Showing papers in "American Midland Naturalist in 1999"
TL;DR: Tallgrass prairie sites subjected to 10 y of annual burning, mowing, nitrogen fertilization or phosphorus fertilization and untreated reference sites were studied to examine effects of these management practices on arbuscular mycorrhizal (AM) symbiosis.
Abstract: Tallgrass prairie sites subjected to 10 y of annual burning, mowing, nitrogen (N) fertilization or phosphorus (P) fertilization and untreated reference sites were studied to examine effects of these management practices on arbuscular mycorrhizal (AM) symbiosis. Spring burning of native prairie field plots significantly reduced AM fungal species diversity, while increasing spore abundance. This increase in total spore number was due to a general increase in most of the 17 fungal species present. In general, the management treatments had larger effects on the richness component of diversity than on the evenness of AM species abundances. Burning and mowing had no significant effects on AM fungal colonization of roots or extraradical mycorrhizal hyphae (EMH) development. However, nitrogen fertilization significantly increased root colonization and EMH development, and P amendment decreased EMH development. There was no significant effect of fertilizer amendment on AM spore abundance, fungal species d...
140 citations
TL;DR: It is believed that most mammals treat forest remnants as habitat patches rather than islands, and that mechanisms such as habitat selection, constraints due to home range size and differential dispersal ability best explain the observed distributions of mammals.
Abstract: We surveyed the nonvolant mammals in 10 forest fragments embedded in a matrix of row crop agriculture in east-central Illinois to assess the impact of forest fragmentation on mammalian diversity and distributions. A total of 19 species were recorded during our study, including 16 native species that occur naturally in forest habitat. We found a significant species-area relationship and a significantly nested subset structure. In particular, gray squirrels, chipmunks and flying squirrels were only encountered in the larger, more continuous sites suggesting a negative effect of habitat fragmentation. Seven species were ubiquitous and we believe that several others occur periodically at all study sites, indicating that most mammalian species currently present have not had their distributions altered by changes in the intervening habitat. Though an analogy to oceanic islands may apply for some species, we believe that most mammals treat forest remnants as habitat patches rather than islands, and that...
121 citations
TL;DR: Neither the Plant Stresshypothesis nor the Plant Vigor Hypothesis can explain responses of all phytophages on a particular plant species.
Abstract: Previous studies of insect-plant interactions have produced the contradictory Plant Stress Hypothesis (that stressed plants are more suitable hosts for phytophages) and Plant Vigor Hypothesis (that vigorous plants are more suitable hosts for phytophages). However, experimental studies of phytophage responses to host stress have involved only one, or a few, related phytophagous species, not whole communities of organisms associated with a particular plant species. We evaluated responses of various arthropods associated with creosotebush Larrea tridentata to manipulated water availability and plant stress in southern New Mexico during 1990–1991. Of 44 arthropod groups (taxa or functional groups) evaluated in our study only two taxa (including a lepidopteran folivore) showed significant negative response to water availability, thereby supporting the Plant Stress Hypothesis. Ten taxa (including eight phytophages) responded positively to water availability, supporting the Plant Vigor Hypothesis. One p...
83 citations
TL;DR: The current population age structure indicated that colonization likely occurred by a series of small dispersal events, and the population remained small for about ten years and then increased dramatically, presumably due to the seed reproduction of the early colonizers.
Abstract: The invasive shrub Lonicera maackii (Rupr.) Herder (Amur honeysuckle) dominates the understory of many deciduous forests in southwestern Ohio and other areas. Extensive sampling of an isolated population of L. maackii was used to elucidate its colonization of a forest woodlot and subsequent growth and development. The current population age structure indicated that colonization likely occurred by a series of small dispersal events. The population remained small for about ten years and then increased dramatically, presumably due to the seed reproduction of the early colonizers. Young prereproductive shrubs are characterized by rapid height growth and high stem recruitment. After shrubs become reproductive at age 5–8, height growth continues but basal stem recruitment is reduced and radial growth increases shrub basal area. Allocation of primary production apparently shifts from stem recruitment and height growth in young shrubs to a balance of height growth, radial expansion and reproduction in ol...
74 citations
TL;DR: In this article, the authors measured oak density and species composition within a longleaf pine-wiregrass (Aristida stricta Michaux) dominated landscape subjected to frequent cool-season fires for 70 years.
Abstract: Fire and soil moisture gradients are thought to influence oak community structure in longleaf pine (Pinus palustris Mill.) woodlands. To explore these influences, we measured oak density and species composition within a longleaf pine-wiregrass (Aristida stricta Michaux) dominated landscape subjected to frequent cool-season fires for 70 yr. At 64 locations within the Joseph W. Jones Ecological Research Center in southern Georgia, oak trees, saplings and regeneration (seedlings plus sprouts) were counted in nested plots, and 20 additional measurements were taken to assess physical and chemical properties of soils, disturbance, density of other vegetation and topography. Principal components analysis of soil data revealed a soil moisture and soil chemistry gradient. Trees and saplings were sparse (mean of 37 and 81 per ha) and most common in dry and dry-mesic sites, while regeneration was abundant (mean of 110,100 stems per ha) and well-distributed across the soil moisture gradient. Fifty percent or...
70 citations
TL;DR: This paper conducted telephone interviews with wildlife professionals to obtain observations of non-native red foxes outside the historical range of the native Sierra Nevada red fox (V. v. necator).
Abstract: Predation on endangered species by nonnative red foxes (Vulpes vulpes) and the resulting controversy over red fox control efforts in California prompted our investigation of the introduction and range expansion of the red fox in California. Since the late-1800s, nonnative red foxes have been introduced into California by escaping from fur farms and fox hunters, through intentional releases by pet owners and fur-farm owners and translocations of previously introduced foxes. From 1990–1993 we conducted telephone interviews of wildlife professionals to obtain observations of nonnative red foxes outside the historical range of the native Sierra Nevada red fox (V. v. necator). Nonnative red foxes now occur throughout lowland areas of California including the Sacramento and San Joaquin valleys, San Francisco Bay-Delta area, the southern California Coast Range and Coastal Plain and most major urban areas. Their range expansion over the last 100 y was the result of population growth from numerous points ...
61 citations
TL;DR: Yellow-flowers plants received more pollinator visits and had more flowers foraged per plant visit than did white-flowered plants, and the addition of sweet-smelling methyl benzoate or spicy methyl cinnamate neither stimulated nor deterred bumblebee visits to either flower color.
Abstract: We examined the roles of floral scent and color in attracting bumblebees (Bombus spp.) to snapdragon flowers (Antirrhinum, Sonnet cultivar). Corolla color differences covaried with differences in floral scent emissions in two inbred lines of snapdragon. White-flowered plants emitted methyl cinnamate, a scent compound not produced by yellow flowered plants, but lacked methyl benzoate, one of the major floral volatiles of the yellow-flowered line. Qualitative scent differences between the two lines were eliminated by applying the complementary scent compounds to filter paper wicks placed within the corollas. Laboratory analyses were performed using gas chromatography-mass spectrometry to verify appropriate modification of floral scents by this method. Two randomized arrays of control and scent-augmented flowers were visited by freely-foraging bumblebees in subalpine meadows in Colorado. Overall, yellow-flowered plants received more pollinator visits and had more flowers foraged per plant visit than...
55 citations
TL;DR: Ingestion improved germination only for persimmon seeds consumed by raccoons, but tree species may realize other benefits from dispersal by coyotes and raccoon (e.g., decreased parental competition).
Abstract: The effect of ingestion by coyotes (Canis latrans) and raccoons (Procyon lotor) on seed germination was investigated for four tree species in Illinois. The germination rate of persimmon (Diospyros virginiana) seeds ingested by raccoons was significantly higher than the rate for uningested seeds. Both were significantly higher than the rate for coyote-ingested seeds. Among coyote-ingested seeds, germination rates of persimmon were significantly higher when seeds were protected by undigested fruit pulp or intact seed sheaths thus reducing the exposure of seeds to gastrointestinal enzymes. American plum (Prunus americana) seeds ingested by coyotes had a significantly lower germination rate compared to uningested seeds, whereas germination of pawpaw (Asimina triloba) seeds was similar between coyote-ingested and uningested seeds. Germination was significantly lower for hackberry (Celtis occidentalis) seeds ingested by raccoons compared to uningested seeds. Ingestion improved germination only for pers...
55 citations
TL;DR: Early primary successional vegetation in 111 small self-contained depressions (potholes) on Mount St. Helens was sampled and the mean richness was 8.8 species and mean cover was 2.6%.
Abstract: How vegetation develops from a source of potential species remains poorly understood. I explored whether colonizing species assemble randomly, or if local deterministic factors alter species establishment to create consistent vegetation patterns. Early primary successional vegetation in 111 small self-contained depressions (potholes) on Mount St. Helens was sampled. Mean richness was 8.8 species and mean cover was 2.6%. Mean percent similarity (PS) between potholes was 46%. A nearby grid of 100 contiguous 100 m2 quadrats on a level barren plain was sampled for comparison. Barren quadrats had mean richness of 12.2 species, mean cover of 1.4% and mean PS of 63%. Pothole vegetation was much more variable than that of the barrens. Canonical correspondence analysis revealed a slight relationship between environmental factors and pothole vegetation. Species composition, cover and species rank orders were predicted extremely well by a stochastic model based on observed frequencies and random accumulatio...
54 citations
TL;DR: Investigating effects of cattle grazing on desert rodent relative abundances, home range sizes and microhabitat use in salt desert shrub communities of the western Great Basin Desert showed that cattle, by preferentially feeding on certain plants, can create conditions that are more suitable for some species of rodents, while reducing important microhabitate for other species.
Abstract: Cattle grazing has been shown to alter various features of desert communities that may impact microhabitats required by various species of desert rodents, with unknown implications for desert rodent communities. We conducted a series of studies at heavily and lightly grazed sites to investigate effects of cattle grazing on desert rodent relative abundances, home range sizes and microhabitat use in salt desert shrub communities of the western Great Basin Desert. Monitoring of rodent populations with repeated live trapping showed that different levels of grazing were associated with differences in relative abundances of some species of rodents. Specifically, Dipodomys merriami was significantly more abundant in heavily grazed areas, and Perognathus longimembris was significantly more abundant in lightly grazed areas. Our studies showed that cattle, by preferentially feeding on certain plants, can create conditions that are more suitable for some species of rodents, while reducing important microhab...
52 citations
TL;DR: Cubic spline analysis indicated that mortality was strongly concentrated among the smallest and perhaps youngest nesting females and was distinctly nonlinear, consistent with the suggestion that the minimum threshold of maturation size was influenced by the size at which the probability of predation decreases.
Abstract: Differential survivorship within or between stages is an important component of most explanations of turtle reproductive patterns. We tested the null hypothesis that a sample of adult female Trachemys scripta found killed by predators was a random sample of adult females found nesting at a site in W-central Illinois by comparing plastron lengths of the two samples. Mean plastron length of 19 dead female T. scripta was significantly smaller than mean plastron length of 79 females found alive. Apparently smaller females were at greater risk of mortality than were larger ones. Cubic spline analysis indicated that mortality was strongly concentrated among the smallest and perhaps youngest nesting females and was distinctly nonlinear. This finding was consistent with the suggestion that the minimum threshold of maturation size was influenced by the size at which the probability of predation decreases.
TL;DR: Rafinesque's big-eared bat (Corynorhinus rafinesquii) is a species of concern throughout much of its range, with limited information available on the life history of this rare bat.
Abstract: Rafinesque's big-eared bat (Corynorhinus rafinesquii) is a species of concern throughout much of its range, with limited information available on the life history of this rare bat. We tracked patterns of population size, measured roost temperatures and used radiotelemetry to locate foraging areas of C. rafinesquii inhabiting a sandstone cave, which these bats used as both a hibernaculum and a maternity site. Counts of hibernating C. rafinesquii ranged from 14–49, with summer colony size reaching a maximum of 118 bats. Bats roosted in different rooms of the cave in winter and summer. Temperatures in a room used in winter were consistently cooler and less stable than temperatures in the room used as the maternity site. Size of foraging areas ranged from 61.6–225.3 ha, and distance of foraging areas from the roost varied from 0.12–1.22 km. We detected no bat >2.5 km from the roost of capture. Bats foraged along ridgelines supporting upland oak-hickory forest.
TL;DR: The results suggest the area of grassland tracts influences the perception of habitat suitability by area-sensitive species more than size or configuration of management units within tracts.
Abstract: We documented the occurrence of 12 bird species within Prairie Ridge State Natural Area, Jasper County, Illinois, a matrix of nine grassland tracts (range 7–120 ha, totaling 489 ha), from 1994 to 1997 and analyzed the presence of these species relative to the area of the nine grassland tracts. Grassland tract area was correlated with the occurrence of greater prairie-chickens (Tympanuchus cupido) (P = 0.016), upland sandpipers (Bartramia longicauda) (P = 0.012), savannah sparrows (Passerculus sandwichensis) (P = 0.009) and Henslow's sparrows (Ammodramus henslowii) (P = 0.005). Minimum area requirements varied from 12 ha for grasshopper sparrows (Ammodramus savannarum), 55 ha for northern harriers (Circus cyaneus), 65 ha for greater prairie-chickens and upland sandpipers, to 75 ha for Henlsow's and savannah sparrows. Therefore, grasslands larger than 60 ha may be required to attract nine breeding grassland bird species. Each grassland tract was divided into 2- to 6-ha management units (mode = 2.8 ...
TL;DR: In this paper, twelve belt transects were used to sample woody vegetation in a 110-y-old regrowth forest on a natural levee ridge bordering Bayou Sauvage, Orleans Parish, Louisiana.
Abstract: Twelve belt transects were used to sample woody vegetation in a 110-y-old regrowth forest on a natural levee ridge bordering Bayou Sauvage, Orleans Parish, Louisiana. Elevation was measured along each transect and species flood tolerances, based upon measured elevational ranges, were assessed. Codominant native hardwoods included Celtis laevigata, Quercus virginiana and Salix nigra; palmetto (Sabal minor) was the principal understory species. An invasive exotic species, Sapium sebiferum, was found throughout the study site (2485 adults >2 m tall per ha), and showed high flood tolerance. Among saplings (0.3–2 m tall), S. sebiferum abundance (3916 per ha) far exceeded that of all native species combined. The forest showed complex species zonation along an elevational gradient of 163.5 cm across a forest-marsh ecotone. Correspondence analysis delimited at least three plant communities, two dominated by single woody plant species and a third with 15 species. These communities were: (1) a Salix nigra ...
TL;DR: It is suspected that the altered temperature regime is also disrupting the gametogenic cycle of all mussels, including at least six federally listed endangered species occurring in the Cumberland River, and will disappear unless they are translocated or the thermal regime returned to normal.
Abstract: Reproduction of Megalonaias nervosa (Rafinesque, 1820) has not been documented for over 20 y in much of the Cumberland River, where water temperatures have decreased and flow regimes have been greatly altered by hypolimnetic discharges from impoundments. Studies in other streams have implicated low temperatures or changes in discharge patterns as causative factors inhibiting reproduction. Megalonaias nervosa were collected from the Cumberland River, translocated to the Tennessee River, and held in an embayment of Kentucky Lake. After the first and second y, samples of M. nervosa were taken from the Cumberland River, an existing population in Kentucky Lake, and the translocated group. Histological examination indicated that translocated mussels had a high incidence of hermaphroditism, and like mussels originating in Kentucky Lake, had undergone an otherwise normal reproductive development. Individuals functioning successfully as females from the translocated group had mature glochidia in their mar...
TL;DR: The results indicate that Argiope trifasciata do not alter size of stabilimenta in response to recent foraging gain alone, and factors other than food intake are involved.
Abstract: This study investigates how recent foraging gain affects the web-building behavior of the garden spider, Argiope trifasciata, especially stabilimentum-building. Adult female spiders in the field and in cages were randomly assigned to two groups, fed and unfed. Spiders in the fed group received three grasshoppers each day; spiders in the unfed group received no prey. The experiment was terminated after each A. trifasciata had built four consecutive webs; the number of days required by each spider was recorded. During the experiment I recorded silk length, catching area, mesh size and stabilimentum area of each web spun by test spiders. Continuously fed, field and caged spiders decreased silk output and web size, increased mesh size and increased the interval between successive foraging bouts. Unfed, caged spiders increased silk output and web size, maintained mesh size and shortened the interval between successive foraging bouts. Although unfed spiders in the field exhibited the same trend, change...
TL;DR: In this article, ground-layer vegetation on 150 plots in Facus-Acer saccharum/Arisaema Mesic Slope and Quercus alba-Alba-saccharum and Parthenocissus Dry-Mesic SLope forests was sampled to determine how the understory of these forests responded to forest management.
Abstract: Between 1993 and 1995 we sampled ground-layer vegetation on 150 plots in Facus-Acer saccharum/Arisaema Mesic Slope and Quercus alba-Acer saccharum/Parthenocissus Dry-Mesic Slope forests to determine how the understory of these forests responded to forest management. Four different stand types, clear-cuts (2–12 ha), group-selection openings (0.1–1.6 ha), single-tree selection openings (0.005–0.013 ha) and uncut 80–100 y-old reference stands were sampled. There was little relationship between the percent cover of most ecological species groups and opening age or size on either mesic or dry-mesic slopes. While clear-cuts and group-selection openings had significantly greater cover of several ecological species groups (used to classify mesic and dry-mesic slopes) than reference stands, single-tree selection openings did not differ significantly from reference stands in the cover of any ecological species group. Pearson correlation analysis indicated that more ground-layer species were significantly c...
TL;DR: It is concluded that changes in macroinvertebrate community structure probably were related to the increased substrate complexity provided by zebra mussels.
Abstract: Zebra mussels, Dreissena polymorpha, increase macroinvertebrate abundance on hard substrata in lakes and large rivers because they enhance surface area, substratum heterogeneity and the accumulation of benthic organic matter (BOM). We tested the hypothesis that zebra mussel colonization of hard substrata in a lake-outlet stream would similarly increase macroinvertebrate abundance. Zebra mussels were attached to artificial rocks (0.05 m2) in a crossed factorial design with two states of mussels (live or dead) and three densities [low (200·m−2), medium (500·m−2) or high (1000·m−2)] plus a noncrossed control (no attached mussels). Rocks were placed in an erosional zone of a lake-outlet stream in southwestern Michigan that contained low densities of zebra mussels. After 28 d total macroinvertebrate abundance was significantly higher on rocks with high densities of zebra mussels, but live or dead treatment had no effect on macroinvertebrate abundance. Family richness differed significantly among densi...
TL;DR: Future value of food affects the foraging behavior of squirrels through the balancing of present and future needs, and some properties of caching in the context of a food's future value are explored.
Abstract: Food storage in animals allows foragers to reap when food is plentiful and costs are low and eat when food is scarce and costs are high, thus shifting resources from periods of low value or high availability to periods of high value or low availability. To a caching animal, a food item has two components: its present value for immediate consumption and its future value if stored. We explored some properties of caching in the context of a food's future value using free-living fox squirrels (Sciurus niger) and manipulations of cacheability of supplemental food. We assessed squirrel behavior using giving-up densities (GUDS) of noncacheable food in artificial food patches. Squirrels had higher GUDs in assessment trays when given noncacheable supplemental food than when food was not augmented; when given supplemental food in a highly storable form, squirrels had intermediate GUDs. Thus, future value of food affects the foraging behavior of squirrels through the balancing of present and future needs.
TL;DR: Assessment of the distributions and selected aspects of the life histories and habitat associations of these crayfishes showed that O. peruncus was more widespread and more abundant than O. quadruncus, and patterns of reproductive events in the species' annual life cycles were similar, although O.peruncus showed signs of mating activity a month earlier than o.quadruncus.
Abstract: The crayfishes Orconectes peruncus and O. quadruncus are endemic to the upper St. Francis River drainage in southeastern Missouri, and were classified as threatened in a recent analysis of the conservation status of crayfishes in the United States and Canada. Their distributions are not documented and little is known about their ecologies. In addition, recent collections suggested that the introduced crayfish O. hylas may be displacing O. quadruncus from its type locality, Stouts Creek (Madison and Iron counties). The purpose of our study was to assess and compare the distributions and selected aspects of the life histories and habitat associations of these crayfishes. Sampling at 57 sites on 30 streams in the upper St. Francis River drainage from October 1996 through March 1998 showed that O. peruncus was more widespread and more abundant than O. quadruncus. The two species were sympatric in only three streams. Patterns of reproductive events in the species' annual life cycles were similar, alth...
TL;DR: Oogenesis followed a pattern similar to that of typical spermatogenesis, with smallest average oocyte size observed in August, andGamete release occurred between late winter-early spring (March) and midsummer (July).
Abstract: Quadrula metanevra were collected monthly from Pickwick Dam tailwater (Tennessee River mile 201.3), Tennessee, between July 1988 and June 1990. A total of 227 specimens were examined. The population consisted primarily of dioecious individuals (98%) and had an unequal sex ratio (1.5 female: 1 male). Histological examinations showed that typical spermatogenesis began in autumn (September), increased in spring (March–April), and continued until midsummer (July). Atypical spermatogenesis predominated during July and August, and may have increased the number of sperm produced in autumn and winter. Oogenesis followed a pattern similar to that of typical spermatogenesis, with smallest average oocyte size observed in August. Gamete release occurred between late winter-early spring (March) and midsummer (July). Brooding females were found between late March and July.
TL;DR: Flower color change, floral rewards, and the size of a floral display in relation to pollinator attraction were studied in Aster vimineus to determine that variation in disk color was due to localized color change from yellow to red.
Abstract: Flower color change, floral rewards, and the size of a floral display in relation to pollinator attraction were studied in Aster vimineus. The center disk florets of A. vimineus are either all yellow or all red in a given flower. We determined that this variation in disk color was due to localized color change from yellow to red. Yellow florets contained more pollen and a greater percentage of viable pollen than red florets. All pollinator types consistently preferred flowers with yellow disks over those with red disks. The addition of nectar did not influence pollinator visitation rates, unless the pollinators were choosing only among flowers with red disks. Retention of the flowers with red disks allowed for greater floral display which increased pollinator visitation rates.
TL;DR: Nocturnal mammalian and avian predators of deer mice often use sound to locate their prey, and mice rustling in hardwood leaf litter should be more easily detected, so deer mice restrict their movements to routes that reduce the risk of auditory detection by predators.
Abstract: The influence of predation risk on microhabitat selection in male adult deer mice (Peromyscus maniculatus) was examined using an enclosure experiment. The relative amount of time spent by the deer mice on coniferous leaf litter, hardwood leaf litter and logs was measured. Mice preferred dry coniferous litter over dry hardwood litter, but had no preference when both litter types were wet. Deer mice traveled more along logs placed on hardwood litter than on coniferous litter. Nocturnal mammalian and avian predators of deer mice often use sound to locate their prey, and mice rustling in hardwood leaf litter should be more easily detected. Therefore, deer mice restrict their movements to routes that reduce the risk of auditory detection by predators.
TL;DR: The results suggest that frequent burial of sundews, with its disproportionate effects on juvenile mortality, selects for rapid growth and establishment in nutrient-poor wet savannas.
Abstract: Although chronically low soil fertility is widely recognized as an important selection pressure on carnivorous plants, the effects of other potentially important selection pressures, such as natural disturbances, have largely been ignored. In this study, I examined the effects of fire and removal of live plants and litter on seedling establishment of Drosera capillaris (pink sundew), a small insectivorous plant common to wet, nutrient-poor pine savannas of the southeastern United States. I also examined the effects of soil disturbances associated with crayfish burrows on mortality. Fires occurring during the winter of 1996/1997 increased the density, growth and establishment of seedlings during the growing season of 1997. In addition to fires, local removal of established plants and their associated litter greatly increased seedling density and growth within savannas. The proportion of rosettes that flowered at sites not burned recently (>1 year before) was nearly twice that at sites burned more ...
TL;DR: Despite widespread evidence of high nutrient and sediment loading from agriculture and other human activities in the upper Susquehanna basin since at least 1965, it is found that little change in unionid populations between the two time periods is found.
Abstract: In 1955–1965, the streams and rivers of the upper Susquehanna River basin in New York were surveyed for unionid mussels. We resurveyed unionid populations at the same sites in 1996–1997 to determine whether populations had declined and whether declines could be correlated with inputs of sediments and nutrients from agriculture, which have been thought to be major threats to imperiled unionid populations in North America. Despite widespread evidence of high nutrient and sediment loading from agriculture and other human activities in the upper Susquehanna basin since at least 1965, we found little change in unionid populations between the two time periods. The range of Alasmidonta varicosa contracted while that of Lampsilis cariosa expanded. Overall species richness and the ranges of the other nine species were unchanged. Six species in the basin were formerly listed as Category 2 species or are now considered “Species at Risk” by the United States Fish and Wildlife Service. Of these, Alasmidonta u...
TL;DR: Although bison may have less impact upon stream communities than previous studies of cattle impacts have shown, differences in climate and stocking rate could be important factors.
Abstract: The distribution and diversity of macroinvertebrates in relation to bison crossings was studied for four seasons in a headwater reach of a tallgrass prairie stream. Species richness was significantly higher above crossings only during the fall. Summer samples revealed significantly higher EPT (richness within only Ephemeroptera, Plecoptera and Trichoptera) index values above crossings than at crossings. On average, over 10% more fine sediment (<0.2 mm) occurred at the crossings than above or below crossings. Densities of two taxa (Hydropsyche spp. and Elmidae) were significantly higher above or below crossings, whereas three taxa (Bezzia/Palpomyia spp., Culicoides sp., and Naididae/Tubificidae) were significantly higher at crossings for at least one season. Overall, this study suggests that impact of bison on benthic communities of headwater streams was spatially limited. Although bison may have less impact upon stream communities than previous studies of cattle impacts have shown, differences in...
TL;DR: Vegetation interspersion, patch evenness, plant richness and total area were most important in explaining abundance of waterfowl, waterbirds, neotropical migrants and woodpeckers, respectively.
Abstract: Beaver ponds are a widely distributed and abundant wetland resource in the southeastern United States, but their value as avian habitat is poorly documented. We sampled bird populations at six South Carolina Piedmont beaver ponds from April 1993 through June 1994 to examine seasonal community composition and discern microhabitat variables that are associated with bird group abundance and richness. The resident/short-distance migrant group and the neotropical migrant group were most abundant in the spring seasons and waterbirds were least abundant. In fall and winter the resident/short-distance migrant group was most abundant at all ponds with the exception of one pond in winter, which had very high use by waterfowl. Seasons were generally most important in predicting bird species richness and abundance of the resident/short-distance migrant group. Vegetation interspersion, patch evenness, plant richness and total area were most important in explaining abundance of waterfowl, waterbirds, neotropic...
TL;DR: Suitable host fishes were identified for two species of freshwater mussels from the Coosa River drainage, Mobile Basin: Lampsilis altilis, the fine-lined pocketbook and Villosa vibex, the southern rainbow, which display highly modified mantle margin lures in the early spring.
Abstract: Suitable host fishes were identified for two species of freshwater mussels (Unionidae) from the Coosa River drainage, Mobile Basin: Lampsilis altilis, the fine-lined pocketbook and Villosa vibex, the southern rainbow. Suitable hosts are defined as fishes that produce juvenile mussels from glochidial infestations in the laboratory. Larvae of both L. altilis and V. vibex transformed successfully on four species of sunfishes (Centrarchidae): Lepomis cyanellus, Micropterus coosae, M. punctulatus and M. salmoides. For both mussel species transformation success on L. cyanellus was highly variable and generally lower than on Micropterus spp. Gravid female L. altilis and V. vibex display highly modified mantle margin lures in the early spring. In addition to displaying mantle lures, L. altilis produce superconglutinates, similar to those recently described for three other species of Lampsilis in the southeastern U.S.
TL;DR: It is shown that a large portion of the seed bank remains ungerminated under natural disturbances, and the age and history of the component seeds may influence the regenerative function of seed banks in natural ecosystems.
Abstract: Although much is known about variation in both seed bank composition and disturbance effects in temperate deciduous forests, understanding of how these components interact to determine the importance of seed banks to regeneration is limited. To examine the interactive influences of seed bank composition and postdisturbance environment on seed bank recruitment, a seed bank transplant experiment was conducted in a disturbed temperate zone deciduous forest in eastern Pennsylvania. On average, 75% of the seed bank remained ungerminated. This was mainly the result of failed germination by alien species. The postdisturbance environment differed in its influence or the two dominant species, Rubus allegheniensis and Phytolacca americana. Whereas R. allegheniensis recruitment did not differ between postdisturbance environments, significantly more P. americana seedlings emerged under more open conditions. Different proportions of P. americana seeds germinated from the two seed bank sources. These results s...
TL;DR: In this article, the authors compared bird use of riparian buffers along main stem rivers, tributary streams, and reference riparian zones having intact, upslope forests.
Abstract: Retention of riparian buffers is a common management practice used to protect streams from the effects of upslope forest harvest. We compared bird use of riparian buffers along main stem rivers, tributary streams, and reference riparian zones having intact, upslope forests. Community composition differed considerably between buffers and references, and also between main stems and tributaries. Density of the more common species (those detected >20 times) was significantly higher along main stems than along tributaries. Four species (bay-breasted warbler, black-throated green warbler, blue jay, Cape May warbler) were more abundant along main stems than along tributaries; no species was more abundant along tributaries. The overall density of less common species was significantly higher in buffer strips than in reference sites, but four of the more common species (bay-breasted, blackburnian, black-throated green, and Cape May warblers) were more abundant in reference sites than in buffer strips. We d...