Showing papers in "American Midland Naturalist in 1997"

Short-term and long-term effects of burning on oak savanna arthropods

Abstract: -We investigated the effects of prescribed burning on the composition, abundance, species richness and diversity of oak savanna arthropod communities in a replicated, large-scale, 30-y experiment. We employed four sampling methods over 3 y and caught 11,215 arthropods of 551 species. Species had varied and often negatively correlated short vs. longterm responses to burning. In the years savannas were burned, species richness and abundance of arthropods, especially Homoptera and Lepidoptera, were reduced and species compositions were sometimes more similar. However, despite its major effect on vegetation, frequency of burning did not affect arthropod abundance and species richness, but sometimes caused savannas to be similar in species or taxonomic order composition. The Shannon diversity index was unaffected by burning. On the whole, prescribed burns necessary to maintain grasslands and savannas do not appear to be harmful to, or to greatly impact, the

Ice storm damage to an old-growth oak-hickory forest in missouri

Abstract: -On 6 December 1994 a severe ice storm hit several midwestern states. We inventoried damage and woody debris input from the storm in 30 0.1-ha permanent plots in an old-growth oak-hickory forest in northern Missouri. Twenty-seven percent of 1386 live trees 22 cm dbh were damaged but only 7% were severely damaged. Basswood (Tilia americana) and American elm (Ulmus americana) were the most susceptible species; white oak (Quercus alba), eastern hophornbeam (Ostrya virginiana) and shagbark hickory (Carya ovata) were among the least susceptible. Damage levels increased with stem diameter, and trees occupying dominant crown positions were more heavily damaged than suppressed trees. Damage severity was highly variable across the landscape, but trees on lower slopes and mesic aspects tended to have more damage, even for a given species. Coarse woody debris input from the storm averaged 5.1 m3/ha, 27% of the prestorm volume, with northern red oak (Q. rubra) and white oak contributing 79% of the total. This single event will probably have minimal impact on stand composition and structure, but repeated ice storms at 20-yr intervals likely influence forest dynamics in midwest oak-hickory forests.

Variation in creosotebush (larrea tridentata) canopy morphology in relation to habitat, soil fertility and associated annual plant communities

Abstract: -Differences in creosotebush (Larrea tridentata) crown morphology may reflect changes in the relative demand for water vs. nutrient resources, coinciding with shrub growth and development. Creosotebushes with inverted cone-shaped crowns were more abundant in water-limited environments whereas hemispherical shaped creosotebushes were more abundant in less water-limited environments. Cone-shaped creosotebushes accumulated substantially less litter under their canopies than did creosotebushes with hemispherical shaped crowns. Soil nutrient concentrations under conical shrubs were similar to those in intershrub spaces and both of these were significantly less than soil nutrient concentrations under hemispherical shrubs. In ecosystems where overland flow of water exerted a greater influence on the movement of organic litter than did wind, shrub shape had little effect on long-term litter accumulation. No persistent differences in the biomass or diversity of ephemeral taxa exploiting undershrub areas were found, probably because the positive effects of greater nutrient resources under hemispherical shrubs were offset by the limitations imposed by the larger, more dense canopies of hemispherical shrubs. Overall, creosotebush morphology affected litter accumulation patterns and soil nutrient patterns, and must be considered when assessing the heterogeneity of desert ecosystems in the southwestern USA.

Comparative Responses of Lonicera Maackii (Amur Honeysuckle) and Lindera Benzoin (Spicebush) to Increased Light

Abstract: -In shadehouses providing 1%, 25%, and 100% of full sun photosynthetic photon flux density (PPFD), we measured growth, acclimation of net photosynthesis (An), and leafand branch-level plasticity of two deciduous shrubs, a nonindigenous species [Lonicera maackii (Rupr.) Herder] and an indigenous species [Lindera benzoin (L.) Blume]. This comparative research assessed potential plant performance in response to modified disturbance regimens that increase light availaiblity. When forest-grown shrubs were moved to conditions of increased light, Lonicera maackii had maximum stem growth at 100% PPFD, higher An in pre-existing leaves, greater acclimation ability in pre-existing leaves, and greater plasticity of stomatal density and branchlevel allocation. Maximum stem growth of Lindera benzoin occurred at 25% PPFD. The inability of this species to use light above 25% PPFD was likely the result of biochemical limitation to carbon capture although relatively greater allocation of energy to roots may have contributed. As canopy thinning and fragmentation increase light availability in disturbed forests, high-resource invasive species such as L. maackii are likely to assume greater importance with concomitant decreases in importance of low-resource species such as L. benzoin.

Presettlement vegetation patterns along the 5th principal meridian, missouri territory, 1815

Abstract: -Data from the original General Land Office (GLO) survey (1815) of the 5th Principal Meridian were used to evaluate presettlement vegetation patterns in eastern Missouri and Arkansas. Data were divided into three physiographic sections: Mississippi Alluvial Plain, Ozark Plateau and Dissected Till Plain. Distances to bearing trees and diameters were used to estimate tree density and to evaluate the relative structure and composition of presettlement vegetation. The Mississippi Alluvial Plain was the most densely timbered physiographic section. White oak (Quercus alba), black oak (Q velutina), sweet gum (Liquidambar styraciflua) and hickory (Carya spp.) had high importance values. Significantly lower tree densities occurred in the Ozark Plateau and Dissected Till Plain. Important components of the Ozark Plateau were shortleaf pine (Pinus echinata), white oak, black oak and post oak (Q stellata). In the Dissected Till Plain, white oak was dominant and black oak, hickory, elm (Ulmus spp.) and sycamore (Platanus occidentalis) were important components. There has been some debate regarding the presettlement structure of timbered lands in the Ozark Plateau. Some biologists argue that closed forest once dominated the Ozarks, whereas others argue the region was once dominated by open woodland. The evidence presented here suggests the Ozark vegetation was, in general, an open woodland landscape in 1815.

Effects of Organic Pollution on an Appalachian Cave: Changes in Macroinvertebrate Populations and Food Supplies

Abstract: -Density of troglobitic crustaceans and levels of potential food sources were compared in reference pools and pools polluted by septic system effluent in Banners Corner Cave, Virginia. Data from four physicochemical variables indicated slight to high pollution in five pools compared with two unpolluted pools. Polluted pools had high levels of conductivity, nutrients and fecal coliforms. Highly polluted pools also had decreased dissolved oxygen levels. Isopods (Caecidotea recurvata) were absent from highly polluted pools. Highest isopod density (up to 74.6/M2) occurred in slightly and moderately polluted pools. Amphipods (Stygobromus mackini) were absent from all polluted pools. Fungal biomass was negligible in all pools. Bacterial biomass accounted for a greater proportion of sediment total organic matter (TOM) in polluted pools, but there was little overall increase in TOM in polluted pools. Results of a laboratory growth experiment suggest that isopods can use bacteria from septic effluent as a food. However, presence of coarse particulate matter, not organic enrichment by septic system effluent, was the most likely cause of high isopod density in some pools. Septic system effluent may provide additional food to the aquatic community in Banners Corner Cave, but generally was damaging to the system.

Nut caching by blue jays (Cyanocitta cristata L.): implications for tree demography.

Abstract: -We examined jay caching patterns over 3 yr in a woodland-prairie landscape in S-central Iowa. Three aspects were examined: jay habitat preferences for caching, jay caching patterns before and after fire, and the influence of predation on nuts by small mammals on tree recruitment in jay territories. Blue jays cached nuts in a wide range of habitats, from open, grassy patches to mature forest. Jays cached preferentially in regenerating woodland and edge habitats while usually avoiding grassland habitats. Caching increased in grassland following a controlled burn. Detection by small mammals of artificial nut caches placed by the investigator was extremely

Changes in the composition of a ranid frog community following bullfrog extinction

Abstract: -Natural experiments have often shown that lowered competition or predation results in patterns of ecological release, density compensation, or predatory release of target species. At Point Pelee National Park, Ontario, Canada, from 1992 to 1994, we conducted extensive surveys of habitats to document patterns of relative abundance and distribution of amphibians and to compare these patterns with those documented in studies conducted in 1972 and 1991. Bullfrogs (Rana catesbeiana) have not been observed since spring 1990 and are now considered to be locally extinct in the park. Relative abundance of the green frog (R clamitans) has increased 4X since bullfrog extinction. Similarities in the natural history of bullfrogs and green frogs suggest that interactions should be greatest between this pair. The predaceous habits of bullfrogs are well-documented, and the experimental literature suggests that bullfrogs and green frogs are competitors. Changes in the pattern of ranid relative abundance that we observed suggest that the bullfrog is important in structuring amphibian communities.

Microhabitat use and community structure of Darkling beetles (Coleoptera: Tenebrionidae) in shortgrass prairie: effects of season, shrub cover and soil type.

Abstract: -I conducted pitfall-trapping studies from 1992 through 1995 to evaluate the effects of vegetation structure and soil texture on seasonal variation in the distribution, relative abundance and species composition of darkling beetles (Coleoptera: Tenebrionidae) in shrub-dominated areas of shortgrass prairie in N-central Colorado. Numbers of beetles captured in traps placed in shrub, cactus, grass and bare-ground microhabitats were used to assess microhabitat use and diel timing of activity, differences in the relative abundance of beetles between spring and summer and to compare beetle communities on sites with different shrub vegetation and soil types. Beetles were most numerous in summer on all sites, although some species showed peaks of activity in spring. All but two species (Eleodes extricata, E. hispilabris) were captured significantly more often in traps beneath shrubs, underscoring the importance of this microhabitat for thermal cover, food or protection from predators. Further, in shrub-dominated areas, beetles were more nocturnal than had been reported previously for adjacent grasslands, suggesting that shrubs kept temperatures on low-lying areas warmer at night than on open prairie. Fourteen tenebrionid species were captured, and on average, significantly more species were captured beneath shrubs than in other microhabitats. Each site had a suite of five resident species, of which only Eleodes obscura and Embaphion contusum were captured on all sites during all trapping periods. Species richness and beetle abundance, especially of the most common species (Eleodes obscura), were inversely related to shrub cover but were greater in areas with coarsely textured soils. Overall, tenebrionid communities in shrub-dominated areas were similar to those reported for open prairie, but small species tend to predominate in grasslands, perhaps because most refuges are relatively small. The prevalence of larger beetles in areas with sandy soils and large shrubs may be related to the number of suitable refuges, both belowground and in vegetation, as well as the availability of preferred feeding and oviposition sites.

Effects of Urbanization on Brown Trout Salmo Trutta, Other Fishes and Macroinvertebrates in Valley Creek, Valley Forge, Pennsylvania

Abstract: -We determined the effects of urbanization on fish and benthic macroinvertebrate communities of Valley Creek and its tributary, Little Valley Creek, in southeastern Pennsylvania. Brown trout (Salmo trutta) were a major component of the fish community except in the urbanized upstream portions of the watershed. Growth rates and condition factors of brown trout were within the upper range of reported values, indicating high productivity in the nonurbanized portions of the Valley Creek system. In the urbanized portion of the watershed, fish communities and benthic macroinvertebrate communities consisted of pollution-tolerant species (e.g., Semotilus atromaculatus, Lepomis cyanellus, Isopoda) and brown trout were absent. In nonurbanized areas, pollution-tolerant fish and benthos declined while less tolerant species (Salmo trutta, longnose dace; Rhinichthys cataractae, darters; Etheostoma olmstedi, cutlip shiners; Exoglossum maxillingua, and invertebrates such as Amphipoda, Ephemeroptera, and Trichoptera) increased. Regressions of community-level patterns (species richness, diversity, evenness, number of trout, number of age-O trout) vs. watershed physical characteristics (stream order, distance from source, stream discharge, water temperature) differed between the two main branches of the stream (Valley Creek, Little Valley Creek). This indicated that localized factors related to urbanization differentially affected these areas. Dramatic changes in the fish and benthic communities in the most urbanized sections of Valley Creek demonstrated the deleterious impacts associated with increasing urbanization of the watershed.

Antipredator behaviors of newly metamorphosed green frogs (rana clamitans)and leopard frogs (r. pipiens) in encounters with eastern garter snakes (th amnophis s. sirtalis)

Abstract: -Three experiments were conducted on antipredator behaviors of newly metamorphosed green frogs (Rana clamitans) and northern leopard frogs (R. pipiens) in the presence of a common predator, the eastern garter snake (Thamnophis s. sirtalis). Both species engaged in distinctive antipredator behaviors, i.e., crouching and ceasing to move, in the presence of active snakes. These behaviors rendered frogs less likely to be captured. Green frogs were contacted by snakes more frequently than were leopard frogs, but capture rates of individuals that had been contacted were not different between species. Green frogs allowed snakes to approach more closely, and they jumped more frequently upon initial escape, than leopard frogs. Morphological measurements showed that there were no specific differences in snout-vent length, or in snout-vent length/leg length ratios, but that the average leap distance was greater for leopard frogs compared to green frogs. The results supported the hypothesis that leopard frogs use distance from the predator in terrestrial habitats more effectively than do green frogs to avoid predation, which agreed generally with some descriptive field results reported elsewhere.

Hydrologic context and macroinvertebrate community response to floods in an appalachian headwater stream

Abstract: -The response of aquatic macroinvertebrates to two floods was examined in a 2nd-order stream draining a 132-ha watershed on the Fernow Experimental Forest in West Virginia. Floods with recurrence intervals of 18 and 12 yr occurred in February and May 1994. Benthic organic matter and macroinvertebrate abundance and community structure were affected by the floods. Most of the common macroinvertebrate taxa decreased in abundance 70-95% immediately following the February flood. For most physical and biotic variables, recovery to preflood levels was complete before the May flood (42 days) based on preflood levels. Shifts in community structure following floods were small compared to seasonal variation. By August following the May flood, few differences could be detected from August of the previous year. Taxa associated with organic matter accumulations such as leaf packs and organic debris dams were affected less by the February flood than were most riffle taxa; one common leaf pack taxa, Pteronarcys, increased in abundance in riffles following the flood. I attribute the rapid recovery of the benthic community to abundant refugia, including organic debris dams, deep interstitial habitat, and 1st-order tributaries. Analysis of the long-term flow record for the Fernow Experimental Forest suggests that a probabilitybased hydrologic criterion for a flow disturbance is inadequate for Appalachian headwater streams.

Drifting Macrophytes as a Mechanism for Zebra Mussel (Dreissena Polymorpha) Invasion of Lake-Outlet Streams

Abstract: -Veligers spawned from lake populations are thought to be the major means for spread of zebra mussels (Dreissena polymorpha) into outflowing rivers. We hypothesized, however, that adult zebra mussels attached to lake macrophytes could enter outflowing streams by 'rafting' on uprooted macrophytes originating in lakes. Drifting macrophytes were collected on three occasions (8-h, mid-channel, seine samples) from Christiana Creek (the outflow of invaded Christiana Lake, southwestern Michigan). On average, 2620 adult mussels entered the stream per day attached to plants, mostly on wild celery (Vallisneria americana). To measure experimentally the transport of macrophytes, 50 V americana plants were tagged with flagging tape, released and recollected (N = 5 releases). Average transport distance of macrophytes was 333 m, and the presence of attached mussels did not affect transport distance. Woody debris was the most important retention item, entrapping 85% of the released macrophytes. Drift of macrophytes from upstream lakes provides a mechanism by which adult zebra mussels can invade outlet streams, but retention appears to limit downstream transport to relatively short distances. Regardless, high potential survival of adult mussels compared to veligers suggests that adult drift on macrophytes is an important component of riverine invasion.

Growth rate, body size, sexual dimorphism and morphometric variation in four populations of painted turtles (Chrysemys picta bellii) from Nebraska

Abstract: -I studied variation in individual growth rate, body size, sexual size dimorphism and morphometry in two sandhill lake and two Platte River floodplain populations of painted turtles from western Nebraska. Individual growth rate of juveniles and mean adult body size were greater in the sandhills populations than in the floodplain populations. Comparisons of mean individual growth rates of juveniles reported here and mean population egg size reported for these populations in an earlier study support predictions for the evolution of offspring size. Females were larger than males and sexual dimorphism was greatest in populations with relatively slow individual growth rates, a pattern that is inconsistent with the findings for other local populations of painted and closely related slider turtles. Body sizeadjusted carapace width, shell height and plastron length varied significantly within and between sexes and populations. Interpopulational variation in shell width and height are hypothesized to be related to variation in clutch frequency or to differences in hydrodynamics between lake and riverine systems.

Will Conversion of Conservation Reserve Program (CRP) Lands to Pasture Be Detrimental for Grassland Birds in Kansas

Abstract: -The Conservation Reserve Program (CRP) was established by the 1985 Food Security Act (Farm Bill). Unless renewed, most CRP contracts will expire in 1997 and up to 70% of CRP fields in Kansas may be converted to pasture. We compared avian use of CRP areas with that of pasture to determine if such conversion would be detrimental to grassland birds. Data on vegetative structure, avian abundance, and avian reproductive success were collected on five CRP fields and five pastures during summer 1993. Pastures had significantly greater vegetative cover and CRP fields had more bare ground. Vegetation was significantly taller in CRP fields late in the summer. Total avian abundance and that of dickcissels, grasshopper sparrows, meadowlarks, brown-headed cowbirds and upland sandpipers were greater in pastures than in CRP fields. Reproductive success and rates of nest parasitism by brownheaded cowbirds did not differ between the habitats, but nests were more numerous in grazed pastures. If the CRP is not reauthorized in the 1995 Farm Bill and most of the Kansas land currently enrolled in CRP is converted to pasture, the conversion probably will not be detrimental to grassland bird populations if the land is moderately grazed.

Effects of Horning and Rubbing Behavior by Bison (Bison Bison) on Woody Vegetation in a Tallgrass Prairie Landscape

Abstract: -Horning and rubbing behaviors of American bison (Bison bison) and their effects on woody vegetation were investigated for 2 yr on a herd of 300+ animals reintroduced to a 1973-ha tallgrass prairie site in Oklahoma. Horning and rubbing activity was significantly higher in summer than in other seasons. Whether this increase was associated with rut, shedding of winter pelage, insect harassment, or a combination of these factors was unclear; however, these behaviors did have measurable impacts on the woody vegetation of the area. Bison injury to trees was minimal, although one willow (Salix nigra) was uprooted and killed during the study, and several other trees were seriously damaged. Bison horning had the greatest effect on saplings and shrubs, killing or severely damaging 4% of the woody plants documented within the study area and causing moderate injury to 13% and light injury to 12%. Bison showed a strong preference for small willows, killing or severely damaging 17% of the saplings and shrubs of this species during the study. Bison also used artificial, man-made objects present on the landscape such as utility poles and fenceposts. Results suggest that horning and rubbing by bison, along with fire and drought, may have influenced the historical distribution of woody vegetation in prairie environments.

Effects of seed density on germination and establishment of a native and an introduced grass species dispersed by granivorous rodents

Abstract: -Dense aggregations of Oryzopsis hymenoides (Indian ricegrass) and Bromus tectorum (cheatgrass) seeds occur in rodent caches in the Great Basin. Rodent caching behavior may influence establishment and persistence of these two desert grasses. Seed caches of rodents clearly introduce exaggerated seedling competition in these species. Greenhouse experiments were used to determine if establishment and persistence of these species were affected differently by densities of seeds in caches. Germination and establishment of Indian ricegrass, a native perennial grass, were less affected by high seed densities than germination and establishment of cheatgrass, an introduced annual weed. The different natural histories of these species, as well as data presented here, suggest that the high seed densities introduced by caching behavior of desert rodents may be beneficial to Indian ricegrass and harmful to cheatgrass.

Aboveground biomass and net primary production along a Virginia barrier island dune chronosequence.

Abstract: -Aboveground biomass was measured along a chronosequence of dunes on Hog Island, a Virginia Coast Reserve LTER site. The dominant species were Ammophila breviligulata and Spartina patens. Aboveground biomass was harvested monthly from 10 quadrats on 6, 24, 36 and 120-yr-old dunes from April to November 1993. Total aboveground biomass decreased along the chronosequence and ranged from 205 g m-2 on the 6-year-old dune to 152 g m-2 on the 120-yr-old dune in October 1993. Spartina patens biomass exceeded A. breviligulata biomass on the 6, 24 and 36 yr-old-dunes. Spartina patens biomass decreased along the chronosequence; in July it ranged from 72 g m-2 on the 6-yr-old dune to 5 g m-2 on the 120-yr-old dune. Ammophila breviligulata biomass increased from 17 g m-2 on the 6-yr-old dune to 39 g m-2 on the 120-yr-old dune. Ammophila breviligulata had greater biomass than S. patens on only the 120-yr-old dune. Net aboveground primary productivity did not vary along the chronosequence. Aboveground net primary production (ANPP) from the sum of species peaks was 259 g m-2 yr-1 for the 6-yr-old dune, 226 g m-2 yr-1 for the 24-yrold dune, 256 g m-2 yr-1 for the 36yr-old dune and 274 g m-2 yr-1 for the 120-yr-old dune. There was no opportunity to study dunes of the same or comparable ages on other barrier islands, so these inferences apply only to the four dunes studied on Hog Island.

Comparative Analysis of Habitat Selection, Nest Site and Nest Success by Cedar Waxwings (Bombycilla Cedrorum) and Eastern Kingbirds (Tyrannus Tyrannus)

Abstract: -We compared nest success, habitat use and nest site selection of cedar waxwings (Bombycilla cedrorum) and eastern kingbirds (Tyrannus tyrannus) breeding in the same locations over a 3-yr period to determine if nest success differed between species, or with habitat or nest sites. Nest success was lower in waxwings in all 3 yr (3-yr average: 18% vs. 55%). Both species preferred hawthorns (Crataegus) as nest trees, but in neither species was nest success higher when nests were placed in hawthorns. Nest success did, however, vary with habitat structure: successful kingbirds nests were usually located in the most open habitat (i.e., lowest canopy cover and surrounded by the fewest trees), whereas failed waxwing nests were located in habitats with the densest vegetation. Habitats of failed kingbird and successful waxwing nests were intermediate and similar. Nest sites were very similar, except that waxwing nests were much more concealed in the nest tree's vegetation. However, neither cover nor other nest site variables differed between failed and successful nests within either species. A discriminant function analysis that used mainly habitat variables correctly classified 68% of failed waxwing and 64% of successful kingbird nests, but less than 50% of failed kingbird and successful waxwing nests. Thus, kingbirds and waxwings overlap extensively in habitat use and nest sites, but kingbirds prefer more open habitats, presumably because it allows them to detect predators and defend their nests. Waxwings prefer habitats with denser vegetation, presumably because they rely upon inconspicuous behavior to avoid nest predators. Failed kingbird nests were in waxwing-like habitats, suggesting a link between nest sites, habitats and parental behavior. We believe that the characteristic aggressive nest defense of kingbirds was the major reason for their higher nesting success.

Ground beetle (coleoptera : carabidae) activity density and community composition in vegetationally diverse corn agroecosystems

Abstract: -Influences of weeds on activity density (number captured per trap per day), species richness and diversity of carabids (Coleoptera: Carabidae) in reduced tillage corn (Zea mays L.) plantings were examined in a 2-yr field study. Four treatments were examined: corn monoculture, corn with broadleaved weeds, corn with grassy weeds, and corn with a mixture of broadleaved and grassy weeds. Carabids were sampled with pitfall traps every 34 wk from May to September in 1988 and 1989. Neither broadleafed nor grassy weeds significantly influenced carabid activity density in 1988, a year of severe drought. However, in 1989, a year of normal rainfall, activity density was significantly greater in broadleaved weed treatments. Activity density of each of the major carabid species was affected differently by the treatments. Weedy vegetation in corn plantings generally did not have significant effects on carabid species richness, and community similarity was generally high for all treatments. Weeds had a significant negative effect on corn yields; the possible beneficial effects of such vegetation on enhancement of carabid activity density should be compared to the potential negative effect of corn yield loss. These results suggest carabid species respond differently to vegetational diversity, perhaps due to a number of factors, including suitable prey availability and microclimate preferences.

Effects of woodland shape on the spatial distribution and density of 17-year periodical cicadas (Homoptera: Cicadidae)

Abstract: -We tested the hypothesis that the shape of woodland fragments influences the spatial distribution and density of three species of 17-year periodical cicadas (Homoptera: Cicadidae: Magicicada spp.). These characteristics were quantified for periodical cicadas emerging in four rectangular woodlots (mean size = 3.4 ? 0.7 ha), four linear wooded fencerows (>400 m long by mean width = 15.9 + 3.9 m), and the last remaining stand (81 ha) of primary beech-maple forest in southwestern Ohio, during the emergence of Brood X, May-June 1987. The shape of woodland fragments influenced spatial distribution and density of cicadas, although other factors, particularly the disturbance history of the sites, were equally important. Emergence began earlier in linear wooded fencerows and rectangular woodlot edges than in the interior of woodlots. Density of emerging individuals was greatest in the least disturbed edge areas and was low within the interior of rectangular woodlots. The relative abundances of the cicada species differed significantly between the woodland fragments and the primary forest. The smaller species, M. cassini (Fisher) and M. septendecula (Alexander and Moore), constituted over 93% of all individuals in all the linear and rectangular forest fragments, but the larger species, M. septendecim (L.), constituted 68% of individuals in the interior of the primary forest. We concluded that woodland shape influenced the spatial distribution of cicadas within the fragments, mainly due to the concentration of cicadas in edge areas. Our data also indicated that forest fragmentation shifted the relative abundances of these cicada species to the detriment of M. septendecim.

Long-term changes in parasite population and community structure : a case history

Abstract: -A series of studies on the population and community ecology of several digenetic trematodes was begun in 1983 in a small, eutrophic impoundment in the Piedmont area of North Carolina. Initially, efforts were focused on the hemiurid trematode, Halipegus occidualis. Prevalence of this parasite in its snail intermediate host, Helisoma anceps, reached 60% in late June-early July, then dropped precipitously as the mature cohort of the snail host died-off. Over the next 13 yr, this annual pattern consistently repeated itself. Several years later, another pulmonate snail, Physa gyrina, colonized the pond. Either simultaneously, or closely thereafter, Halipegus eccentricus and two other species using P gyrina as an intermediate host also appeared. The trematode infracommunities in both hosts were examined; structuring forces were found not to be affected by competitive interactions among larval trematodes, but by a variety of factors, including snail vagility and size (age), microhabitat heterogeneity, distribution and temporal visitation patterns of definitive hosts, and the sequence of parasite recruitment mechanisms. Very few ( 7000 Helisoma anceps, whereas nearly 19% of all infections in 1181 P gyrina were multiple. Additional studies indicate that Halipegus occidualis cercariocysts do not remain infective for extended periods for second intermediate hosts (ostracods) as suggested in the older literature. Moreover, foraging ecology by odonate naiads is a significant factor in the recruitment and dispersion patterns of H. occidualis metacercariae. The long-term population ecology of H. occidualis and H. eccentricus was examined in mark-release-recapture studies of Rana clamitans, the definitive host. Halipegus occidualis prevalence and density were higher than those of H. eccentricus, although both were contagiously distributed in their frog definitive hosts. Halipegus occidualis exhibited large and rapid changes in density within frog hosts. Increases were probably because of the recruitment of contagiously distributed parasites from their third intermediate host, whereas declines in heavily infected definitive hosts were attributed to inflammation and tissue sloughing at the point of parasite attach-

Leaf Domatia and the Distribution and Abundance of Foliar Mites in Broadleaf Deciduous Forest in Wisconsin

Abstract: -Leaf domatia occur frequently in vein axils on the leaf undersurface of many woody Dicotyledonae in the broadleaf deciduous forests of the northern hemisphere. These structures are often used by mites for shelter and as sites for egg laying. Taxa of predatory and fungivorous mites and sometimes of herbivorous mites were associated with the domatia of six species of trees or woody vines (Quercus velutina, Q. rubra, Acer saccharum, Prunus virginiana, P serotina and Vitis riparia) examined near LaValle in S-central Wisconsin. Comparisons of mite frequency and abundance in different leaf microhabitats (in domatia, in major vein axils without domatia, along the midrib, and on the leaf lamina) showed that mites respond strongly to leaf architectural features, especially domatia. Further, mite evidence was more frequent or mites more abundant on leaves of species with domatia in four of five paired-species comparisons. The abundance of potentially beneficial mites, primarily Metapronematus leucohippeus (Tydeidae) and Typhlodromus nr. pomi (Phytoseiidae) was significantly greater and the overall ratio of beneficial to herbivorous mites was greater on leaves of species with domatia. Leaf domatia are important shelters for potential plant mutualists and alter the distribution and abundance of foliar mites in the canopy of temperate broadleaf

Shell strength of mud snails (ilyanassa obsoleta) may deter foraging by diamondback terrapins (malaclemys terrapin)

Abstract: Diamondback terrapins (Malaclemys terrapin) do not eat the common and abundant mud snail (Ilyanassa obsoleta) even though terrapin diets are dominated by similarly sized gastropods. To resolve this paradox, we tested a structural defense hypothesis as the potential deterrent against predation. We compared resistance to compressive force of Ilyanassa and three invertebrates (Littorina irrorata,) Uca spp, and Callinectes sapidus) that terrapins commonly eat. Ilyanassa shells were 2-3 times more resistant to crushing than the other prey. High processing costs for mud snails (in terms of structural resistance to crushing) may deter predation by terrapins despite the low search costs and equivalent energetic returns relative to alternative prey items.

Effects of Radio Tags on Captive Northern Bobwhite (Colinus Virginianus) Body Composition and Survival

Abstract: -We conducted a pen study to determine the effects of radio tags on northern bobwhite (Colinus virginianus) body composition and survival. Two groups of 50 birds were fitted with radio tags using two attachment styles (backpack or bib); a third group of 50 birds with no radio tags served as controls. During 12 wk, we monitored weekly live body mass and lipid mass and noted whether tags were attached properly. After 12 wk, the birds were sacrificed and total body lipids, lean mass and water mass were determined. Body and lipid mass did not vary among groups before we attached tags. After 12 wk, tagged birds had significantly lower body weights and less lipid mass than controls. Birds with bibs had significantly lower survival rates than birds with backpacks. Most of the tagged birds (54%) experienced problems with their harnesses. Neither harness design was clearly superior because both designs had a high incidence of problems. Loss of lipids can reduce survival by reducing energy reserves and lower nesting success by reducing clutch size or delaying onset of ovulation. Harness problems may increase vulnerability of tagged birds to predation. Thus, estimates of survival and nesting effort obtained with radio-tagged quail may be biased. Alternative attachment designs should be evaluated, and alternatives to radio tags that are less stressful to the birds (e.g., whistle counts) should be favored when possible.

Scale-dependent habitat selection by the darkling beetle eleodes hispilabris (coleoptera : tenebrionidae)

Abstract: -Habitat selection in the darkling beetle Eleodes hispilabris Say (Coleoptera: Tenebrionidae) on the shortgrass prairie of the central United States was nonrandom at both a broad (km2) and a fine (cm2) scale, relative to the abundance of broadly defined habitat types and, within these, microhabitats. On a broad habitat scale, darkling beetles were more numerous and had longer residence times (as assessed by recapture rates) in shrub floodplains than in shortgrass uplands. On a microhabitat scale, beetles used patches of vegetative detritus more and bare ground areas less than expected, based upon the availability of these microhabitats. Broad-scale patterns of habitat selection may reflect microhabitat preferences, as shrub floodplains possessed relatively more vegetative detritus (a darkling beetle food source) than did shortgrass uplands. Such an ability to explain how a phenomenon at one scale affects a pattern at another scale will allow for patterns of habitat selection across multiple scales to be predicted.

Species composition in a central hardwood forest in Kentucky 11 years after clear-cutting

Abstract: -Forest regeneration was examined 5 and 11 yr after a clear-cut in a central hardwood forest in eastern Kentucky. Prior evidence suggested that regeneration following clear-cutting in the central hardwood forest region was dominated by stump sprouts, resulting in rapid regeneration of stands which closely resemble the original forest in species composition. Five yr after clear-cut, stump sprouts accounted for 50% of all stems, and remained unchanged 11 yr after clear-cut. During the same 6 yr, relative density of root sprouts increased from 17 to 42% and seedlings decreased from 34 to 8% of all stems. These changes in relative density likely reflect competitive advantages of sprouts over seedlings as well as competition among sprouts on the same root. Despite low numbers, seedlings are an important source of regeneration for some species. Regeneration of overstory species increased in importance relative to understory species during the 6-yr interval between samples. This shift results from higher net loss among stump sprouts of understory than overstory species, and resulted in species composition similar to that of the predisturbance forest except for a much larger component of red maple (Acer rubrum) and lower component of hickories