Showing papers in "American Midland Naturalist in 1996"

Bird abundance and nesting success in Iowa CRP fields: the importance of vegetation structure and composition.

Abstract: -Bird use of Conservation Reserve Program (CRP) and row-crop fields was studied in central Iowa from May through July 1991-1993. Thirty-three bird species were recorded in CRP fields and 34 in row-crop fields. The most abundant species in both habitats was the red-winged blackbird (Agelaius phoeniceus), accounting for 35% of all birds in CRP and 24% in row-crop fields. The dickcissel (Spiza americana), grasshopper sparrow (Ammodramus savannarum), bobolink (Dolichonyx oryzivorus), common yellowthroat (Geothypis trichas), brown-headed cowbird (Molothrus ater), savannah sparrow (Passerculus sandwichensis) and ring-necked pheasant (Phasianus colchicus) were the next most abundant species in CRP plots. The horned lark (Eremophila alpestris), vesper sparrow (Pooecetes gramineus) and brownheaded cowbird were the next most abundant species in row-crop fields. Nests of 16 bird species were found in CRP fields, with red-winged blackbirds accounting for 48% of all nests found. The vesper sparrow and horned lark were the only species nesting in row-crop fields. The major cause of nest loss for all species was predation, accounting for 52% of all nest loss in CRP fields and 65% in row-crop fields. Mammals accounted for 89, 88 and 85% of the predation on grasshopper sparrow, red-winged blackbird and dickcissel nests, respectively. The Conservation Reserve Program has likely contributed to an increase in the abundance of many bird species in central Iowa, inasmuch as the row-crop habitat that it replaced has lower bird abundance and supports fewer nesting species. The vegetation structure and composition of CRP fields in central Iowa are diverse, resulting in differences in the bird species communities using these fields. The effects of several land-management practices are discussed relative to bird species composition and nesting success.

Impact of Fire on Small Mammals and Amphibians in a Central Appalachian Deciduous Forest

Abstract: -The impact of fire on small mammals and amphibians was investigated in an oak (Quercus spp.)-dominated forest in S-central Pennsylvania. Sampling with Y-shaped arrays of pitfalls and drift fences was conducted for 78 days between 31 March and 13 November 1992 following a fire in November 1991. Shrews, rodents and total small mammals were significantly less abundant in burned than in unburned forest; however, significant differences between habitats were recorded only for the 1st 3 sampling periods (April, June, July) for rodents and total small mammals. Eight species of small mammals were captured in unburned forest compared to six species in burned areas. The two species not taken in the burned forest were both arvicoline rodents, the meadow vole (Microtus pennsylvanicus) and southern red-backed vole (Clethrionomys gapper). A significant correlation was found between the rank order of species of small mammals taken in burned and unburned habitats. The two most abundant species in both habitats were the white-footed mouse (Peromyscus leucopus) and Maryland shrew (Sorex fontinalis), which combined comprised 78.1% of the small mammals taken in the unburned forest and 72.4% of the sample from the burned site. In contrast to small mammals, significantly more amphibians were captured in the burned forest. The American toad (Bufo americanus) was the most abundant amphibian, comprising 70.8% of the amphibians captured; this species was largely responsible for the greater numbers of amphibians captured in the burned forest.

Recent fire history of the northern great plains

Abstract: -The fire history of the northern Great Plains has been largely reconstructed from the historical record. To clarify this history, segments of 1-m cores from four lakes in North and South Dakota and northeastern Montana were examined for charcoal fragments. The cores spanned a time interval of 172 to 380 yr. Samples integrating 5-10 yr of deposition were taken from 2-cm sections along each core and sieved. Charcoal concentrations ranged from 6-14,799 fragments/gram of sediment, and mean charcoal abundance was negatively correlated with longitude. Results suggest periods of increased fire from A.D. 1700-1740 and A.D. 1850-1900. These peaks were broadly synchronous across the region and ranged in duration from 20-40 yr. Postsettlement patterns of charcoal deposition were highly variable but generally much lower than presettlement intervals.

Bobcat (lynx rufus) home range size and habitat use in northwest wisconsin

Abstract: Bobcats were radio-tagged and monitored to estimate and compare annual and seasonal patterns in home range size and habitat use in northwestern Wisconsin. Annual and seasonal male home ranges extensively overlapped those of other males and females, whereas females maintained more exclusive areas. Annual male home ranges (60.4 km2 ? 23.4 kM2) were 112% larger than those of females (28.5 km2 + 3.7 kM2). Females expanded and contracted their home ranges seasonally; the largest home ranges occurred in winter. Males shifted similar-sized ranges seasonally resulting in larger annual ranges. Male bobcats selected lowland conifer forests, and avoided upland conifer stands, upland deciduous forest and mixed savanna cover-types. Females exhibited similar preferences but also selected for lowland deciduous forests and avoided unforested areas. Seasonal shifts in habitat use were evident for males and females; both used lowland conifer stands more, and unforested areas and upland deciduous forests less, in winter. The selection of lowland coniferous forests by males and females during all seasons suggest these areas are important range components

Factors Influencing Burrowing Owl (Speotyto cunicularia) Nest Densities and Numbers in Western Nebraska

Abstract: -Burrowing owls (Speotyto cunicularia) were studied at 21 prairie dog towns in native prairie and 17 native prairie pastures with badger (Taxidea taxus) burrows in the Nebraska panhandle in the spring and summer from 1989-1991. The number of nesting burrowing owl pairs ranged from 1-20 in prairie dog (Cynomys ludovicianus) towns and from 1-4 in pastures with badger burrows. Burrowing owl densities in small prairie dog towns ( 35 ha) prairie dog towns ranged from 0.9-2.5 owls/ha. Mean nearest-neighbor distance (?SE) in clusters within large (?35 ha) prairie dog towns was 125.0 m + 4.6, whereas the mean distance between owl nests in small towns (<35 ha), where owls did not have the space to cluster, was 105.1 m + 7.4. Mean nearest-neighbor distance for owls nesting in pastures with badger burrows was 240.2 m ? 39.2. No relationship was found between owl numbers and number of active or inactive prairie dog burrows. In 1990 burrowing owl density was inversely related to active burrow density, but no relationship was found in 1991. Burrow availability may be a limiting factor for owls nesting in pastures with badger burrows. As the size (ha) of prairie dog towns increased, burrowing owls occurred in higher numbers but lower densities.

Fire impact on groundlayer flora in a sand forest 1990-1994.

Abstract: -Groundlayer response to prescribed fire was monitored in a central Illinois sand forest between 1990 and 1994. The first of three annual fires resulted in a significant increase in richness and cover of herbaceous species, and a minor decrease in woody cover. Successive fires maintained or slightly increased herb richness and cover, but did not change woody cover. Before burning, the forest understory was dominated by dense shrubs (7489% cover) over a sparse herb layer (4-18% cover). After the first fire, herb cover increased over fourfold to 48-57%, and to 65-66% after the second fire. Fire nonsignificantly reduced woody cover by some 20%, primarily due to a reduction in Parthenocissus quinquefolia (Virginia creeper), but did not affect frequency of woody vegetation. Species richness increased over 50% after the first fire, from 6.2-7.0/M2 to 9.8-10.8/M2, due to the increased frequency of herbaceous, and especially annual, species. Most of the postfire increase in herbaceous cover was due to Eupatorium rugosum (white snakeroot), which increased from 3X higher than preburn levels. The alien biennial Alliaria petiolata was maintained in a reduced condition by repeated fires, but in the absence of fire doubled in cover every 2 yr, from 4.6% in 1990 to 8.6% in 1992 to 17.0% in 1994.

Are road kills valid indicators of armadillo population structure

Abstract: -We collected 3 yr of data on road-killed nine-banded armadillos (Dasypus novemcinctus) to determine if these individuals were representative of the population as a whole. Comparisons between road kills and an adjacent live-caught population revealed no differences in sex ratios or the reproductive condition of adult females. However, there was a significant difference in the age structure of the two groups, with almost no juvenile road kills. Our live-caught population appeared representative of armadillo populations in general. Comparisons of the demography of this population with that from two other live-caught groups revealed no significant differences. Our data suggest that road-killed armadillos provide a representative picture of the demography of the adults in a population, but that information on age structure is misleading.

Effects of microtopography and disturbance on fine-root dynamics in wetland forests of low-order stream floodplains.

Abstract: -Fine-root mass and net primary productivity (NPP) were assessed in two forested wedlands located in floodplains of low-order streams in southern Alabama. In one experiment, live and dead fine-root (<5 mm diam) mass in the upper 20 cm of soil were estimated by periodic soil coring for 7 mo. Cores were collected from P-fertilized and unfertilized portions of three microsite types: hummock, flat and hollow. In a second experiment, cores to 50 cm deep were collected from clear-cut and adjacent unharvested (reference) zones for 19 mo. In the first experiment, fine-root mass was significandly affected by microsite but not fertilizer. Roots were least abundant but temporally most variable in hollows, and fine-root NPP (estimated by summing root mass differences between sample dates) was greatest in hollows followed by flats and hummocks. In the clear-cut experiment, total fine-root mass was highly variable in clear-cut and reference sites. The ratio of liveto totalroot mass was significandly lower on clear-cut sites on four of nine sample dates. NPP in the upper 50 cm of soil ranged between 1.90 and 4.55 megagrams per ha per year and was consistendly, but not significantly, greater on reference than on clear-cut sites. This study suggests that fine-root dynamics in forested wetlands are affected by microtopography and possibly by disturbance to the overstory.

Reproductive Success of Grassland Birds at East- Central Illinois Airports

Abstract: -We determined the densities and reproductive success of birds on seven airport grasslands in east-central Illinois between 10 April and 15 August 1994. One hundred and forty-seven nests of six species were found. Eastern meadowlark (Sturnella magna) was the most abundant nesting species (71% of 147 nests). Other nesting species included: grasshopper sparrow (Ammodramus savannarum), savannah sparrow (Passerculus sandwichensis), red-winged blackbird (Agelaius phoeniceus), song sparrow (Melospiza melodia) and horned lark (Eremophilia alpestris). Overall nest success was 14%, and nest success at individual airports ranged from 0.02% to 29%. Most known nest failure was attributed to mowing (44% of all nests). Thus airport grasslands appear to be population sinks for most grassland birds. Although the overall nest density was only 0.79 nests/ha; eastern meadowlark nest density was 0.56 nests/ha. This is a relatively high value compared to other studies. The relatively high nest densities and low nest success suggest that airport grasslands may be ecological traps for eastern meadowlarks and may be contributing to regional declines of other grassland species.

A comparison of presettlement and present-day forests in two northern michigan deer yards

Abstract: Deer yards are wintering areas used by white-tailed deer in the northern part of their range. In northern Michigan, deer yards typically consist of extensive stands of cedar- dominated (Thuja occidentalis) or mixed conifer swamps where thick evergreen overstories provide shelter from winter conditions. Forest and wildlife management in and around cedar- dominated swamps of the upper Great Lakes have created a nearly optimal interspersion of early-seral summer range and mature conifer winter range. For a variety of reasons which include favorable habitat changes, deer populations are today larger than those of presettle- ment conditions. We used General Land Office survey records from the 1840s to compare presettlement forest composition with present-day forest composition in two important deer yarding areas in Michigan's Upper Peninsula. Except for tamarack (Larix laricina), woody plant species that are unpalatable to deer or tolerant of browsing have increased. Species that are palatable and intolerant of browsing have decreased. Ages of extant mature cedars indicate establishment during a period of low deer populations in Michigan. Change in forest composition has many causes, but deer populations encouraged by forest and wildlife man- agement may contribute to a changing ecology in northern Michigan's conifer swamp com- munities, and may change the structure of plant communities in areas where deer use is concentrated.

Movements and habitat use of subadult alligator snapping turtles (macroclemys temminckii) in louisiana

Abstract: -We conducted a telemetry study of subadult alligator snapping turtles (Macroclemys temminckiz) to investigate movement and habitat use. Available habitat consisted of baldcypress forest (Taxodium distichum) (69.1%) and open channel (30.9%). Twelve (three male, nine female) turtles from Bayou Desiard in northeast Louisiana were each equipped with an ATS external radio transmitter and returned to the capture location within 2 h. A total of 1327 location fixes were recorded from March 1992 toJune 1993. At each fix location the date, time, water temperature and depth, direction from last fix and capture site, and nearest shoreline, and habitat were recorded. Significant differences were noted between male and female mean fix distance (males = 352.2 m, females = 160.3 m), mean percentage of movement fixes (males = 62.7%, females = 42.7%) and mean home range length (males = 3495.1 m, females = 1423.2 m). The percentage of movement fixes and fix distance was highly correlated with water temperature but not with the size of the turtle. Turtles preferred the baldcypress forest to open channel. Males and females had significant differences in microhabitat use; 56.1% of male fixes were associated with structures (e.g., logs) compared to 79.7% for females. Turtles returned to specific microsites and there were no overland movements. Subadult and adult alligator snapping turtles in Bayou Desiard have similar movement patterns and habitat use.

An anther-smut disease (Ustilago violacea) of fire-pink (Silene virginica): its biology and relationship to the anther-smut disease of white campion (Silene alba).

Abstract: -In the southeastern United States, anther-smut disease (Ustilago violacea) was observed on the native fire pink (Silene virginica), and on the introduced white campion (Silene alba). Fungal isolates from the two host species showed fixed differences at allozyme loci, and isolates from S. alba were similar to isolates from S. alba in Europe. Fungal isolates from S. virginica did not produce disease on S. alba; crosses between fungal isolates from the two hosts showed reduced inoculation success on S. alba. Teliospores from hybrids between the isolates showed abnormal sporidial development. We conclude that the two anthersmuts from each of the host species are genetically distinct and partially reproductively isolated "host-races." Ustilago violacea occurs on S. virginica throughout its range, and far beyond the range of diseased S. alba. Rates of infection of healthy flowering individuals in natural populations of S. virginica were very low, but a large fraction of plants were already diseased when they first flowered, suggesting disease is transmitted by spores that fall on seedlings or rosettes. There was substantial heterogeneity in disease incidence even among local populations in the same vicinity, but evidence suggests that the disease was not rapidly spreading in S. virginica.

Intraspecific competition in the goldenrod ball-gallmaker (Eurosta solidaginis): larval mortality, adult fitness, ovipositional and host-plant response

Abstract: Intraspecific competition can be an important factor affecting population structure for herbivorous insects. Here we investigate whether high larval density has detri- mental effects for the goldenrod ball-gallmaker, Eurosta solidaginis (Diptera: Tephritidae). First, in a field study of E. solidaginis populations attacking the host-plant, Solidago altissima (Compositae) we found high numbers of ovipunctures per bud which suggested that high mortality could result from intraspecific larval competition. Second, a greenhouse experi- ment was performed to determine if larval mortality increases with numbers of larvae present in a bud of the host plant and to determine subsequent effects on emergence and fitness. Replicates of a single susceptible host-plant genotype were randomly assigned to either low or high ovipuncture-attack treatment groups. The number of eggs oviposited increased sig- nificantly with the number of ovipunctures per bud. However, by 3 wk after oviposition, there was no significant difference in the number of larvae between the two treatments. Larval mortality during this pregall stage resulted from direct larval interference, tissue necrosis (a plant resistance mechanism induced by high levels of infestation) and buds damaged by excessive ovipuncture. In multiple-galled ramets, emergence of adults from upper gall posi- tions was significantly reduced compared to the bottom gall positions, suggesting depletion of some limiting resource. Adult longevity increased significantly with adult mass, whereas longevity of adults decreased for flies that emerged from multiple-galled ramets compared to single-galled ramets. Consequently, fecundity could be affected by larval competition. Ovi- positing females decreased the rate of egg deposition at high levels of ovipuncture suggesting that buds already containing a high number of ovipunctures are less acceptable for .egg deposition. Where acceptable hosts are not easily found, females may oviposit into less pre- ferred genotypes or shift to closely related but novel host species.

Recruitment and Establishment of Salt Marsh Plants Following Disturbance by Flooding

Abstract: -Several winter rainstorms that occurred between 1982 and 1986 deposited a large amount of virgin sediment, covering approximately 0.25 ha at the mouth of Pine Gulch Creek in a coastal salt marsh in Bolinas Lagoon, Marin County, California. The establishment of a new marsh community was followed at this site from 1987 to 1991. Seedling survival was relatively low with only 5% surviving for a year or longer. Seedlings which did become successfully established rapidly by expanded vegetative growth. Salicornia virginica, Frankenia grandifolia and Distichlis spicata were the most successful species occupying at least 20% cover across most of the study area, but other species became established as well. Seedling survival and plant establishment were greatest in 1989 following heavy spring rains which provided large inputs of freshwater. Disturbances followed by conditions that lower stress, which would otherwise prevent germination and growth, are important for the rapid establishment of a marsh at Bolinas.

Effects of nutrient level on cost and benefit of apical dominance in Epilobium ciliatum.

Abstract: -The disruption of apical dominance has been considered fundamental to the overcompensatory response to herbivory in many plant species. For isolated plants, such overcompensation can be interpreted as a cost of apical dominance since the growth of apically intact plants is limited by the number of active meristems. When apical dominance is disrupted, growth becomes limited more by nutrient levels and so the greatest overcompensation is generally predicted for plants grown under high nutrient levels. This relationship, although possible for plants growing free from competition, may not hold true when plants are competing for light. In competing plants, the retention of apical dominance, expressed through a strong vertical component of growth, represents a benefit, as plants may outcompete those from which apical dominance is removed. In this case, undercompensation rather than overcompensation may be expected following shoot apex removal under high nutrient levels, since high nutrient levels generally promote competition for light. We tested these predictions concerning cost and benefit of apical dominance in Epilobium ciliatum. Fitness estimates (i.e., dried biomass, capsule weight and number) were compared between apically decapitated and intact plants grown in the presence and absence of neighbors and under three different nutrient levels. Cost of apical dominance (overcompensated capsule production following shoot apex removal in the absence of neighbors) was detected only under the intermediate nutrient level, not the highest nutrient level as generally predicted. This was interpreted by recognizing that increases in nutrient level may decrease the strength of apical dominance. Thus, under high nutrient levels, architectural modifications, and thus the potential fitness benefits following the disruption of apical dominance, may be minimal. This leads to the general prediction that overcompensation (cost of apical dominance) should be most common in habitats of intermediate fertility. Benefit of apical dominance in E. ciliatum (in terms of capsule production) was most evident for competing plants grown under high nutrient levels where competition for light is expected to be most intense.

Sex-biased response of raccoons (procyon lotor) to live traps

Abstract: -Heterogeneity of response to traps has important implications when interpreting mark-recapture data. We used radiotelemetry to investigate variations in recapture probability for adult raccoons (Procyon lotor) during live trapping conducted in S Texas from 1990-1992. Both sexes had higher recapture rates in winter/spring trapping periods than summer/autumn (males P < 0.001, females P < 0.001). Adult males were consistently captured more frequently than adult females in all trapping periods. There was a higher proportion of 'available' males captured while some females avoided capture. In addition to differences in movement patterns, intersexual behavioral differences in response to live traps were suggested.

The influence of prairie and forest vegetation on soil moisture and available nitrogen

Abstract: -Aspen clones have expanded into prairie during the last century at the northern edge of the Great Plains. Soil under aspen has more water and available N than that under adjacent prairie. We used a field experiment to test whether high resource availability in forest soil was attributable to the environment associated with forest vegetation. We collected 80 soil cores from prairie and forest and moved them to either prairie or forest. Neighboring roots were excluded from half the cores. Cores were moved in April and 10 samples were taken from each core in September. Cores from forest had significantly higher moisture and available N than those from prairie. Cores moved from forest to prairie had significantly less moisture than those moved from forest to forest, suggesting that the lower moisture in prairie soils depended partly on the environment associated with prairie vegetation. Available N did not differ between cores moved to prairie and forest. Both water and N were higher in cores with roots excluded, but the magnitude of this difference did not differ between prairie and forest, suggesting that there were no differences between prairie and forest in their abilities to take up these resources. The spatial variability of soil moisture was significantly higher in cores from forest than in those from prairie and tended to be highest in cores with roots present, which was consistent with the idea that uptake enhances resource heterogeneity.

Feeding ecology of Merriam's turkeys ( Meleagris gallopavo merriami ) in the Black Hills, South Dakota

Abstract: W e studied the feeding ecology of Merriam’s turkey (Meleagris gallopavo merriami) in the Black Hills, South Dakota, between 1986 and 1989 Adult birds consumed 78 kinds of food, of which four food categories constituted >79% of winter diets and six food categories constituted >75% of summer diets Ponderosa pine (Pinus ponderosa) seeds were the preferred winter food and birds selected habitats where pine seed abundance was highest During drought, ponderosa pine produced fewer seeds and winter turkey diets were predominantly kinnikinnick (Arctostaphylos uva-ursi) fruits and herbaceous foliage and seeds Merriam’s turkeys consumed more green foliage from late winter through spring Summer diets were mostly grass seeds and foliage Arthropods comprised >60% of the poult diets Poults 13 wk old consumed more arthropods than poults >7 wk old Grasshoppers (Orthoptera) and beetles (Coleoptera) were the primary arthropods eaten by poults Brood hens selected macrohabitats where arthropod abundance was highest Poults selected arthropods with large mass/individual and disregarded some arthropods that were abundant but with low mass/individual

Helminths and food habits of lake sturgeon acipenser fulvescens from the lake winnebago system, wisconsin

Abstract: -Eight species of helminths were recovered from 45 summer (June-August) and 29 winter (February) lake sturgeon adults and juveniles, from Lake Winnebago, Wisconsin. Eighteen young-of-the-year (YOY) sturgeon collected from the Wolf River were uninfected. Both summer and winter helminth communities were dominated by host specific parasites such as Crepidostomum auriculatum, Skrjabinopsolus manteri, Capillospirura pseudoargumentosa and Truttaedacnitis clitellarius. Examination of stomach contents indicated that chironomids were the most important food items and comparison with past records on lake sturgeon diet suggests an unchanged use of the benthos of Lake Winnebago. The eutrophic nature of Lake Winnebago is probably responsible for the absence of Hexagenia spp., an important component of the diet of lake sturgeon from other systems, which would explain the absence of a host specific nematode, Spinitectus acipenseri. Although the trophic status of the lake may modify the helminth community, some host specific endo-helminths (C. auriculatum, C. pseudoargumentosa) appear to be transmitted in riverine environments (deeper downstream channels) used as feeding areas by older (2 yr+) sturgeon. Differences in habitat and diet of YOY sturgeon in the Wolf River and the absence of any host specific helminths in these juveniles also indicate that the community of host specific helminths is not recruited until YOYjuveniles enter deeper downstream channels to feed.

Historical changes in a herpetofaunal assemblage in the flint hills of kansas

Abstract: -To assess changes in the herpetofauna in the northern Flint Hills of Kansas, we conducted a survey on the Fort Riley Military Reservation (Riley and Geary counties) in 1993 and compared our results with those of C. E. Burt and other early collectors. Of 46 species reported before 1930, 37 were found in 1993. Four species recorded before 1930 and not found in 1993 (Bufo cognatus, Carphophis vermis, Thamnophis radix and Crotalus horridus) are known or believed to persist in Riley and Geary counties. Four other species (Heterodon platirhinos, Nerodia erythrogaster; N. rhombifer and Regina grahamii) have not been reported in over 50 yr and may be extirpated locally. Two additional species (Spea bombifrons and Trachemys scripta) found in 1993 were not reported by early collectors. Changes in relative abundance of species from pre-1930 to 1993 were few, and there was no evidence of decline in amphibian populations. With the exception of declines in species dependent on rare habitats located in the floodplain of major rivers, the herpetological assemblage in the Fort Riley area has changed little during the past 70-100 yr. We attribute this stability to land uses that have maintained large tracts of native vegetation.

Epizoic Invertebrate Communities on Upper Mississippi River Unionid Bivalves

Abstract: -Based on the Great Lakes experience with Dreissena polymorpha, it is clear that the native freshwater mussel (family Unionidae) fauna will be one of the riverine communities most severely impacted if high zebra mussel densities occur. Negative impacts on unionids will also affect the epizoic invertebrate communities that live on the shells of the unionids. In 1991 and 1992 (prezebra mussel infestation) we determined the composition and density of epizoic invertebrates on individual unionids from the upper Mississippi River. The 1991 samples were from a location with a strong current; the numerically dominant epizoic invertebrates at this location were three species of hydropsychid caddisflies and the chironomid larvae: Polypedilum convictum, P scalaenum group, Rheotanytarsus sp., Microtendipes pedellus group and Thienemannimyia group. Strong correlations existed between effective surface area (ESA) (amount of shell surface area above the sediment-water interface) of the individual unionids and: (1) number of epizoic chironomid larvae (r = 0.81); (2) number of hydropsychid caddisflies (r = 0.73), and (3) total number of epizoic invertebrates (r 0.78). Sampling in a slower current area in 1992 revealed an epizoic composition dissimilar from that observed in 1991. Glyptotendipes nr. lobiferus was the most abundant epizoic larval chironomid, and, although caddisfly larvae were common, they mostly belonged to families other than the Hydropsychidae. Again, strong correlations existed between ESA of the unionids and: (1) total number of epizoic invertebrates (r = 0.64) and (2) number of epizoic chironomid larvae (r = 0.57). A strong correlation also existed between the size of the unionids and the number of epizoic taxa present (1991: r = 0.78; 1992: r = 0.77). Fiftythree invertebrate taxa were collected from the unionids; mean epizoic densities were ca. 9600 and 6400 invertebrates/M2 of ESA in 1991 and 1992, respectively. These results indicate that unionids are important substrates for epibenthic invertebrates, especially in rivers in which other large clean substrates are in short supply.

Life History and Population Characteristics of the Salamander Plethodon kentucki with a Review of Plethodon Life Histories

Abstract: To determine life history and population characteristics of the Cumberland Plateau woodland salamander (Plethodon kentucki), I conducted a three-yr mark-recapture study on two 225-M2 plots in southeastern Kentucky. I also observed egg clutches deposited by three captive females in the field and laboratory. Individual females reproduced biennially or less frequently; males bred annually. Mean clutch size was 10, and eggs were deposited in July and hatched during October. Hatchlings were 14 to 15 mm snout-vent length (SVL), and average growth was ca. 15, 10 and 6 mm SVL during the 1st, 2nd and 3rd yr of life aboveground. Thereafter growth continued to decline steadily with increasing body size. Growth rate of 2-yr-old juveniles varied significantly among years. Males reached sexual ma- turity at ca. 48 mm SVL (3-4 yr after hatching). Females began depositing eggs at about 52 mm SVL (probably 4-5 yr after hatching). Mean SVL for adult females (56.6 mm) was significantly greater than for adult males (54.1 mm). Jolly-Seber estimates of annual adult survival rate ranged from 0.72 to 0.91. Recapture rates among years showed that 2- and 3-yr- old juveniles had an annual survival rate of at least 0.48 and 0.68, respectively. Some micro- habitats supported significantly higher population densities than others, and densities varied little from year to year. Overall adult sex ratios were around 1:1 or significantly biased toward females, whereas the ratio of males to gravid females was significantly biased toward males in some years. Variation in life history and population characteristics between localities and years demonstrates the necessity of long-term studies on different populations when describ- ing salamander life histories.

Fine-root biomass distribution and production along a barrier island chronosequence

Abstract: -Fine roots are important in community development on barrier islands. Fine roots can influence nutrient losses from the soil environment along with regulating water loss based on their distribution and concentration. A sequential coring method was used to determine live fine-root biomass along a barrier island dune and swale chronosequence on the Virginia Coast Reserve-Long Term Ecological Research Site. Fine-root production and the effects of nitrogen fertilization were also examined using an in-growth core method along the chronosequence. Variation in biomass was associated with topographic position and the interaction with nitrogen and water availability along the chronosequence. The swales had significantly larger accumulations (16 to 180 g/m2) of live fine-root biomass (LFRB) than the dunes (4 to 13 g/m2). Higher LFRB was probably due to higher nitrogen levels and moister conditions in the swales. LFRB changed very little across the dune chronosequence but LFRB in the swales generally decreased from the 6-yr to the 120-yr site. However, the 6yr swale had significantly lower biomass than the other swales. LFRB was concentrated in the upper 10-20 cm of soil in dune and swale sites across the chronosequence, with swales having proportionally more (70%) in the upper 10 cm of soil than dunes (29%). Root nitrogen concentration in LFRB was higher in the older dunes and swales. Root phosphorus concentrations increased from the 6-yr to the 120-yr dune but were not different in the swales. Fineroot production increased significantly with N-fertilization in the dune communities, 1.5 times to 2.5 times the reference sites. Nitrogen fertilization also increased nitrogen concentrations in live fine roots.

Effects of a thermal effluent on macroinvertebrates in a central Texas reservoir

Abstract: We investigated the impact of a thermal effluent from an electricity-generating plant on the macroarthropod community in a central Texas reservoir for 1 yr by comparing the community of a 60-ha pond directly receiving the effluent to an area in the main body of the reservoir relatively unaffected by the effluent. Temperature of the pond averaged 7.2 C warmer than the main reservoir sites. Samples of artificial substrates constructed to mimic macrophytic vegetation indicated that the pond generally had lower macroinvertebrate abundance and reduced taxonomic diversity, though direction and severity of effects varied over time for most taxa. Deleterious effects were most severe in summer when temperatures of 40-42 C in the pond eliminated macroinvertebrates. Although taxa recolonized the pond after the summer defaunation, with some taxa briefly obtaining very high population levels, most taxa maintained lower population levels in the pond than the main reservoir throughout the winter. 32 refs., 3 figs., 1 tab.