Predicting Pasture and Forest Landowner Intention to Create Early Successional Habitat

As human land uses expand across the landscape, the management practices of private landowners are an essential part of effective conservation. Early successional habitats (ESH) and the species that depend on them are a priority in the eastern United States, and efforts to create ESH on private lands has primarily focused on forest landowners and timber harvests. Private pasture lands in a forested landscape present an additional opportunity to create and maintain ESH, yet our understanding of landowner values and attitudes about management strategies in pastures is lacking. To address this, we surveyed private landowners in 5 Virginia counties who own ≥10.1 ha at >610 m elevation (n = 503). Our primary objective was to understand how a variety of factors such as landowner values, past experience with habitat management, and perceived barriers to carrying out habitat management are associated with private landowner intention to carry out 7 ESH management strategies (i.e., reduced mowing, reduced grazing, timber harvests within forest, timber harvests at a field-forest border, prescribed fire, use of machinery, and use of herbicides to control invasive species) for the benefit of wildlife in the next 5 years. We used boosted regression trees to determine which factors best predicted the intention to carry out each management strategy. We were able to predict accuracy >75% of the time for landowner intention to engage in open pasture and timber management strategies. Landowner values were not consistent across the different management strategies; landowners likely to reduce mowing or grazing valued ecological aspects of their land (e.g., pollinator habitat, water quality), whereas landowners likely to harvest timber valued hunting and revenue. Past experience with wildlife management was the strongest predictor of likelihood to reduce mowing and grazing. Our results suggest that expanding outreach efforts to include pasture management options would engage a broader set of landowners in creating ESH, especially if such efforts highlighted the benefits to pollinator species, water quality, and enhanced opportunities for hunting and other types of recreation. © 2021 The Wildlife Society.     

A Large-scale, Multihabitat Inventory of the Phylum Tardigrada in the Great Smoky Mountains National Park, USA: A Preliminary Report

An All Taxa Biodiversity Inventory (ATBI) is underway in the Great Smoky Mountains National Park (GSMNP), with the goal of attempting to identify all species of life in the 2000 km² park. The GSMNP is a hotbed of biodiversity, a U.N. Biosphere Reserve, and one of the largest protected, deciduous forests in the temperate world. We have completed two field seasons of work on the tardigrades in the park (2001–2002). As of July 2003, we have collected 420 samples from soil/decomposed leaf litter, lichens and mosses on trees, and stream sediment and periphyton. A few samples from caves, bird nests, and lichens/mosses on rocks were also collected. Samples were taken from within permanent plots established for the ATBI, representing the major biological communities of the GSMNP. Tardigrades were extracted from samples using centrifugation with Ludox AM™, individually mounted on microscope slides in Hoyer’s medium, and studied with phase contrast and DIC microscopy. We have examined 1524 slides from 60 samples as of July 2003. Prior to our work, only three species of tardigrades had been previously reported from a few samples in the park. We have now recorded 42 species, 8 of which we believe may be new to science. Species richness estimates were calculated using EstimateS 6 software for each of the major tardigrade habitats. Overall, we predict that there are 47 to 76 species in the GSMNP, with generally similar species richness in soil, lichen, moss, and stream habitats. Species richness estimates were also used to determine that the number of tardigrade species was greater in mosses at breast height on trees than in mosses at the base of trees.     

Testing Pleistocene refugia theory: phylogeographical analysis of Desmognathus wrighti,a high-elevation salamander in the southern Appalachians

During the colder climates of the Pleistocene, the ranges of high-elevation species in unglaciated areas may have expanded, leading to increased gene flow among previously isolated populations. The phylogeography of the pygmy salamander, Desmognathus wrighti, an endemic species restricted to the highest mountain peaks of the southern Appalachians, was examined to test the hypothesis that the range of D. wrighti expanded along with other codistributed taxa during the Pleistocene. Analyses of genetic variation at 14 allozymic loci and of the 12S rRNA gene in the mtDNA genome was conducted on individuals sampled from 14 population isolates throughout the range of D. wrighti. In contrast to the genetic patterns of many other high-elevation animals and plants, genetic distances derived from both molecular markers showed significant isolation by distance and genetic structuring of populations, suggesting long-term isolation of populations. Phylogeographical analyses revealed four genetically distinct population clusters that probably remained fragmented during the Pleistocene, although there was also evidence supporting recent gene flow among some population groups. Support for isolation by distance is rare among high-elevation species in unglaciated areas of North and Middle America, although not uncommon among Plethodontid Salamanders, and this pattern suggests that populations of D. wrighti did not expand entirely into suitable habitat during the Pleistocene. We propose that intrinsic barriers to dispersal, such as species interactions with other southern Appalachian plethodontid salamanders, persisted during the Pleistocene to maintain the fragmented distribution of D. wrighti and allow for significant genetic divergence of populations by restricting gene flow.     

Niche expansion after competitor extinction? A comparative assessment of habitat generalists and specialists in the tree floras of south‐eastern North America and south‐eastern Europe

Aim The aim of this study was to test R.H. MacArthur’s hypothesis that realized niche breadth is constrained by species pool size – the greater the number of species in a region, the more competition restricts the distribution of each species with respect to environmental tolerances and habitat characteristics. Location The northern Balkan region in south‐eastern Europe (Illyrian Floristic Province) and the southern Appalachian region of the USA. Methods We compared co‐occurrence‐based distributions of habitat specialization of tree species in two geographic regions that are ecologically similar but differ in species pool size. We applied two methods. First, we used a rank‐ordering of species along a gradient of estimated niche breadth that is based solely on species co‐occurrence information derived from vegetation databases from each region. To compare niche‐breadth distributions of different datasets we developed a procedure that standardizes expected values of species co‐occurrences independently of the size of the species pool. Second, we calculated species turnover along an elevational gradient for both regions, estimated as the rate of decay of compositional similarity with elevation distance. Results Despite a twofold larger species pool, and in contrast to our hypothesis, there was no greater specialization trend in the tree species of the southern Appalachian region, regardless of phylogenetic subgroupings or whether rare species were included. After correcting for differences in species pools, the similarity decay with elevation distance was marginally stronger in the southern Appalachian region. Main conclusions MacArthur’s hypothesis was not supported by our analysis. While the compositional distance decay with elevation revealed only a slight trend towards narrower realized niches in the tree flora of the southern Appalachian region, the co‐occurrence approach suggested the opposite. Our results indicate that species distributions are largely constrained by environmental tolerances, and that biotic pressure in the form of competition from ecologically similar species plays a relatively minor role in the ability of species to establish mature individuals in different habitat types.     

Temperate mountain grasslands: a climate‐herbivore hypothesis for origins and persistence

Temperate montane grasslands and their unique biotas are declining worldwide as they are increasingly being invaded by forests. The origin and persistence of these landscapes have been the focus of such controversy that in many areas their conservation is in doubt. In the USA some biologists have largely dismissed the grass balds of the Southern Appalachians as human artifacts or anomalous and transitory elements of regional geography, worthy of only limited preservation efforts. On the basis of information from biogeography, community ecology, regional history and palaeontology and from consideration of two other montane grassland ecosystems—East Carpathian poloninas and Oregon Coast Range grass balds—we hypothesize that these landscapes are more widespread than was formerly recognized; they are, in many cases, natural and ancient and largely owe their origin and persistence to past climatic extremes and the activities of large mammalian herbivores.     

Demographics of an Experimentally Released Population of Elk in Great Smoky Mountains National Park

ABSTRACT We assessed the potential for reestablishing elk (Cervus elaphus) in Great Smoky Mountains National Park (GSMNP), USA, by estimating vital rates of experimentally released animals from 2001 to 2006. Annual survival rates for calves ranged from 0.333 to 1.0 and averaged 0.592. Annual survival for subadult and adult elk (i.e., ≥ 1 yr of age) ranged from 0.690 to 0.933, depending on age and sex. We used those and other vital rates to model projected population growth and viability using a stochastic individual-based model. The annual growth rate (λ) of the modeled population over a 25-year period averaged 0.996 and declined from 1.059 the first year to 0.990 at year 25. The modeled population failed to attain a positive 25-year mean growth rate in 46.0% of the projections. Poor calf recruitment was an important determinant of low population growth. Predation by black bears (Ursus americanus) was the dominant calf mortality factor. Most of the variance of growth projections was due to demographic variation resulting from the small population size (n = 61). Management actions such as predator control may help increase calf recruitment, but our projections suggest that the GSMNP elk population may be at risk for some time because of high demographic variation.     

Challenges of DNA-Based Mark-Recapture Studies of American Black Bears

Abstract: We explored whether genetic sampling would be feasible to provide a region-wide population estimate for American black bears (Ursus americanus) in the southern Appalachians, USA. Specifically, we determined whether adequate capture probabilities (p > 0.20) and population estimates with a low coefficient of variation (CV < 20%) could be achieved given typical agency budget and personnel constraints. We extracted DNA from hair collected from baited barbed-wire enclosures sampled over a 10-week period on 2 study areas: a high-density black bear population in a portion of Great Smoky Mountains National Park and a lower density population on National Forest lands in North Carolina, South Carolina, and Georgia. We identified individual bears by their unique genotypes obtained from 9 microsatellite loci. We sampled 129 and 60 different bears in the National Park and National Forest study areas, respectively, and applied closed mark-recapture models to estimate population abundance. Capture probabilities and precision of the population estimates were acceptable only for sampling scenarios for which we pooled weekly sampling periods. We detected capture heterogeneity biases, probably because of inadequate spatial coverage by the hair-trapping grid. The logistical challenges of establishing and checking a sufficiently high density of hair traps make DNA-based estimates of black bears impractical for the southern Appalachian region. Alternatives are to estimate population size for smaller areas, estimate population growth rates or survival using mark-recapture methods, or use independent marking and recapturing techniques to reduce capture heterogeneity.