Showing papers in "American Midland Naturalist in 1998"
TL;DR: In this paper, the authors used a large database on local stream fish assemblages and species distributions in the Interior Highlands of Arkansas to test three macroecological hypotheses: (1) faunal similarities among upland river basins can be predicted from the hierarchical geographical connectivities of those streams in the larger Mississippi River Basin drainage network; (2) local (within-site) species richness increases in proportion to regional (basin) richness.
Abstract: There has been strong recent interest in the “macroecological” approach of explaining local community phenomena as a consequence of patterns at larger geographic scales. Various authors have suggested that if local observations can be explained by the larger-scale patterns in which they are embedded, there is less need to invoke local (within-site) processes (like competition, habitat structure, etc.) to explain community structure. We used a large database on local stream fish assemblages and species distributions in the Interior Highlands of Arkansas to test three macroecological hypotheses: (1) faunal similarities among upland river basins can be predicted from the hierarchical geographical connectivities of those streams in the larger Mississippi River Basin drainage network; (2) faunal richness of drainages up to the size of small rivers (ca. 4000 km2) increases with drainage area; and (3) local (within-site) species richness increases in proportion to regional (basin) richness. These hypoth...
114 citations
TL;DR: In this article, the authors describe massive autumn migrations of dragonflies (Odonata) which occurred at Chicago, Illinois (14 September 1978), Cape May, New Jersey (11 September 1992), and Crescent Beach, Florida (3-5 September 1993).
Abstract: We describe massive autumn migrations of dragonflies (Odonata) which occurred at Chicago, Illinois (14 September 1978), Cape May, New Jersey (11 September 1992), and Crescent Beach, Florida (3–5 September 1993). Estimated numbers of migrant dragonflies involved in these flights were approximately 1.2 million, >400,000, and 200,000, respectively. We also document other recent observations of large swarm migrations of dragonflies in eastern North America, review previous reports of this phenomenon, and compare these events to the flights at Chicago, Cape May and Crescent Beach. Records of large dragonfly migrations show several distinct patterns: (1) all reports fell between late July and mid-October, with a peak in September; (2) most of the large flights occurred along topographic leading lines such as coastlines and lakeshores; (3) massive swarm migrations generally followed the passage of synoptic-scale cold fronts; and (4) the common green darner (Anax junius) was the principal species involve...
113 citations
TL;DR: The distribution and abundance of amphibians and reptiles in forest stands subjected to salvage cutting and prescribed burning were compared with their unmanaged counterparts as discussed by the authors, showing that hardwood had the most distinctive herpetofaunal community of the four stands.
Abstract: The distribution and abundance of amphibians and reptiles in forest stands subjected to salvage cutting and prescribed burning were compared with their unmanaged counterparts. The study was conducted on the Atlantic coastal plain at Chesapeake Farms near Chestertown, Maryland. Three herpetofaunal trapping arrays were systematically located in each of four forest stand types: hardwood (Hardwood), cut-over hardwood (Cut), mixed pine-hardwood (Pine) and prescribed burn pine (Burn). A total of 3931 individuals representing 29 species were captured in 30,540 trap nights during the spring and summer 1992 and 1993. Felling of hardwoods and prescribed burning of pine resulted in similar responses from the herpetofaunal communitites; Hardwood had the most distinctive herpetofaunal community of the four stands. Adults and young-of-the-year (YOY) of six amphibian species were significantly more abundant in Hardwood than Cut. Only one amphibian species, Pseudacris triseriata, was less abundant in Hardwood th...
100 citations
TL;DR: Removal of fruit pulp from seeds by frugivores was critical for germination, especially for seeds within the lipid-rich fruits of Lindera and Viburnum, which suggests that for some fruiting plants, frugiva provide an essential service by freeing seeds from fruit pulp, in addition to their role in seed dispersal.
Abstract: Coevolutionary models of the interactions between fruiting plants and avian seed dispersers have been influenced by the assumption that regurgitation and defecation of seeds have diffferent effects on seed coats, and consequently seed germination. We evaluated how the manner of seed processing affects seed germination by feeding fruits of three bird-dispersed shrubs, spicebush (Lindera benzoin), chokecherry (Prunus virginiana), and arrowwood (Viburnum dentatum), to captive cedar waxwings (Bombycilla cedrorum) and thrushes (Turdus migratorius, Hylocichla mustelina, Catharus guttatus and C. minimus). Cedar waxwings defecate all seeds, whereas thrushes regurgitate most seeds. For all three shrub species and all five bird species, there were no differences in germination success between seeds manually cleaned of pulp, and cleaned, bird-passed seeds, regardless of whether seeds were regurgitated or defecated. However, seeds of Lindera and Prunus that were defecated by cedar waxwings and planted with f...
88 citations
TL;DR: In this paper, the distribution limits of L. maackii in these two directions were correlated with differences in landscape structure, such as the percentage of forest land and degree of forest connectivity.
Abstract: The Asian shrub Lonicera maackii (Rupr.) Herder has been widely used as an ornamental in the eastern United States. First planted in Oxford, Ohio, around 1960, it has since spread into forest patches in the surrounding agricultural landscape. Despite its abundance, and its bird-dispersed fruits, the spread of Lonicera maackii has been unequal in different directions, with local distribution limits much farther N than W of Oxford. Our objective was to determine whether the distribution limits of L. maackii in these two directions were correlated with differences in landscape structure: percentage of forest land and degree of forest connectivity. Aerial surveys were used to determine the current distribution of L. maackii in forest patches in a belt transecting N and W from Oxford. The N transect, which had more extensive spread of L. maackii, had greater forest cover and connectivity. In both transects, L. maackii reached its distribution limit when forest cover dropped to <5% and forest connectiv...
84 citations
TL;DR: The authors compared species composition patterns between pre-European and present periods for a portion of the Georgia piedmont that had a systematic presettlement land survey and identified a primary gradient that distinguishes between the vegetation of these periods on the basis of habitat moisture preferences and fire tolerance of species.
Abstract: Due to the extensive removal of the forest cover of the southeastern piedmont during the 19th century and to the lack of systematic presettlement records for most of this region, there has been little basis for relating the piedmont's maturing postsettlement secondary forest to its pre-European condition. This study compares species composition patterns between pre-European and present periods for a portion of the Georgia piedmont that had a systematic presettlement land survey. Detrended correspondence analysis of presettlement, immature postsettlement, and mature postsettlement forests identifies a primary gradient that distinguishes between the vegetation of these periods on the basis of habitat moisture preferences and fire tolerance of species. A secondary gradient emphasizes life history characteristics of species that typically differentiate immature and mature postsettlement forests; presettlement forests were not dominated by the late successional species typical of mature postsettlement...
81 citations
TL;DR: It is suggested that high mortality of unionids can occur between 4 and 6 yr after initial invasion by dreissenids or up to 8 yr depending on water current patterns, which is higher over a larger area than that measured in other rivers to date.
Abstract: To assess the impact of zebra and quagga mussel (Dreissena spp.) infestation on unionids, unionids (Bivalvia: Unionidae) were sampled in the Detroit River in 1982–1983, before mussels invaded the river, and in 1992 and 1994, after mussels invaded the river. Live unionids at four stations along the southeastern shore accounted for 97% (20 species) of all shells collected in 1982–1983, whereas live unionids accounted for only 10% (13 species) in 1992. A similar decline in live unionids occurred at nine stations along the northwestern shore, except the decline occurred over the three sampling periods: in 1982–83, 84% (22 species) were live; in 1992, 65% (26 species) were live; and, in 1994, only 3% (13 species) were live. The difference in time to near-total mortality of unionids along the southeastern and northwestern shores is attributed to differences in the time of invasion and abundance of zebra mussel veligers in distinct water masses emanating from Lake St. Clair located immediately upstream ...
80 citations
TL;DR: In this paper, the effect of an engineered flow disturbance on macroinvertebrates in an intermittent N Texas stream was studied and the authors found that woody debris is an important refuge and source of recolon...
Abstract: We studied the effect of an engineered flow disturbance on macroinvertebrates in an intermittent N Texas stream. To augment a drinking water supply, water is being diverted through the natural stream channel. Quantitative sampling of sediments and woody debris was conducted immediately before water diversion, immediately after and periodically during recovery, for three diversion events over a 2-yr period. Reduction in total density of macroinvertebrates was dependent on type of substrate, averaging 76% in sediments as compared with 66% on woody debris. Recovery was rapid for most taxa, which often reached predisturbance density in less than 1 mo. For the entire macroinvertebrate assemblage in 1992 and chironomids only in 1991, resilience was greater on woody debris than on sediments. Compared with sand, the common inorganic substrate in this stream, woody debris was more stable, due in part to its retention by debris dams. It appears that woody debris is an important refuge and source of recolon...
75 citations
TL;DR: Structural features surrounding latrines often are important travel routes or foraging areas for various small vertebrates and the visitation of mammals and birds to sites exhibiting these structural features may result in infection with B. procyonis, which could have long-term impacts on populations of native mammal and birds.
Abstract: Baylisascaris procyonis, the common large roundworm of raccoons (Procyon lotor), causes clinical neurologic disease in many species of mammals and birds. Infective eggs of B. procyonis are present at raccoon latrine sites, and these sites may be important in the transmission of this parasite to syntopic small vertebrates in forested areas. We located raccoon latrines in forested sites in Indiana, sampled soil and fecal material from these locations, and examined these samples for the presence of Baylisascaris procyonis eggs. We also quantified the structural characteristics of raccoon latrines in wooded areas, compared their characteristics with randomly located sites, and classified sites based on structural features using stepwise discriminant function analysis. B. procyonis eggs were present at 14% of the raccoon latrines sampled. Latrine sites differed from randomly located sites and exhibited characteristics generally associated with treefall gaps. Most latrines were located either on logs (...
71 citations
TL;DR: Tiger beetle larvae are physiologically capable of surviving several days of inundation during floods without mechanisms to prevent burrow flooding by entering a quiescent state and survive much longer periods of anoxia than has been previously reported for terrestrial insect larvae.
Abstract: The sedentary terrestrial larvae of the tiger beetle, Cicindela togata, inhabit areas that are often flooded for days or weeks. We tested the ability of these larvae to survive immersion and anoxia. Maximum survival time of immersed, anoxic C. togata was 6 days at 25 C. Time to 50% mortality (LT50) in these conditions was 85.9 ± 23.5 h. Survival times were more than eight times longer than those of similarly treated larvae of Tenebrio molitor (LT50 10.1 ± 3.2 h). Similar or somewhat longer survival times were observed in larvae of C. togata exposed to an anoxic nitrogen atmosphere (LT50 102 ± 31 h) and of T. molitor (LT5014.4 ± 6.5 h). At 10 C, LT50 of C. togata in anoxic atmospheres exceeded 10 days. Tiger beetle larvae are physiologically capable of surviving several days of inundation during floods without mechanisms to prevent burrow flooding. By entering a quiescent state, C. togata larvae survive much longer periods of anoxia than has been previously reported for terrestrial insect larvae.
70 citations
TL;DR: It was demonstrated several ways that vector behavior can influence rates of disease spread in natural populations, including bumblebees and moths preferentially visited healthy flowers, but the strength of this preference declined if the bees had prior exposure to diseased flowers.
Abstract: Anther-smut disease caused by Ustilago violacea is transmitted by insects that visit diseased flowers and then deposit spores on healthy Silene alba plants. The transmission rate of this disease therefore depends on spore deposition by the vector species and preferences for infected vs. healthy hosts. We observed natural populations of S. alba to document the most abundant insect visitors, which include syrphid flies, andrenid bees, bumblebees and a variety of nocturnal moths. Using bumblebees and moths in flower preference studies, we showed that bumblebees preferentially visited healthy flowers, but the strength of this preference declined if the bees had prior exposure to diseased flowers. Nocturnal moths showed less discrimination with respect to disease status when plants were arranged in a field population of S. alba, and preferentially visited plants with more flowers. A laboratory analysis of spore deposition by bumblebees showed that whereas most spores were deposited on the first severa...
TL;DR: Although most insectivorous bats do not prey on mosquitoes, these insects were a consistent component of the diet of Indiana bats and were eaten most heavily during pregnancy and also during lactation.
Abstract: Dietary preferences of Indiana bats were determined by analyzing 382 fecal pellets collected beneath roost trees in southern Michigan, over parts of 3 yr. Although terrestrial insects (Lepidoptera and Coleoptera) usually dominated the diet of Indiana bats in more southern states, those in Michigan consumed mostly insects associated with aquatic environments. Indiana bats in Michigan ate primarily Trichoptera (55.1% of volume) and Diptera (25.5%), followed by Lepidoptera (14.2%) and Coleoptera (1.4%). Consumption of Diptera was highest during lactation (48.2%), whereas consumption of Lepidoptera was least during this time (7.7%). Although most insectivorous bats do not prey on mosquitoes (Culicidae), these insects were a consistent component of the diet of Indiana bats and were eaten most heavily during pregnancy (6.6%).
TL;DR: It is concluded that gray rat snakes perceive relatively distant visual cues from prey, and that nest provisioning (activity localized around a nest) may facilitate snakes correctly choosing to ascend trees that contain active nests and ignoring those that do not.
Abstract: We examined the responsiveness of adult gray rat snakes to avian prey in enclosures that simulated natural habitat conditions. Subjects searched for arboreal nest contents in the presence or absence of a bird model flown so as to simulate avian provisioning behavior. In the absence of the model, gray rat snake latency to capture prey was over 92 % greater than when searching for nest contents with the model. Snakes responded to model flight by turning their heads in the direction of its movement. We conclude that gray rat snakes perceive relatively distant visual cues from prey, and that nest provisioning (activity localized around a nest) may facilitate snakes correctly choosing to ascend trees that contain active nests and ignoring those that do not.
TL;DR: Nine sites in the Neosho River (Kansas) were surveyed for unionid mussels during summer 1994 to compare the effectiveness of quadrat sampling vs. timed snorkel searches for evaluating relative abundance, species richness and diversity, size distribution and evidence of recruitment.
Abstract: Nine sites in the Neosho River (Kansas) were surveyed for unionid mussels during summer 1994 to compare the effectiveness of quadrat sampling vs. timed snorkel searches for evaluating relative abundance, species richness and diversity, size distribution and evidence of recruitment. At each site, timed snorkel searches were conducted in a 100-m stretch, 10-m wide, of wadable habitat. Mussels were returned to their original location following identification and sizing. Next, 40 1 m2 quadrats were sampled from the same stretch. Finally, 15 qualitative substrate samples (approximately 1 m2) were sieved in an attempt to detect recruitment. A total of 786 mussels were caught during 12 h, 11 min of snorkel searches compared to 896 mussels from 360 1-m2 quadrats. Quadrula metanevra was the most abundant species collected by either qualitative or quantitative methods. Differences in assessments of species diversity and relative abundance between methods were not significant; however, timed searches reveal...
TL;DR: It is determined that inexpensive and easily maintained amphibians and exotic fishes could act as hosts for two species of native North American unionid mussels, and bypass the need to identify native hosts when the object is to culture mussels.
Abstract: This study determined that inexpensive and easily maintained amphibians and exotic fishes could act as hosts for two species of native North American unionid mussels, and bypass the need to identify native hosts when the object is to culture mussels. Two mussel species, Lampsilis cardium and Utterbackia imbecillis, were used to parasitize 42 exotic fishes and seven potential nonpiscine host species. Nonpiscine hosts included amphibians and decapod crustaceans. Lampsilis cardium successfully metamorphosed on six species of exotic fishes, as well as on larval tiger salamanders. Utterbackia imbecillis successfully metamorphosed on 30 species of exotic fishes and all four amphibian species tested. No glochidia metamorphosed on crustaceans. Successful metamorphosis on amphibians indicates that mussel zoogeography may be more complicated than previously thought. Using surrogate hosts may be a valuable alternative to natural hosts in laboratory culture of mussels.
TL;DR: While captures were diverse, Hymenoptera (mostly ants), Coleoptera and Gastropoda accounted for 69% of the total dry mass caught, and their importance implies that prey sampling methods that do not survey freshly caught prey may seriously underestimate resource availability in pitchers.
Abstract: I examined capture rates of invertebrate prey by pitchers of the purple pitcher plant Sarracenia purpurea, in western Newfoundland, Canada. While captures were diverse, Hymenoptera (mostly ants), Coleoptera and Gastropoda accounted for 69% of the total dry mass caught. Gastropoda decompose quickly and completely in pitchers, and their importance (20%) implies that prey sampling methods that do not survey freshly caught prey may seriously underestimate resource availability in pitchers. The average pitcher caught 11 mg dry mass of animal biomass over its lifetime, but capture rates were highly variable (range 0–67 mg). Pitchers opening earlier in the season caught no more or less than those opening late. Larger pitchers caught more than smaller ones, although size accounted for a small fraction of total variance. Capture rates changed with time, peaking in pitchers 12–33 days old; however, pitchers continued to catch prey through their 2nd season (i.e., after overwintering). In an average pitcher,...
TL;DR: Increases of populations in both disturbed hibernacula suggest M. sodalis is affected by limiting factors other than, or in addition to, human visitation in winter.
Abstract: Overwinter weight loss of Indiana bats (Myotis sodalis) was assessed during the 1989–1990 and 1990–1991 winters at three hibernacula (high, low, and no human visitation) in southern Indiana. We weighed 4264 M. sodalis captured during the autumn swarming and spring emergence periods. Mean spring weights were less than mean autumn weights for males and females in both years. Overwinter weight loss, expressed as a percentage of mean autumn weight, ranged from 15% to 33% and was least at the cave that received no human visitation in three of four sex-year combinations. The magnitude of overwinter weight loss differed among caves in three of four tests, but the effect of cave on weight loss was inconsistent between sexes in both years and between years within sex. Percent weight loss was less at the hibernaculum with low visitation (x = 5.5 visits/winter) than at the hibernaculum with high visitation (x = 378 visits/winter) in two of four sex-year combinations. Increases of populations in both distu...
TL;DR: Some of the most abundant bird species wintering on CRP fields have been undergoing long-term population declines, thus this program has the potential to mitigate population losses.
Abstract: We compared the abundance and species composition of birds in Conservation Reserve Program (CRP) fields with the same aspects in row-crop fields during the winter (January and February) over several years (1992–1995) for six midwestern states (Indiana, Iowa, Kansas, Michigan, Missouri and Nebraska). Field techniques were standardized in all states. CRP fields consisted of either permanent introduced grasses and legumes (CP1) or permanent native grasses (CP2), and the plant species seeded in CRP fields differed within and among states. Vegetation characteristics of CRP fields varied considerably from state to state, but vertical density and total canopy cover (primarily grasses) were particularly high in Nebraska. Mean annual total bird abundance ranged from 0.1 to 5.1 birds per km of transect in CRP fields and from 0.1 to 24.2 in row-crop fields. The total number of bird species recorded in CRP fields in the six states ranged from 6 to 32; the range for row-crop fields was 8 to 18. The most abund...
TL;DR: In this article, the authors assessed shorebird use of artificial wetlands within the Mississippi Alluvial Valley during the winters of 1991-1992 and 1992-1993 and during the autumn of 1994.
Abstract: We assessed shorebird use of artificial wetlands within the Mississippi Alluvial Valley during the winters of 1991–1992 and 1992–1993 and during the autumn of 1994. On agricultural fields managed to provide habitat for waterfowl from November to March, mean shorebird density was 58.6 birds/100 ha, but shorebird densities were greater on soybean fields than on rice or moist-soil fields. Killdeer (Charadrius vociferus) and common snipe (Gallinago gallinago) were common throughout winter, but shorebird abundance and species richness along survey routes increased from November through April. During the late summer and autumn, wetlands on public lands in the Mississippi Alluvial Valley are managed by the U.S. Fish and Wildlife Service specifically to provide foraging habitat for shorebirds. From August through October 1994, we observed 14,564 individual shorebirds of 22 species using these anthropogenic wetlands. Mean shorebird density on wetlands managed by flooding previously dry, disked fields was ...
TL;DR: The Buffalo Ridge Wind Resource Area poses little threat to resident or migrating birds at its current operating level as discussed by the authors, and birds abundance peaked in spring in both 1994 and 1995, when red-winged blackbirds (Agelaius phoeniceus), mallards (Anas platyrhynchos), common grackles (Quiscalus quiscula), and barn swallows (Hirundo rustica) were the species most commonly seen.
Abstract: During 1994–1995, we saw 70 species of birds on the Buffalo Ridge Wind Resource Area. In both years bird abundance peaked in spring. Red-winged blackbirds (Agelaius phoeniceus), mallards (Anas platyrhynchos), common grackles (Quiscalus quiscula), and barn swallows (Hirundo rustica) were the species most commonly seen. Most birds (82–84%) flew above or below the height range of wind turbine blades (22–55 m). The Buffalo Ridge Wind Resource Area poses little threat to resident or migrating birds at its current operating level.
TL;DR: The severe disturbance increased the abundance of early successional woody species and of herbaceous genera that tolerate open habitats, such as Erichtites, Phytolacca, and Erigeron.
Abstract: To document how species richness and diversity (H′) recover from severe large-scale disturbance, we report temporal patterns of species composition and diversity following grass-to-forest succession from a long-term experiment in the Coweeta Basin, western North Carolina. The original experiment—clear-cutting, 5 yr of grass cover followed by a herbicide treatment, and abandonment in a Southern Appalachian mixed deciduous forest—represents the most severe human disturbance in the Coweeta Basin. For several years after cessation of management, Robinia pseudoacacia quickly sprouted from roots and exceeded the growth rates of other species. Liriodendron tulipifera increased in density and basal area because of its prolific seedling establishment and rapid growth rate. Regeneration of large seeded species was mixed—sparse for Quercus rubra and Q. coccinea and nonexistent for Q. prinus and Q. velutina. In the overstory, density-based H′ increased from 1958, before grass conversion, to 15 yr and 28 yr f...
TL;DR: The role of prairie landscape configuration on the population dynamics and conservation of greater prairie-chickens was explored in this paper, where the authors compared population trends and breeding ecology of birds in prairie mosaic and contiguous prairie landscapes in southwestern Missouri.
Abstract: To better understand the role of prairie landscape configuration on the population dynamics and conservation of greater prairie-chickens, we compared population trends and breeding ecology of prairie-chickens in prairie mosaic and contiguous prairie landscapes in southwestern Missouri. Over 27 yr, the contiguous prairie landscape supported a stable population, whereas the prairie-chicken population in the prairie mosaic landscape declined. In 1986 and 1987, less than one-third of greater prairie-chicken nests occurred in native prairie habitats in the prairie mosaic landscape, but 90% of nests in the contiguous prairie area were in native prairie. Greater prairie-chicken nests established in agricultural habitats had substantially lower nest success than nests in native prairie or mixed native-exotic grass pastures. Nest success was higher in the contiguous prairie landscape than in the prairie mosaic area in 1 of 2 yr. Habitat use by broods differed between the areas: in the contiguous prairie l...
TL;DR: It is hypothesize that this is a positive feedback relationship that has promoted the increase of Formica colonies and allowed them to permanently change the structure and composition of a large portion of the vegetation in this rich fen.
Abstract: The ants Formica podzolica, Myrmica fracticornis and M. incompleta commonly build nests in a large peatland complex in N-central Montana. Nests of Formica are much larger than those of Myrmica spp. and occur in a microtopographic mosaic of hummocks and hollows. The large mound nests of F. podzolica and the hummocks are similar in size, and both had elevated levels of K, PO4−, Mg and Na compared to the peatland surface, suggesting that the hummocks are abandoned ant mounds. Ant mounds provide an environment for plants that has better aeration and is warmer as well as nutrient-enriched. A few species of strongly rhizomatous graminoids occur on active mounds, but abandoned nests (hummocks) provide habitat for larger shrubs as well as many species of plants that otherwise could not grow in the cold, nearly saturated peat. Formica workers obtain much of their nutrition by tending aphids that feed on the shrubs growing on hummocks. We hypothesize that this is a positive feedback relationship that has p...
TL;DR: Growth of black walnut on the low-elevation riparian site was directly and positively influenced by increased streamflow in midwinter and in late summer when subsurface soil moisture recharge from streamflow may be a critical moisture source.
Abstract: Radial growth (indices of tree-ring widths) of Eastern cottonwood (Populus deltoides Marsh.), a flood-tolerant species, and black walnut (Juglans nigra L)., a flood-intolerant species, were compared with climate and streamflow data by stepwise multiple regression for a riparian forest along the Olentangy River in central Ohio to investigate: (1) the influence of these variables on riparian primary productivity; and (2) whether these species can be used as predictors for the reconstruction of streamflow. Black walnut showed a significant growth response to streamflow. There was no relationship between growth of Eastern cottonwood and streamflow. Growth relationships with climate (mean monthly air temperature, total monthly precipitation) and Palmer Drought Severity Index (PDSI) showed black walnut growth on an upland riparian site was more sensitive to temperature and PDSI than on a lower-elevation site. Growth of black walnut on the low-elevation riparian site was directly and positively influenc...
TL;DR: In this article, the authors characterized 131 summer, diurnal bed sites of 26 elk (11 bulls and 15 cows) in Custer State Park, South Dakota, from 5 June-30 August 1994, 1995 and 1996.
Abstract: We characterized 131 summer, diurnal bed sites of 26 elk (11 bulls and 15 cows) in Custer State Park, South Dakota, from 5 June–30 August 1994, 1995 and 1996. Overstory canopy closure, number and basal area of trees, percent litter and bare ground were greater (P 0.05). Trees were present at 128/131 (97.7%) of bed sites (0.01 ha square plot), but occurred on only 41.2% (54/131) of random plots. An average summer, diurnal elk bed site had basal area >12.4 m2/ha, >110 trees/ha, >54% canopy closure on N aspects. Overstory canopy closure, tree basal area and microsite temperature correctl...
TL;DR: Total invertebrate densities, as well as densities of three taxa, were significantly greater on smooth wood than on smooth plexiglass, indicating that inorganic substrates are less suitable as sites of attachment and/or food source than similar wood substrates.
Abstract: In a field experiment, I examined the effect of wood hardness, condition, texture and substrate type on colonization of stream invertebrates and resulting community structure. Bundles of wood differing in hardness (firm and soft), condition (conditioned and unconditioned), and texture (rough and smooth) were placed in a Michigan stream and colonized for 30, 61 and 91 days. In addition, plexiglass rods were used as an inert analog of wood. Taxa richness was significantly greater on (1) rough-conditioned wood vs. rough-unconditioned wood and (2) smooth wood vs. smooth plexiglass. Larval Chironomidae were numerically dominant on all substrates and their density was affected by the interaction between wood condition and time, as well as wood condition and wood hardness. Densities of four of the six most abundant taxa were significantly greater on rough-soft wood than rough-firm wood. Densities of two taxa were significantly greater on rough-conditioned wood than rough-unconditioned wood. Wood texture...
TL;DR: Although results varied on a metal-specific and species-specific basis, liming was overall successful in reducing metal concentrations in old-field plant species.
Abstract: Concentrations of heavy metals in old-field plant species were compared among untreated reference subplots, unlimed sludge-treated subplots and limed sludge-treated subplots during the 4th yr of ecosystem recovery following long-term (11-yr) nutrient enrichment. Although results varied on a metal-specific and species-specific basis, liming was overall successful in reducing metal concentrations in old-field plant species. For example, concentrations of Cd in leaves and roots and concentrations of Pb and Zn in roots of Ambrosia trifida were significantly lower in plants collected from limed compared to unlimed sludge-treated subplots. Liming significantly reduced concentrations of Cd in leaves and roots of Solidago canadensis, and in the leaves, roots, and seeds of Setaria faberii to levels found in untreated reference subplots. Liming also significantly reduced concentrations of Cu in the roots of Solidago canadensis, Pb in the roots and seeds of Setaria faberii, and Zn in the roots and leaves of...
TL;DR: It is concluded that despite the short distances slugs are likely to disperse seeds, their generalist habits and ubiquity suggest that they may have complex and ecologically significant effects on seed dispersal in Pacific Northwest forests.
Abstract: We observed wild banana slugs (Ariolimax columbianus) eating fruits of several Pacific Northwest plant species. Slime trails and direct observations indicated that slugs are capable of reaching the fruits of many wild plants. This motivated us to test the hypothesis that slugs may act as seed dispersers, provided that they defecate viable seeds. We fed captive slugs the fruits of Rubus spectabilis, R. discolor, Vaccinium ovatum, V. parvifolium, Gaultheria shallon and Disporum smithii to determine the effects of slug ingestion on seed germination. At least some seeds of each species germinated after the fruits were consumed by the slugs, but the effects on germination were species-specific. Seeds of Rubus spectabilis were less likely to germinate after passage through the guts of slugs, and we found significant evidence that the two fruit color morphs reacted differently over time. Disporum smithii seeds did not statistically differ in germination behavior between treatments, although the trend su...
TL;DR: Ant-plant asociations were more frequent during the warm, humid months, when weather conditions are milder, most plants are producing new vegetative growth, many are in flower or fruit and other insects increase their activities, suggesting that ants can diversify their foraging activities.
Abstract: We quantified the frequency and seasonal variation of ant-plant associations mediated by plant-derived food sources, and the intensity of their use by ants. Thirteen ant species and 42 plant species were related in 135 pairs of associations. The plant families Leguminosae and the Cactaceae were those most visited by ants. The ants Camponotus rubrithorax (28 species) and Crematogaster opaca (16 species) used the most plant species as food sources. No obligatory ant-plant associations were found. Ant species studied did not use all food resources available to them, resulting in a significant differential choice of food resources; using nectar from plant reproductive structures and floral nectar more and extrafloral nectar less. Ant-plant asociations were more frequent during the warm, humid months, when weather conditions are milder, most plants are producing new vegetative growth, many are in flower or fruit and other insects increase their activities. Thus, ants can diversify their foraging activ...
TL;DR: In this article, the influence of specific types of habitat structure on fish assemblage structure, diversity and abundance in large rivers is largely unknown, and the authors determined whether fish assembls differed among various artificial and natural habitats within the main channel border (shallow, nearshore areas) of the upper Mississippi River, and assessed whether different types of artificial structure influenced fish assembly structure over long (>0.2 km) sections of shoreline habitat.
Abstract: The influence of specific types of habitat structure on fish assemblage structure, diversity and abundance in large rivers is largely unknown. This study determined whether fish assemblages differed among various artificial and natural habitats within the main channel border (shallow, nearshore areas) of the upper Mississippi River, and assessed whether different types of artificial structure influenced fish assemblage structure over long (>0.2 km) sections of shoreline habitat. Daytime electrofishing during August and October 1994 captured 31 different fish taxa from main channel border habitats in Pool 6 of the upper Mississippi River. Nine species of fish preferred specific types of nearshore habitat. Fish abundance and diversity measures differed little among habitat types, but significantly larger fish were present at locations with structure (wing dikes, woody snags) than at sites without (bare shore). Cluster analysis indicated that different fish assemblages occupied different habitat typ...