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Libertyville, IL, United States

Fahey R.T.,Morton Arboretum | Maurer D.A.,Lake County Forest Preserve District | Bowles M.L.,Morton Arboretum | McBride J.,Morton Arboretum
Natural Areas Journal | Year: 2014

The forests and woodlands of the Prairie Peninsula region in the Midwestern USA have been heavily impacted by human influences over the past ∼150 years. Current composition, structure, and dynamics in forest communities across the region lie outside the historical range of variability. However, areas along major waterways were afforded greater fire protection historically than the landscape as a whole (and are common locations for modern natural areas), and historical and modern conditions may be more analogous in these locations. This study assessed composition and structure of woodlands in a series of natural areas along the Des Plaines River in Lake County, Illinois, and related current conditions to historical baselines for the locality and region. Modern composition and structure in even these fire-protected habitats appear to lie outside the historical range of variability. High canopy cover, stem density, and dominance by sugar maple (Acer saccharum Marsh.) and European buckthorn (Rhamnus cathartica L.) are especially inconsistent with historical conditions. Current structure suggests a continued trajectory toward homogenized, closed-canopy ecosystems with increased dominance by mesophytic and invasive species and decreased importance of historically-dominant oak (Quercus spp.) species. Community-specific management strategies focused on modifying canopy structure and composition will be necessary to shift these communities toward conditions of increased light availability, structural complexity, and biological diversity. Strategies to achieve these goals are currently not well established, especially those that could be applied in urban natural areas. Implementation of multiple approaches in an adaptive management framework would aid in developing best management practices for wooded ecosystems in the region. Source

Sacerdote-Velat A.B.,Lincoln Park Zoo | Earnhardt J.M.,Lincoln Park Zoo | Mulkerin D.,Lincoln Park Zoo | Boehm D.,Lincoln Park Zoo | Glowacki G.,Lake County Forest Preserve District
Animal Conservation | Year: 2014

Headstarting is a conservation technique for improving survival of species with high juvenile mortality by accelerating growth rate and increasing body size of captive-born young. With reptiles, headstarts are often kept active year-round to achieve body size goals and increase survival, omitting overwintering (brumation). As brumation is part of the life cycle of reptiles, there may be tradeoffs related to temperature response post-release when reptiles are kept active. Upon release into habitats, reptiles are either soft released, where acclimation is provided with in situ enclosures, or hard released without acclimation, directly into habitat. Soft releases have resulted in greater survival and site fidelity than hard releases, but evaluations with snakes are rare. We used a comparative approach to examine effects of brumation versus year-round activity on prerelease growth and survival of smooth green snake Opheodrys vernalis headstarts. We estimated short-term post-release daily survival rates of headstarts and compared movements of hard and soft released snakes. Despite decreases in body mass during brumation, prerelease body size, growth rate and survival did not differ among brumation treatments. Brumated headstarts exhibited rapid compensatory growth, attaining the size of active headstarts within 2 months of brumation. We observed qualitative evidence of reproductive potential in brumated snakes with the production of spermatozoa and unfertilized eggs, which was absent in active headstarts. The short-term survival rate of all headstarts during post-release tracking was 0.83 (±0.01), but we lacked power to examine differences in survival among release treatments. Daily movements did not differ among release treatments. Soft releases had slightly greater recaptures, facilitating monitoring. Although brumation comparisons produced equivalent prerelease growth and survival, as a precautionary measure for post-release survival, we recommend incorporating brumation into headstarting efforts. While further study with other reptiles is warranted, we recommend a comparative framework in planning headstarting efforts with additional species. © 2014 The Zoological Society of London. Source

Urbanek R.E.,Southern Illinois University Carbondale | Nielsen C.K.,Southern Illinois University Carbondale | Glowacki G.A.,Lake County Forest Preserve District | Preuss T.S.,Lake County Forest Preserve District
American Midland Naturalist | Year: 2012

Despite the widespread interest in plant community restoration, few studies have assessed white-tailed deer (Odocoileus virginianus Zimm.) herbivory on herbaceous species and even fewer studies have focused on deer herbivory in restored plant communities. During 20072009, we investigated the effect of deer density and associated deer browse on two restored forest and three restored savanna plant communities in Lake County, Illinois. We used 300 small (1.4 m diameter × 1.6 m height) exclosed plots and 1-m 2 unexclosed plots to compare the effects of deer herbivory on forbs. We quantified and compared percent non-herbaceous ground cover, species diversity, species evenness, and floristic quality between exclosed plots and unexclosed plots, as well as among preserves within each plant community type. Species diversity and floristic quality of forbs may be maximized at a deer density between 622 deer km 2 in restored forest communities in northeastern Illinois. Floristic quality was higher in exclosed plots compared to unexclosed plots at all savanna sites. In both plant communities, species evenness may have increased with higher deer density due to an increase in non-preferred plants and non-native species invading locations where preferred native forbs were chronically consumed. Our results highlight the importance of assessing the species diversity, evenness, and floristic quality of target plant communities to determine the impact of deer herbivory at varying deer densities. © 2012, American Midland Naturalist. Source

Urbanek R.E.,Southern Illinois University Carbondale | Nielsen C.K.,Southern Illinois University Carbondale | Preuss T.S.,Lake County Forest Preserve District | Glowacki G.A.,Lake County Forest Preserve District
Wildlife Society Bulletin | Year: 2012

Wildlife biologists require density estimates for white-tailed deer (Odocoileus virginianus) to facilitate management. Aerial surveys are often used to obtain density estimates, but are subject to problems necessitating the consideration of novel techniques. During winters 2008 and 2009, we estimated deer density on 6 forest preserves near Chicago, Illinois, USA, using aerial surveys and pellet-based distance sampling (PBDS) methods to provide a comparison of these 2 density-estimation techniques. Density estimates from aerial surveys were obtained by dividing both the raw count of deer observed on each preserve (unadjusted aerial density) and the raw count divided by 0.75 (i.e., assuming a 75% detection rate; adjusted aerial density) by the area of the preserve. We calculated deer densities from PBDS methods using Program DISTANCE 5.0 (PBDS density) and used paired t-tests to compare density estimates between PBDS and aerial survey techniques. Unadjusted aerial density (10-29 deer/km2) and adjusted aerial density (13-39 deer/km2) estimates did not differ (t11 = 1.99-0.44, P = 0.071-0.666) from PBDS density estimates (12-36 deer/km2). We also compared costs and found PBDS (US$85/survey) was 88% cheaper than aerial surveys (US$722/survey). Problems with bias and precision exist with both methods, and managers should give them serious consideration when choosing which method to use to estimate deer densities. Given accurate pellet decay and deposition rates and a large sample size of pellet groups, PBDS may be advantageous due to less bias in density estimates, no dependence on continuous snow cover, cheaper survey costs, and no need for elaborate equipment or for professional biologists to conduct surveys. However, future research needs to address how to reduce coefficient of variations and confidence intervals for PBDS so that differences among years can be better differentiated. © 2012 The Wildlife Society. Source

Urbanek R.E.,Southern Illinois University Carbondale | Nielsen C.K.,Southern Illinois University Carbondale | Glowacki G.A.,Lake County Forest Preserve District | Preuss T.S.,Lake County Forest Preserve District
Natural Areas Journal | Year: 2012

Most studies of white-tailed deer (Odocoileus virginianus Zimm.) herbivory focus on a few forb species or single sites in forest plant communities. However, managers require assessments of herbivory impacts across varying deer densities and in multiple plant communities, including wetlands and savannas where there is limited knowledge about the impacts of deer on herbaceous vegetation. During 2008 and 2009, we investigated deer herbivory impacts at six forest preserves near Chicago, Illinois. We sampled 192 browse transects in two forest, two savanna, and two wetland sites; sites were paired within each plant community type based on deer density (i.e., high vs. low). We used plant community metrics (i.e., percent non-vegetated ground cover, species diversity and evenness, and floristic quality) to quantify and compare herbivory impacts on vegetation between preserves. We observed higher grass cover (0.001 < P < 0.012), lower species diversity (0.001 < P < 0.041), and lower floristic quality (0.001 < P < 0.030) in preserves containing higher deer densities (2229 deer/km 2; low-density populations were 619 deer/km 2) for all three plant community types. Managers should be aware that deer are negatively affecting forest, savanna, and wetland plant communities at densities of > 20 deer/km2 in the Great Lakes region. We further suggest managers use plant community metrics, rather than single indicator species, to monitor deer herbivory. Source

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