Showing papers in "American Midland Naturalist in 2003"
TL;DR: The timing of mortalities, and other factors, suggest that most mortality involves migrant rather than resident breeding bats, which is in line with previous studies of wind power development on wildlife.
Abstract: In 1994 a major wind power development project was initiated in southwest Minnesota that may eventually produce 425 megawatts (MW) of electricity. The wind plant currently consists of 3 phases that total 354 turbines capable of generating 236 MW. During a study conducted from 1996–1999 to assess effects of wind power development on wildlife, 184 bat collision fatalities were documented within the wind plant. Hoary bats (Lasiurus cinereus) and eastern red bats (L. borealis) comprised most of the fatalities. After correcting bat fatality estimates for searcher efficiency and scavenger removal rates, we estimated that the number of bat fatalities per turbine ranged from 0.07 per y at the Phase 1 wind plant to 2.04 per y at the Phase 3 wind plant. The timing of mortalities, and other factors, suggest that most mortality involves migrant rather than resident breeding bats.
139 citations
TL;DR: Partial timber harvests that leave a relatively closed canopy appear to promote or improve northern myotis foraging habitat in heavily forested landscapes, however, the long-term ecological impacts on bats and other biota from this silviculturally unacceptable practice are unclear.
Abstract: We examined home range size and habitat use of nine female northern myotis (Myotis septentrionalis) within an intensively managed forest in the central Appalachians of West Virginia. Using the 95% adaptive kernel method, we calculated a mean home range of 65 ha. Northern myotis used recent diameter-limit harvests and road corridors more than expected based on availability of these habitats. Intact forest stands and more open deferment harvested stands were used less than expected based on the availability of these habitats, although intact forest stands still constituted the overall majority of habitat used. Partial timber harvests that leave a relatively closed canopy appear to promote or improve northern myotis foraging habitat in heavily forested landscapes. However, the long-term ecological impacts on bats and other biota from this silviculturally unacceptable practice are unclear.
95 citations
TL;DR: This study demonstrates how the brome functional type alters several properties in an ecosystem traditionally dominated by perennial grasses.
Abstract: Annual brome grasses, Bromus japonicus and B. tectorum, are common exotic plants in the northern mixed grass prairies of North America. As annuals, the bromes die following seed set in late spring, creating a functional difference between them and native perennial grasses because perennials continue to maintain live shoots into the summer and root systems throughout the year. Our objective was to investigate how this functional difference alters ecosystem properties over the growing season, including soil moisture content, quantity of plant biomass, litter accumulation and aboveground litter decomposition. We conducted an experiment in which the annual bromes were removed from treatment plots to compare with adjacent reference plots. While this experiment served as a direct test for brome impacts, observational plots also were sampled to determine if impacts were apparent in an unmanipulated system. A litter bag experiment was conducted to evaluate impacts of brome grasses on decomposition. Experimental removal of brome grasses led to more biomass both above- and belowground at the end of the growing season, and high brome observational plots averaged 28% less aboveground biomass and 40% less belowground biomass than low brome plots. In contrast, removal of brome grasses did not produce a consistent impact on soil moisture content between sites or among months, and none of measurable impacts from the removal experiment were significant in the observational study. Bromes slowed decomposition of aboveground litter at both sites. However, the overall impact on litter accumulation was only significant at one site, where brome removal reduced surface litter in the latter half of the growing season and high brome observational plots averaged 36% more litter than low brome plots. This study demonstrates how the brome functional type alters several properties in an ecosystem traditionally dominated by perennial grasses.
94 citations
TL;DR: Investigation of spatial point pattern analysis of trees in a silvicultural experiment found that increased disturbances could lead to more opportunities for A. altissima to invade, interact with R. pseudoacacia and other native species and potentially have an effect on the native plant community.
Abstract: Invasive exotic plants can persist and successfully spread within ecosystems and negatively affect the recruitment of native species. The exotic invasive Ailanthus altissima and the native Robinia pseudoacacia are frequently found in disturbed sites and exhibit similar growth and reproductive characteristics, yet each has distinct functional roles such as allelopathy and nitrogen fixation, respectively. Spatial point pattern analysis of trees in a silvicultural experiment was used to analyze the potential intraspecific and interspecific interference between these two species by looking at their individual spatial distribution and their spatial association. Analysis of spatial point patterns in the field with Ripley's K indicated that A. altissima and R. pseudoacacia were positively associated with each other along the highly disturbed skid trails in the majority of the field sites. Robinia pseudoacacia was clumped in the majority of the sites, whereas A. altissima was randomly distributed in most sites. Locally, increased disturbances could lead to more opportunities for A. altissima to invade, interact with R. pseudoacacia and other native species and potentially have an effect on the native plant community.
77 citations
TL;DR: Symbiotic germination was evaluated to determine need for cold moist stratification to enhance seed germination and seedling development and identify the mycobionts that support in vitro Germination and development and results indicate that in vitro development of P. praeclara is best supported when stratified seeds are cultured with fungi isolated from young seedlings.
Abstract: In vitro culture of mycotrophic leaf-bearing seedlings of federally threatened Platanthera praeclara Sheviak and Bowles, a terrestrial orchid native to the midwestern prairies, is reported for the first time. Symbiotic germination was evaluated to: (1) determine need for cold moist stratification to enhance seed germination and seedling development and (2) identify the mycobionts that support in vitro germination and development. Germination was improved by exposing seeds to both 4- and 6-mo stratification periods; whereas seeds without stratification failed to germinate in a pilot study. Pretreatment of seeds with 6 mo of stratification combined with inoculation with mycorrhizal fungus derived from a seedling (Ceratorhiza sp., UAMH 9847) supported development of higher stage protocorms and some leaf-bearing seedlings of P. praeclara. Protocorms with developing leaf primordia were also obtained by coinoculation with strains of Epulorhiza and Ceratorhiza. Fungi derived from mature P. praeclara pla...
73 citations
TL;DR: It is suggested that ≤8 y-old pine (Pinus spp.) habitats are important to bobcats, particularly females, as these habitats were selected by females at all spatial scales, however, the data also indicate that mature (>30 y) pine habitats are Important on the study area.
Abstract: Many factors influence bobcat (Lynx rufus) space use, movements and habitat selection, including prey distribution and density, season, breeding behaviors and intraspecific relationships. Knowledge of ranging behaviors and habitat selection is required to understand population dynamics and ecology of bobcats within temperate ecosystems. We radio-monitored 58 adult bobcats from 1989–1997 in central Mississippi. Males maintained larger home ranges and core areas than females, but sizes of these areas did not vary seasonally. Male bobcats moved at greater rates than females and bobcats moved at greatest rates during nocturnal periods. Movement rates were greatest during winter. Habitat selection at three spatial scales differed between genders and across seasons within gender. Our findings suggest that ≤8 y-old pine (Pinus spp.) habitats are important to bobcats, particularly females, as these habitats were selected by females at all spatial scales. However, our data also indicate that mature (>30 y...
65 citations
TL;DR: Although CRP is not equivalent to native prairie in terms of vegetation or arthropod diversity, CRP lands do support arthropid prey for grassland birds, and direct assays of the survivorship and fitness of birds on CRP compared to native shortgrass prairie are clearly warranted.
Abstract: The Conservation Reserve Program (CRP) was designed to reduce soil erosion and curb agricultural overproduction by converting highly erodible agricultural land to various forms of perennial habitat. It has had an incidental benefit of providing habitat for wildlife and has been beneficial in reversing population declines of several grassland bird species. However, the mechanisms behind these reversals remain unknown. One such mechanism may be differences in food availability on CRP vs. non-CRP land or between different types of CRP. The influence of CRP habitat type on the abundance of arthropod prey used by grassland birds has not been previously explored. We compared the abundance and diversity of arthropods among four CRP habitat types in Texas [replicated plots of exotic lovegrass (Eragrostis curvula), Old World bluestem (Bothriochloa ischaemum), mixed native grasses with buffalograss (Buchloe dactyloides) and mixed native grasses without buffalograss] and native shortgrass prairie. Attention...
63 citations
TL;DR: Overall, crayfish densities were significantly greater in intermittent streams than in permanent streams with density of O. punctimanus and O. ozarkae found in significantly greater densities than small individuals.
Abstract: Little is known regarding the impact of stream drying on community structure and habitat selection of lotic crayfish. Crayfish community structure was measured through quantitative sampling of riffle, run and pool habitats in 15 intermittent and 21 permanent streams in the Spring River watershed in the Ozark Plateau region of northern Arkansas and southern Missouri. MANOVA was used to determine whether stream permanence, habitat and crayfish size affect crayfish density and ANOVA was used to determine the effect of stream permanence and habitat type on species richness. Canonical Correspondence Analysis was used to determine the relationship between environmental variables and crayfish relative densities. Four crayfish species were collected: Orconectes marchandi, O. punctimanus, O. ozarkae and Cambarus hubbsi. Overall, crayfish densities were significantly greater in intermittent streams than in permanent streams with density of O. marchandi and O. punctimanus significantly greater in intermittent streams than in permanent streams. Densities of O. ozarkae and C. hubbsi did not differ significantly between the two stream types. Large individuals of O. punctimanus and O. ozarkae were found in significantly greater densities than small individuals. There was a significant relationship between crayfish relative density and abiotic environmental variables for permanent streams, but not for intermittent streams. In permanent streams, percent gravel, substrate diversity and mean current velocity were among the most important factors in determining crayfish density. Taxa mobility and predation risk are likely explanations for observed patterns of crayfish density.
63 citations
TL;DR: Both rhizomes and roots of goldenseal and ginseng are capable of regenerating plants, conferring a degree of short term resiliency following harvest, and this work has shown that harvested populations can recover if vegetative propagules remain in the soil.
Abstract: Goldenseal (Hydrastis canadensis L.) and American ginseng(Panax quinquefolius L.) have been harvested commercially for the past few centuries. Harvested populations can recover if vegetative propagules remain in the soil. Experiment I tested the efficacy of vegetative reproduction in goldenseal and ginseng. Partial and intact rhizomes and roots were planted in garden experiments in West Virginia and monitored for 1 y (goldenseal), and for 4 y (ginseng). During the experiment more than 40% of the propagule types of goldenseal (n = 5) and ginseng (n = 7) sprouted. Sprouting varied from year to year in ginseng, and dormancy and/or death occurred in both species. Of the ginseng propagules that sprouted, 77% were dormant for at least 1 y and half of those were not present in the final year of the experiment. Sprouting and reproductive status were dependent on propagule type for both species. In Experiment II we monitored recovery of wild populations of goldenseal and ginseng following natural and simu...
53 citations
TL;DR: Alliaria petiolata's pre-adaptation to achieve maximum rates of photosynthesis before the active growth of many native ground layer species when irradiance reaching the ground layer is high, and temperature and moisture conditions are favorable for the species, contributes to its successful spread and eventual domination of forest ground layers.
Abstract: Alliaria petiolata, an invasive biennial plant, actively grows and achieves high maximum rates of photosynthesis in early spring during its second growing season, when many indigenous ground layer species are still dormant and high levels of irradiance reach the forest floor. Alliaria petiolata also extends its growing season into the summer through stem elongation and production of new leaves that are adapted to ambient irradiance levels, unlike native deciduous forest spring ephemeral species or summer forbs. Photosynthetic rates for two populations of A. petiolata in a forest ground layer were measured in summer and fall of the plant's first growing season (1998) and in spring of the second growing season (1999). During the second growing season, estimates of native ground layer cover were made at 3–4 wk intervals from early April to late May. Maximum photosynthetic rates (AMax) were positively correlated (r2 = 0.791, df = 3, P = 0.0436) with mid-day irradiance reaching the forest ground layer...
53 citations
TL;DR: In this paper, the authors estimated the change in bird populations in the Eagle Lake Wetland Complex, Iowa with ongoing grassland and wetland restoration by linking geographic information system data and bird surveys in different land cover types (hayland, pasture, restored grassland, restored wetland and rowcrop agriculture) during the 1999-2001 breeding seasons.
Abstract: Native tallgrass prairie and wetland habitat in the Prairie Pothole Region of the United States have declined over the past two centuries. Bird communities using these habitats have also experienced widespread declines that are often attributed to severe habitat loss and fragmentation. We estimated the change, or turnover, in bird populations in the Eagle Lake Wetland Complex, Iowa, with ongoing grassland and wetland restoration by linking geographic information system data and bird surveys in different land cover types (hayland, pasture, restored grassland, restored wetland and rowcrop agriculture) during the 1999–2001 breeding seasons. Habitat restoration efforts primarily converted rowcrop agriculture and pastures into grassland and wetland habitat. Based on land conversion, abundances of most species have likely increased in the area, including many species of management concern. Yet a few species, such as killdeer (Charadrius vociferus), have probably decreased in abundance. This estimation ...
TL;DR: A model for the composition of rodent communities in grass/shrublands of the Southwest and Intermountain West, based on ground cover is proposed, which suggests kangaroo rats are abundant in areas with the most bare soil, Muridae dominate areasWith the most and tallest ground cover, and pocket mice are common in areas of intermediate cover.
Abstract: We live-trapped rodents in 2000–2001 at eight sites on a 3160 ha grassland and mesquite-oak savanna in southeastern Arizona that had been ungrazed since 1968, and on eight paired sites on adjacent cattle ranches. There were 917 captures of 14 species during 5760 trap-nights. Four species of Muridae (Sigmodon fulviventer, Baiomys taylori, Reithrodontomys megalotis and R. fulvescens) were significantly more common on ungrazed plots, while no species was more abundant on grazed plots. However, Heteromyidae as a group (especially Chaetodipus hispidus and Perognathus flavus) comprised a significantly higher proportion of total captures on grazed plots, and heteromyids as a percentage of total captures was positively correlated across all plots with amount of bare ground. One of the eight cross-fence sites also had been trapped in 1981–1983. In the 17 y between trapping events at this site: (1) the grass canopy on both grazed and ungrazed plots had become dominated by taller species, (2) a kangaroo rat...
TL;DR: In this paper, the authors investigated the relationship between canopy closure, shrub cover and the use of coarse woody debris as a travel path by eastern chipmuns in the north central United States.
Abstract: We investigated relationships between canopy closure, shrub cover and the use of coarse woody debris as a travel path by eastern chipmunks (Tamias striatus) in the north central United States. Fine scale movements of chipmunks were followed with tracking spools and the percentage of each movement path directly along coarse woody debris was recorded. Availability of coarse woody debris was estimated using line intercepts. We predicted that, if chipmunks used coarse woody debris to reduce their risk of predation, movement along coarse woody debris would be greater for animals tracked at sites with open canopies and thick shrub cover. Travel along coarse woody debris was negatively associated with canopy closure and positively associated with the percent of coarse woody debris available at a site and the percentage of shrub cover at a site. Sex and age of eastern chipmunks did not appear to influence the amount of use of coarse woody debris. Our results suggest that coarse woody debris is more impor...
TL;DR: In this article, the role of texture, slope and ecosystem age in controlling carbon and nitrogen sequestration in tallgrass prairie topochronosequence was evaluated. And the bottom line is that significant C sequestration was not achieved, given the current level and types of restoration management, within two and a half decades following conversion of cropland to prairie.
Abstract: Prairie restoration has the potential to sequester nitrogen (N) and atmospheric carbon (C) in the soil, but the capability of a site to respond positively to prairie restoration depends on numerous factors such as soil parent material, topography and time. Soil bulk density in the top 10 cm and C and N concentrations at several intervals to a depth of 1 m were measured in a tallgrass prairie topochronosequence at fine- and coarse-textured soil locations to evaluate the role of texture, slope and ecosystem age in controlling C and N sequestration following cessation of cultivation and subsequent prairie restoration. Soil C and N concentrations, contents and C:N ratios were significantly greater in fine-textured soils compared to sites with coarse-textured soil. Soil texture generally did not explain variations in the amounts or rates of C and N sequestration in the restored prairies. Soil surface bulk density was significantly correlated with slope, but not ecosystem age, at sites with coarse-textured soil. Within the limits of this study, neither slope nor ecosystem age were correlated to bulk density at sites with fine-textured soil. Soil C content in the top 25 cm increased significantly as ecosystem age increased for the restored and remnant prairies at the fine-textured location, but not at the coarse-textured location. Results demonstrate that a combination of soil parent material, topography and time since cessation of cultivation control the content and accumulation of C and N following prairie restoration. In the context of this study, the bottom line is that significant C sequestration was not achieved, given the current level and types of restoration management, within two and a half decades following conversion of cultivated cropland to prairie.
TL;DR: Dispersers may play a key role in bobwhite population dynamics whereby declining populations escape extinction through recruitment from productive populations, and no relationships between nest success and dispersal distance were found, suggesting that dispersaldistance had little influence on reproductive output of bobwhites.
Abstract: Movements and dispersal distances are fundamental aspects of ecology and evolutionary biology. Northern bobwhites (Colinus virginianus) generally are considered the least mobile of all gallinaceous species, but dispersal events of bobwhites (commonly referred to as “shuffling”) are well known. Although dispersal may be a key component in regulating population densities and inbreeding avoidance, few studies have attempted to explain relationships between dispersal, mortality and nest success in northern bobwhites. To examine these relationships, we monitored 957 radio-marked bobwhite from 1991 to 1996. Mean dispersal distance did not differ between sexes (P = 0.699). Mean dispersal distances of adults (2821 m) were shorter than those of juveniles (3411 m; P = 0.042). We found no sex- or age-related differences in survival rates among dispersers and non-dispersers. Despite associated risks with increased movement activity in unfamiliar areas, survival rate was 1.5-times greater for dispersers (Ŝ = ...
TL;DR: In this paper, the authors provide quantitative fire history information from a historically unique region, the oak barrens of the Interior Low Plateau Ecoregion, in southern Indiana.
Abstract: The purpose of this paper is to provide quantitative fire history information from a historically unique region, the oak barrens of the Interior Low Plateau Ecoregion. We sampled 27 post oak (Quercus stellata Wangenh.) trees from the Boone Creek watershed in southern Indiana. The period of tree-ring record ranged in calendar years from 1654 to 1999 and fire scar dates (n = 84) ranged from 1656 to 1992. The mean fire interval for the period 1656 to 1992 was 8.4 y and individual fire intervals ranged from 1 to 129 y. The average percentage of trees scarred at the site was 19% or about 1 in 5 trees sampled. No significant relationship was identified between fire years and drought conditions however, variability in the fire record coincided with Native American migrations and Euro-American settlement periods. Temporal variability in the fire record illustrates not only the dynamic nature of anthropogenic fire regimes but also the importance of humans in culturing presettlement barrens communities.
TL;DR: The results suggest that the linkage of fire and water quality of wetlands is through fire's effect on soils rather than vegetation, and field conditions are very important in determining fire's affect on water quality.
Abstract: Depressional wetlands are a natural feature of the longleaf pine-wiregrass ecosystem on the southeastern Coastal Plain. Fire is an essential part of the longleaf pine forest with prescribed burns occurring at 1–3 y intervals. In 2000 and 2001 we sampled wetlands whose surrounding uplands had been burned and reference wetlands (i.e., no fire) to determine the short-term changes (<1 mo) in surface water quality. In 2000 pH, alkalinity and dissolved inorganic carbon (DIC) were higher in burned wetlands than reference sites based on ranked ANOVA. In 2001 dissolved organic carbon (DOC) and NH4-N were higher in burned wetlands than reference ones. Differences between years suggest that field conditions are very important in determining fire's affect on water quality. To clarify our findings we conducted a laboratory experiment where we looked at changes in water quality when exposed to material (wiregrass, dead pine needles and soil) that had undergone simulated fire (muffle furnace at 340 C for 1 h). ...
TL;DR: In this paper, the authors investigated nest site use of the federally endangered northern flying squirrel (Glaucomys sabrinus coloratus) in southwest Virginia at Mount Rogers National Recreation Area.
Abstract: We investigated nest site use of the federally endangered northern flying squirrel (Glaucomys sabrinus coloratus) in southwest Virginia at Mount Rogers National Recreation Area. In second-growth and old forests, number of nests used by both sexes combined was x = 3.3 ± 0.8 (females n = 3, x = 2.7 ± 0.9, males n = 8, x = 3.7 ± 1.2, overall range = 1–6). Nest site characteristics varied and flying squirrels used a variety of nest types including subterranean structures. We found northern flying squirrels chose larger taller nest trees regardless of nest tree type [red spruce (Picea rubens), n = 3, P = 0.04, deciduous, n = 8, P = 0.02, snags, n = 3, P = 0.01] compared to the available trees of the same type within a 200 m2 area of the nest tree. Nest sites in old forest stands (i.e., ≥125 y old) were characterized by greater downed wood (% cover/ha) that can be associated with the increased density of fungal colonies, lower snag density (n-snags/ha) that means a more open midstory for clearer gli...
TL;DR: In unburned dry-mesic sand prairies, an increase in the alien grasses Bromus inermis and Poa pratensis was accompanied by a decline in the native grasses Schizachyrium scoparius and Stipa spartea, and the forbs Echinacea pallida, Helianthus rigidus and Coreopsis palmata.
Abstract: Few data are available that compare long-term changes in burned and unburned prairie remnants in the eastern part of the tallgrass prairie region. To assess effects on species richness and composition, in 1996 we resampled three dry and four dry-mesic sand prairie remnants that were originally sampled in 1976. Three of these sites were managed with burning over the 20 y period and four were not, allowing a comparison of temporal change among burned and unburned sites. Mean richness of native species per plot increased only in burned sites and declined only in unburned sites. In contrast, richness of alien species increased only in unburned sites and declined only in burned sites. In unburned dry-mesic sand prairies, an increase in the alien grasses Bromus inermis and Poa pratensis was accompanied by a decline in the native grasses Schizachyrium scoparius and Stipa spartea, and the forbs Echinacea pallida, Helianthus rigidus and Coreopsis palmata. Railroad rights-of-way prairies bordering agricultural fields were most vulnerable to invasion of alien grasses. These findings underscore the need to use fire to prevent invasion of alien grasses and to maintain native species richness and composition of prairie.
TL;DR: Today's forests have smaller trees and higher tree densities than forests in the presettlement era, and widespread logging, altered fire regimes and other anthropogenic disturbances since European settlement have interacted with physical factors to produce today's forests.
Abstract: General Land Office survey records of 1838–1846 were used to reconstruct the pre-European settlement vegetation along a soil moisture gradient in the Huron National Forest of northeastern lower Michigan. These data were compared to current forest data. Jack pine (Pinus banksiana), red pine (P. resinosa) and white pine (P. strobus) dominated fire-prone presettlement dry and dry-mesic sites on coarse-textured soils of glacial outwash plains and moraines. Hemlock (Tsuga canadensis), beech (Fagus grandifolia), sugar maple (Acer saccharum) and white pine were most important on presettlement mesic sites on medium-textured soils of moraines and kame and kettle topography. Presettlement wet-mesic sites were dominated by hemlock, white pine and aspen (Populus spp.). White cedar (Thuja occidentalis) and tamarack (Larix laricina) dominated presettlement wet sites on organic soils of outwash plains. Important presettlement forest types included: jack pine (41%), mixed conifer–northern hardwood (22%), lowland...
TL;DR: In this article, the authors examined association of pipistrelle occurrence based upon landscape-level variables and cave structure and found that hibernating eastern pipistrelles showed a significant preference for cave openings with east-facing aspects and significantly avoided caves on steep slopes during winter.
Abstract: The eastern pipistrelle (Pipistrellus subflavus) is considered one of the most common and widely distributed species of bats in eastern North America, but little published information exists on its natural history. During surveys of numerous small caves in northwest Arkansas, we documented use by eastern pipistrelles and recorded ambient temperature readings in all caves and at roost and hibernation sites for individual bats. Using presence/absence data and a GIS system, we examined association of pipistrelle occurrence based upon landscape-level variables and cave structure. Hibernating eastern pipistrelles showed a significant preference for cave openings with east-facing aspects and significantly avoided caves on steep slopes during winter. These patterns appear to be due to the influence of cave ambient temperature. Significantly more eastern pipistrelles were found in caves with a wide range of temperature regimes within a season, but with little temperature variation between seasons. In our...
TL;DR: In this article, the effects of strip-discing or prescribed burning on vegetation structure and composition and soil erosion in fescue (Festuca arundiacea) dominated CRP fields in Mississippi.
Abstract: Since 1985 considerable expanses of highly erodible cropland have been enrolled in the Conservation Reserve Program (CRP). Areas enrolled in CRP provide wildlife habitat; however, habitat quality and specific resources on these sites vary in relation to seasonal biological processes of target wildlife species, planted cover and vegetation succession. Throughout the southeastern United States habitat quality for early successional species, such as northern bobwhite (Colinus virginianus), may decline as CRP grasslands age. Although disturbance may enhance and maintain habitat quality for bobwhite, concerns regarding perceived conflicts between wildlife habitat and soil erosion objectives of the CRP persist. During 1995 and 1996 we evaluated effects of strip-discing or prescribed burning on vegetation structure and composition and soil erosion in fescue (Festuca arundiacea) dominated CRP fields in Mississippi. Fall discing generally increased percentage bare ground and plant diversity and decreased ...
TL;DR: Estimates of subdivision between specially sampled populations separated by no more than 10 km indicated effective panmixia at the local level in the central region, historically high rates of localized dispersal in the southwestern Ozarks with recently imposed isolation and dominance of drift at all spatial scales in the northeastern Ozarks.
Abstract: Surprisingly few studies have empirically compared genetic variation between central and peripheral populations of vertebrates, even though such populations are considered very important to evolutionary theories of anagenetic and cladogenetic change. This study assesses levels of microsatellite variability within and between populations of eastern collared lizards (Crotaphytus collaris collaris) sampled in three regions: the central part of its range and at the northeastern periphery in the southwestern and northeastern Ozarks. As expected, central populations possessed significantly higher within-population variability than peripheral populations, whereas the two peripheral subregions did not differ significantly from one another. Estimates of subdivision (Fst) differed significantly among all three regions in the following order: central < southwestern Ozark region < northeastern Ozark region. Estimates of subdivision between specially sampled populations separated by no more than 10 km indicat...
TL;DR: Examination of the effects of isolation and site size on the abundance, density, emigration and immigration of the butterfly Parnassius smintheus in a series of sub-alpine meadows found that individuals-area relationships defined over meadow area showed patterns of decreasing butterfly density with increasing meadows area, indicating that multiple mechanisms can produce decreasing populationdensity with increasing area.
Abstract: We examined the effects of isolation and site size on the abundance, density, emigration and immigration of the butterfly Parnassius smintheus in a series of sub-alpine meadows. Site size was measured either as habitat area or as number of host plants within each meadow. This distinction allowed us to test the hypothesis that population density measured over area (a generalized individuals-area relationship) should tend to decrease with increasing area due to inclusion of more ‘non-habitat’ in larger areas. In general, area measured either as meadow area or host plant abundance explained little deviance in butterfly abundance or movement. Immigration increased with the connectivity (the inverse of isolation) of meadows. We found that individuals-area relationships defined over meadow area showed patterns of decreasing butterfly density with increasing meadow area. This pattern was partially generated by a trend for host plant density to decrease with increasing meadow area. However, this trend wa...
TL;DR: Seasonal dietary patterns from 81 fecal samples collected from black ratsnakes in eastern Ontario supported the hypothesis that black Ratsnakes prey on birds opportunistically, and predation patterns on birds and mammals suggest that ratsnake are opportunistic predators.
Abstract: Black ratsnakes (Elaphe obsoleta obsoleta) prey extensively on both birds (eggs and nestlings) and mammals. There is conflicting evidence, however, regarding whether the snakes specialize on birds during the birds' nesting season or whether predation on birds is opportunistic. We tested these alternatives by determining seasonal dietary patterns from 81 fecal samples collected from black ratsnakes in eastern Ontario over 4 y. We also used these data to determine how diet varies with snake size. Birds occurred in the snakes' diet from May through August, but the occurrence of birds never exceeded that of mammals in any month. This pattern was the same as that previously reported for black ratsnakes in Kansas and supports the hypothesis that black ratsnakes prey on birds opportunistically. Relative to smaller individuals, larger ratsnakes preyed on larger species of mammals and reduced their consumption of smaller species of mammals. The reduction in the consumption of small prey by large snakes wa...
TL;DR: The analysis of the General Land Office (GLO) survey records of the Ashley County, Arkansas, area were analyzed for natural attributes including forest composition and structure, prairie communities and aquatic and geomorphological features.
Abstract: The General Land Office (GLO) survey records of the Ashley County, Arkansas, area were analyzed for natural attributes including forest composition and structure, prairie communities and aquatic and geomorphological features. Almost 13,000 witness trees from at least 23 families were extracted from the surveys. Most (68% of the total) witness trees were black oak (Quercus velutina), pine (Pinus spp.), post oak (Q. stellata), white oak (Q. alba), hickory (Carya spp.) and sweetgum (Liquidambar styraciflua), with 60% of the taxa having fewer than 20 individuals and 26% represented by a single tree. Witness trees were usually moderate sized with very few small or large individuals noted. The distribution of presettlement grasslands, bottomland forests and upland mixed pine/hardwood forests was approximately mapped across the study area. Catastrophic disturbances mentioned in the GLO records included windthrow, floods, fire, timber harvest and earthquakes. Even during this early period, European settlers were altering the Ashley County landscape with trails, homes, farms, cotton gins and small-scale land clearing. Other notable ecological features in these survey records included large woody debris, wetlands, unique terrain conditions and wild game.
TL;DR: It is concluded that small quantities of habitat structure have significant positive effects on macroinvertebrate abundance and diversity in the James River during winter, and habitat structure promotes macroinVertebrate colonization and retention by increasing habitat diversity.
Abstract: We used an experiment and regression analyses to quantify effects of spatial variation in habitat structure abundance on a riverine macroinvertebrate community under winter conditions. Concrete slabs (0.21 m2; n = 24) with different numbers of stones (mean individual stone surface area = 6.44 cm2) attached to upper faces were placed in the James River and retrieved after 28 d. Macroinvertebrate abundance and taxonomic richness on slabs were significantly positively related to stone abundance. Total macroinvertebrate abundance and abundance of oligochaetes (Nais spp.), Asiatic clams (Corbicula fluminea), caddisflies (Leptoceridae), riffle beetles (Elmidae) and stoneflies (Strophopteryx sp.) were linearly related to stone abundance. However, nonlinear relationships occurred between stone abundance and macroinvertebrate taxonomic richness and between stone abundance and abundance of dragonflies (Erpetogomphus sp.), caddisflies (Hydropsychidae), chironomids (Eukiefferiella spp.), mayflies (Ephemerell...
TL;DR: Significantly more individuals of painted turtles occurred in lakes and open waters than in marshes or small ponds, and the opposite was true for Blanding's turtles (Emydoidea blandingii).
Abstract: We sampled a variety of wetlands in the Nebraska sandhills at Valentine National Wildlife Refuge. Significantly more individuals of painted turtles (Chrysemys picta) occurred in lakes and open waters than in marshes or small ponds, and the opposite was true for Blanding's turtles (Emydoidea blandingii). Besides this marked difference in habitat use, 46% of the captured E. blandingii in pond/marsh habitat were juveniles, but only 31.6% in lakes and open water. Current information suggests that marshes and small ponds are important habitat for juvenile turtles, especially Emydoidea blandingii.
TL;DR: The size and sex-age composition of beaver colonies in Illinois, the reproductive potential of female beavers in these colonies and the efficacy of night-vision surveys versus removal trapping for estimating colony size were investigated.
Abstract: Beavers (Castor canadensis) exhibit wide variations in colony composition and demographics over their broad geographic range, so regional population studies are important for sound management of this species. The objectives of this study were to investigate the: (1) size and sex-age composition of beaver colonies in Illinois, (2) reproductive potential of female beavers in these colonies and (3) efficacy of night-vision surveys versus removal trapping for estimating colony size. We harvested and aged 239 beavers (128 males:111 females) during the 1999–2000 and 2000–2001 trapping seasons. The average colony contained 5.6 beavers. Family groups consisting of a breeding pair and at least 1 offspring composed 86% of these colonies; the other 14% consisted of only a breeding pair. Samples of beavers harvested by commercial trappers were skewed towards yearlings and 2-y olds relative to samples taken from trapped-out colonies. Fetal rates were 3.0, 3.4 and 4.2/female for yearlings, 2-y olds and older a...
TL;DR: Simulated leaf herbivory significantly stimulated effluent production on EFN glands of seedlings from both genotypes, but there were no significant differences in EFN activity between genotypes or nutrient treatments.
Abstract: We conducted a pot experiment examining the effects of simulated leaf herbivory and supplemental soil nutrients on extrafloral nectary (EFN) glands of Sapium sebiferum seedlings derived from native Chinese and invasive Texas seed stock. We predicted that simulated herbivory and increased soil nutrients would increase EFN activity. We also predicted that Chinese genotypes would have greater EFN activity than Texas genotypes. Simulated leaf herbivory significantly stimulated effluent production on EFN glands of seedlings from both genotypes, but there were no significant differences in EFN activity between genotypes or nutrient treatments.