39 species, respectively (Table 1-3). Based on the observation, the remains of good forest covers (low canopy openness) at Berembun FR I may correlate to a high diversity of small vertebrates as it could offer better habitat structural complexity with favorable microhabitats and microclimatic conditions to support different species requirements [18,19,20]. In addition, Berembun FR I fronting less human intrusion may be due to rugged terrains compared to Angsi FR and Berembun FR II. ...
Surveys of small terrestrial vertebrates were conducted at identified Central Forest Spine (CFS) ecological corridor named CFSII SL7 (Secondary Linkage-7) involving Angsi Forest Reserve and Berembun Forest Reserve in Negeri Sembilan. The surveys were conducted in February, April, and September 2018. The main objective of these surveys is to update the checklist of small vertebrate species recorded in the corridor. Three plots were established, two located in Berembun FR, referred to as Berembun FR I and Berembun FR II, while one located at Angsi FR. A total of 100 collapsible cage traps, three harp traps, 10 mist nets, and 25 pitfall traps were deployed at each site. These traps were set for five consecutive nights per session, with two sampling sessions per site. In addition, direct observations and active searches were also conducted for arboreal species and herpetofauna respectively. A total of 326 individuals comprising 26 species of small mammals (eight families), 43 species of avifauna (19 families), and 22 species of herpetofauna (10 families) were recorded during the surveys. Berembun FR I harbor the highest number of small vertebrates (50 species), followed by Angsi FR and Berembun FR II with 43 and 39 species, respectively. In addition, 39 of the overall documented species are additionally recorded as small vertebrates compared to a compilation of previously listed species at both forest reserves. Through these results, it is hoped that the significance of these fragmented forests under CFSII SL7 as crucial habitats for small vertebrates can be further highlighted, and appropriate conservation measures must be taken to safeguard the small vertebrate population in these areas.
Natural disturbances such as fire, insect pests, and windstorms are affecting forests with increasing intensity. Fallen and damaged trees are commonly removed by salvage logging, which can affect tree regeneration and browsing pressure. Yet, the interaction of logging intensity and browsing and their cumulative effects on natural tree regeneration remain poorly understood. We applied three treatments of differing logging intensity to temperate beech (Fagus sylvatica) forest affected by windstorm, using adjacent undamaged forest as reference. We monitored tree regeneration for the first four years following disturbance, and browsing on experimentally planted one-year-old Quercus robur saplings for one year on a total of 20 plots. Natural tree regeneration was present on all plots, regardless of treatment. Species richness and cover of natural regeneration did not differ between disturbance treatments, tree species composition shifted towards early successional species with increasing management intensity, i.e., decreasing amount of deadwood remaining on-site. Community composition of regenerating trees on plots with intensive logging was significantly dissimilar to undamaged forest. Browsing intensity by roe deer decreased with decreasing logging intensity. Browsing by voles and mice showed the opposite effect direction. We show that salvage logging intensity influences species composition of natural regeneration, and that dead wood retention modulates browsing. Salvage logging of moderate intensity promotes the regeneration of early-and late-successional tree species similarly, thereby reducing the need for afforestation.
The presence and abundance of organisms within an ecosystem often correlate with habitat variables that may have few, or unknown, functional values. Understanding the functional role of these variables is especially important for organisms occupying landscapes managed for timber production and containing diverse habitat patches of different quantities and structures of vegetation. We investigated the strength of associations reported in the literature between small mammal generalists and vegetation. On an industrially logged landscape in northern California, we used occupancy and mark-recapture analyses across three years to estimate presence and total numbers for woodrats (Neotoma fuscipes (Baird 1858)) and deer mice (Peromyscus maniculatus (Wagner 1845)) related to vegetative attributes on coniferous and non-coniferous sites. Abundances of the small mammals correlated positively with shrub cover and hardwoods for woodrats and with shrubs and masting species for deer mice. Indices describing the value of vegetation features for both food and cover, but not these resources independently, described both species’ presence and abundances best. We demonstrated that shrubs and non coniferous trees are particularly important for small mammals and should be of particular focus to forest managers in the Sierras and mountains with similar forest structures.
We operated pitfall arrays with 5-m drift fences at 30 stands in western Oregon and Washington for 180 days. Pitfall arrays had a pronounced removal effect on small mammals (but not on the herpetofauna) during the 1st 60 days of trapping. Conventional short (10-day) trapping periods were only adequate to detect the most common mammals. About 60 days were needed to compile a relatively complete species list (>85% of species captured) at each site. Reptiles were caught almost exclusively in the summer; amphibian captures were correlated with increased precipitation in the fall. Short (2.5-m) drift fences were less effective than the standard length of 5 m. Funnel traps captured few forest vertebrates. Pitfalls captured more insectivorous mammals than did snap traps, but snap traps were more effective for a few cricetid rodents. Pitfall arrays are adaptable to many habitats and can help assess the presence of small vertebrates, such as shrews and amphibians, that are undersampled by other techniques.
Virgin forest in the Douglas-fir ( Pseudotsuga taxifolia ) region of northwestern California is a sterile habitat for wildlife. Dense shade and competition from large old trees prevent the growth of nearly all bushy and herbaceous vegetation except a weak understory of tan oak ( Lithocarpus densiflora ). Food for animals is scarce.
The immediate effect of logging is to flood the ground with light. Then tan oak begins a rapid, aggressive growth, and many kinds of herbs, of which fireweed ( Erechtites ) is one of the most abundant, become established. In terms of plant succession, the cutover changes from bare ground to weeds to brush and finally to a climax of Douglas-fir or more often, tan oak. During the middle stages, food for animals is plentiful.
Small seed-eating mammals are one of the factors that result in the economically undesirable climax of oaks instead of conifers. Mice in particular, because of their fondness for coniferous seeds, are responsible in part at least for the failure of natural seeding to restock many cutovers with firs; and they make artificial seeding difficult and often impossible.
In the Douglas-fir region of California, large tracts of old timber are slated to be logged within the next few years. The usual method is to clear-cut blocks that are fifteen to twenty acres in size and burn the resulting slash. Before silvicul-turists can prepare a successful plan for reforesting these cutovers, information is needed about the various factors that hinder coniferous reproduction. As a contribution toward that end, this paper gives the results of a trapping survey of small mammals at elevations between 2,000 and 4,000 feet in Humboldt and Trinity counties near Salyer. The purpose of the survey, which was undertaken in cooperation with the California Forest and Range Experiment Station of the United States Forest Service, was to …
Mark-recapture was conducted from 1981 through 1983 in the Cascade Range of Oregon to examine the use of riparian and upland habitats by small mammals. Both number of individuals and species richness were greater in riparian than in upland areas. Because of the occurrence of several less-commonly captured species in riparian locations, species evenness was greatest in the upland. Among Insectivora, Sorex monticolus and S. trowbridgii were captured most often on riparian sites. Among insectivores adult males weighed more in riparian zones. Three rodents (Peromyscus maniculatus, Microtus oregoni, and Zapus trinotatus) were captured more frequently in riparian habitats; two rodents (Tamias townsendii and Clethrionomys californicus) were captured more frequently in upland habitats. Among all rodents, except Z. trinotatus, adult males weighed more in riparian areas. Mustela erminea was captured more frequently in riparian sites. Eight species had greater numbers of adults in breeding condition in riparian than in upland habitats. Conversely, six species had greater numbers of juveniles in the upland. Data from several species, including T. townsendii, P. maniculatus, Z. trinotatus, and Glaucomys sabrinus, indicated that riparian habitats act as a species source and upland areas act as a dispersal sink.
Plant composition and coverage and small mammal populations were compared in virgin forest (control) and clearcut (experimental) areas from April 1954 to October 1965. Changes in ground cover vegetation were modest on the control area but marked on the experimental area. A late fall burn on the experimental area may have retarded herbaceous plant establishment. Nearly half of the herbaceous species were invaders not found in the virgin Douglas-fir (Pseudotsuga menziesii) forest. Ground plant coverage was less than 23% in the virgin forest; 1 year after the clearcut area was burned, the cover was 2%; and by 10 years it was above 53%. Woody plant coverage (mostly sprouts) was slightly more abundant the first 2 years after burning. Herbaceous species then became dominant for a 3-year period, after which woody plants gradually gained dominance. Deer mice (Peromyscus maniculatus) increased on the experimental area soon after the burn. The populations varied from an estimated 0.9 to 12.8 animals per acre and fluctuated widely and irregularly. Townsend's chipmunk (Eutamias townsendii), Oregon vole (Microtus oregoni), and snowshoe hare (Lepus americanus) populations also increased on the area at different periods after the burn. Trownbridge's shrews (Sorex trowbridgii), vagrant shrews (Sorex vagrans), and ermine (Mustela erminea) were present on both areas in relatively low numbers. Redback voles (Clethrionomys occidentalis), Douglas' squirrels (Tamiasciurus douglasii), and northern flying squirrels (Glaucomys sabrinus) were not found on the clearcut. California ground squirrels (Spermophilus beecheyi) migrated to the clearcut and established a modest population. Richardson's voles (Microtus richardsoni), jumping mice (Zapus trinotatus), bushy-tailed woodrats (Neotoma cinerea), and a pika (Ochotona princeps) were visitors.
(1) If chipmunk (Eutamias townsendii Bachman) populations are limited by food when independent of other factors, then provision of a preferred supplemental food should increase density and related demographic attributes. (2) Chipmunk populations were live-trapped from the autumn of 1976 to the spring of 1980 in two coastal forest-cutover ecotones at Maple Ridge, British Columbia. Extra food was supplied during 1977 and 1978. (3) The fed population increased 40-50% above the control population and maintained this difference through the 2 years of the experiment. (4) Juvenile survival, during the summer and through the winter hibernation period, was increased in the fed population over that of the control. (5) Body weights were higher and juveniles grew significantly faster in the population with extra food than in the control. Range length tended to be less for chipmunks in the fed population. (6) After the food was withdrawn, the population density declined on the experimental area and related demographic variables became similar with those in the control. (7) We conclude that food limits population size in Townsend's chipmunk.
Voles of the species Microtus oregoni oregoni, M. townsendii townsendii, and M. montanus canicaudus were collected from Coast Range and Williamette Valley habitats in webstern Benton County, Oregon, from June 1957 to January 1959, in an effort to determine habitat preferences. Collecting results indicate that the Oregon vole is a species of the Coast Range mountains. It is found in all Coast Range (Douglas fir) habitats, but prefers grassy cutover areas. Townsend voles are most closely associated with both Coast Range and Valley riparian situations especially where dense stands of sedge and grass occur. The gray-tailed vole is found on all agricultural lands, especially in fields and pastures of grass and legumes and along fence rows. This species is not associated with Coast Range habitats. The gray-tailed vole is at all times a potential agricultural pest.
Some statistical "distributions" which, when plotted on an "arithmetical" basis, do not in the least resemble a normal or Gaussian distribution, become very similar to one when plotted on a logarithmic or "geometrical" basis. In this paper I examine in particular the difference of two declining exponential curves, and, as a special case, a simple single declining exponential. On a logarithmic base these curves are somewhat skewed, but none the less are very close to a lognormal, and nearly all the variance can be accounted for (something like 99%), but there seems to be a limited range of "standard deviations" that can be accommodated. In human ecology, for instance, women's age at first marriage, which among western nations is known to be close to a lognormal, can be slightly better fitted by the difference of two declining exponentials, and a physical interpretation can be given to the latter, though not so easily to the former. The same thing is true of the failure of industrial products under repeated impact, or under prolonged stress. The apparently lognormal distribution of commonness and rarity differs from these in having a much greater value of the standard deviation, and it is not so easily explained. This may be because it is, in fact, a totally different phenomenon, but there is also a possibility that some modification or extension of the present paper may point the way to an explanation.