The objective of this study was to establish baseline data for the structure and dynamics of an old-growth beech (Fagus grandifolia)-sugar maple (Acer saccharum) woods in northeastern Ohio before the anticipated future impacts of disturbances such as beech bark disease. Several parameters were selected for study based on their likelihood of being influenced by these disturbances including: (1) species composition; (2) mortality and growth rates of trees, overall, by species and by size class; (3) canopy replacement patterns; (4) coarse woody debris (CWD) characteristics; and (5) the understory response to existing openings and its implications for change in the forest under present conditions. This study extends our understanding of beech-sugar maple old growth because our site is, perhaps, the most northeasterly one not yet affected by beech bark disease and because it is the only studied site influenced by weather conditions generated by Lake Erie.

The overall annual mortality rate (from 1992 to 1997) of 2.3% was higher than that reported for other old-growth woods (1%). Mortality was highest for the large canopy stems (≥50 cm dbh) of beech and the subcanopy stems (10–25 cm dbh) of sugar maple. Growth rates decreased with stem size for beech, but increased with stem size for sugar maple. Over the 5 y period beech decreased in relative basal area and relative density whereas sugar maple increased in both measures. CWD mass (35.9 Mg ha⁻¹) was similar to other old-growth deciduous forests. Beech mortality has been greater than sugar maple mortality for several years. Sugar maple and beech were dominant in the understory although few stems <1 cm dbh were found near treefall gaps. Older gaps had more numerous and larger stems.

Currently, the structure and dynamics of the woods are very similar to other old-growth beech-sugar maple forests of the region. Beech is present in all size classes. However, the number of large beech stems has been declining steadily even though beech bark disease has not yet reached the area.

Tree stems were systematically sampled in 1983, 1988 and 1999 in a 1977 clearcut in the Pigeon River State Forest, Michigan. All stems were identified to species and recorded as living or dead and browsed or unbrowsed by mammalian herbivores, based on inspection of twigs and buds. Tree species richness increased in the study area, mostly due to the presence of several wind dispersed species previously not recorded. The abundance of all trees collectively declined over the study period as the clearcut aged and the relative abundance of the most preferred (and most common) browse species in 1983 declined to 0.0 by 1999. There was no evidence that mammalian herbivores were using the clearcut for feeding in 1999, suggesting decline of use as preferred species declined. About half the study area sampled in 1999 was dominated by herbaceous species, whereas the entire area was dominated by young woody growth in earlier years. The results collectively suggest that high degrees of sustained browsing affect community structure and composition by lowering abundance of more preferred species over time.

Patterns of leaf mass per unit area (LMA) and area-based foliar N concentration (N area) through the canopy were examined for seven tree species growing in reference and fertilized plots of two early successional northern hardwood stands in New Hampshire. Increases in LMA with height in the canopy were significantly related to increasing average daily photosynthetically active radiation (PAR). As expected, the slopes of regressions between LMA and PAR (i.e., plasticity) were higher for shade tolerant than intolerant species in both stands. Fertilization increased leaf area index in both stands. For the shade intolerant species (Prunus pensylvanica, Betula papyrifera), average canopy LMA increased in response to fertilization but no response was observed in the more tolerant species (Acer spp., Fagus grandifolia, Betula allegheniensis). The slopes of regressions between N area and PAR were highly significant, with higher plasticity of N area for shade tolerant than intolerant species. Average canopy N area increased in response to fertilization, and the response was particularly large for the intolerant species. The increase in N-area for these species was associated with the significant response of shaded foliage, as sun exposed foliage showed no response to fertilization.

Specific leaf area was measured for three dominant perennial grass species in a long term nitrogen fertilization experiment in an abandoned field in Minnesota. The specific leaf area differed among the species and increased with increasing levels of nitrogen fertilization. This increase in specific leaf area was up to 82% for Agropyron repens and shows that the response of specific leaf area to nitrogen fertilization can be highly plastic. Increasing specific leaf area within species, together with a species replacement, resulted in a 202% increase in leaf area index along the nitrogen gradient, whereas the biomass increased by only 57%. One-third of this increase was attributed to species replacement and two-thirds to the change in specific leaf area within species. This plastic response of specific leaf area within plant species substantially increases the aboveground competition for light along nitrogen gradients.

Desert grasslands that skirt mountain ranges in northern Mexico and the southwestern United States were once common. These grasslands have largely been replaced by shrublands and their soils have become eroded. The most frequently cited causes of these changes are livestock overgrazing, fire and increasing aridity. Studies have not separated grazing and fire from climate effects. Our aim was to determine whether desert grasses are being replaced by shrubs and how rapidly soil surfaces are eroding on unburnt Otero Mesa desert grasslands, where livestock overgrazing has not been a significant factor in historic or recent times. In this article we describe how vegetation and soil surface levels changed from 1982 to 1995 on six permanent transects. Vegetation was measured by charting canopy cover and stem bases of perennial plants in quadrats. Soil surface levels were surveyed in reference to benchmarks placed in nearby bedrock. Vegetation quadrats and surface levels were remeasured in 1995. From 1982–1983 to 1995 the canopy cover of the desert shrubs, Larrea tridentata and Gutierrezia microcephala, declined by 1.5% and 5.8%, respectively. Canopy cover of the C4 xeric grass Bouteloua eriopoda declined by 5.3%. This decline in xeric grass cover was offset by a 1.2% increase in the C4 mesic grass Bouteloua curtipendula and a 4.0% increase in the C3 mesic grass Stipa neomexicana. From 1983–1984 to 1995 soil surfaces along transects eroded an average of 0.4 mm·y⁻¹. Thus, desert shrubs were not replacing desert grasses, but mesic grass species were replacing xeric species. These changes were associated with a 15-y period of relatively wet cool-seasons and moist warm-seasons from 1981 through 1995. These results document that, even in the absence of livestock grazing and fire, desert grassland vegetation is very responsive to precipitation change over relatively short time periods.

Sporocarps of hypogeous mycorrhizal fungi (truffles) are the major food of northern flying squirrels (Glaucomys sabrinus). The two subspecies of northern flying squirrels that occur in the southern Appalachians, G. s. coloratus and G. s. fuscus, are endangered species which are primarily found in the ecotone between high-elevation spruce-fir and northern hardwood forests. Our objective was to determine the microhabitat and macrohabitat characteristics associated with the presence and abundance of truffles in suitable habitat for northern flying squirrels. We sampled for truffles in 24–26, 1-m² plots on each of 10 northern flying squirrel sites in North Carolina and measured micro- and macrohabitat characteristics associated with sample plots and sites. Elaphomyces granulatus was the most common species of truffle found (78.7%). Red spruce (Picea rubra) was significantly more likely to be one of the three closest trees to plots with truffles. Further, spruce was the most important species in plots with truffles, followed by beech (Fagus grandifolia), red oak (Quercus rubra) and yellow birch (Betula lutea), whereas the most important species in plots with no truffles were beech, followed by yellow birch, spruce and red oak. At the macrohabitat (site) level, spruce was the most important species in sites with high truffle production followed by beech and red oak, whereas the most important species in sites with low truffle production were beech, yellow birch, spruce and rhododendron (Rhododendron spp.). Significant variables entered into a linear regression model predicting the number of truffles in a site were the importance values of fir (Abies fraseri), spruce and silverbell (Halesia carolina). Our data suggest that spruce-fir or mixed spruce-fir/hardwood stands are important foraging sites for northern flying squirrels in the southern Appalachians.

Soil macrofauna (invertebrates >2 mm) were sampled for 3 y in 30 old growth and 13 second growth forest stands in eastern Kentucky. Macrofauna from 27 orders were collected. Mean macrofaunal dry weight was 912 mg/m² (n = 43, sd = 622) and did not differ significantly among the five landscape positions examined or between old growth and second growth forests. Approximately 95% of the macrofaunal biomass was accounted for by Coleoptera (beetle larvae), Oligochaeta (earthworms), Diplopoda (millipedes), Diptera (fly larvae), Chilopoda (centipedes), Araneae (spiders) and Formicidae (ants). There were no significant differences in the relative biomass of individual taxa between old growth and second growth forests. Earthworms were the only taxonomic group that differed significantly in dry weight per unit area among landscape positions, with greatest abundance on lower and protected slopes (x̄ = 695 mg/m², n = 10, sd = 744) and lowest abundance on dry south slopes, ridges and ravines (0–75 mg/m²). On average, earthworms accounted for 20% (n = 43,sd = 22) of the total macrofaunal dry weight, but were estimated to be dominant soil mixers on only about 23% of the study area. All earthworm species were indigenous to the study area; nonindigenous taxa were not observed in any invertebrate group.

Zebra mussels (Dreissena polymorpha) are beginning to colonize smaller inland lakes and streams in the eastern United States. To test the hypothesis that crayfish (Orconectes rusticus) could significantly reduce the recruitment of zebra mussels in streams, we conducted a replicated (n = 7) crayfish enclosure-exclosure experiment over 15 wk to simulate conditions during the early stages of a zebra mussel invasion. Four male O. rusticus were placed in each of seven enclosures (0.2 m²) each paired with an exclosure (week 0) in a small midwestern lake-outlet stream (mean width, 20 m) before zebra mussel settlement. At week 15 zebra mussel densities were 58% lower in enclosures than in exclosures (P < 0.05). Size frequency distributions did not differ significantly between treatments (P = 0.842; size range 1–10 mm in enclosures, 1–11 mm in exclosures). Densities (no/m²) of other macroinvertebrates did not differ significantly between enclosures and exclosures. Periphyton biomass was not significantly different between treatments, but macroalgal (Chara Nitella) biomass was present in exclosures [9 ± 7 g/m² (mean ± 95% CL)] and absent from enclosures (P < 0.001). These results suggest that streams with moderate to high densities of crayfish will experience slower invasion by zebra mussels, lower final densities of zebra mussels and lower abundance of macroalgae.

Laboratory experiments were conducted to determine the effects of various factors on interactions for refuge sites of two stream-dwelling benthic organisms. The effect of a piscivore, the smallmouth bass (Micropterus dolomieu), on intraspecific and interspecific interactions involving crayfish (Crustacea: Cambaridae: Cambarus longulus) and hellgrammites (Insecta: Megaloptera: Corydalus cornutus) was examined. Three possible interactions were recognized in all experiments: (1) the refuge occupant was evicted by an intruder; (2) the refuge occupant excluded the intruder from the refuge; (3) the occupant and the intruder shared the refuge.

The size of both crayfish and hellgrammites had a statistically significant effect on the outcome of interspecific and intraspecific interactions, larger individuals being more successful at excluding or evicting smaller individuals from a refuge. The effect of size on the interactions, however, was tempered by the effects of prior occupancy of the refuge (owner-intruder models), allowing smaller individuals of both species to maintain occupancy of the refuge when faced with a larger intruder in about one-third of all trials. There was no significant effect of gender on the outcome of interactions between male and female crayfish. The presence of a fish (Micropterus dolomieu) significantly altered the outcome of interspecific and intraspecific interactions. Not only were both species more likely to gain access to the refuge as an intruder, but the occupant was less likely to be evicted, resulting in a greatly increased incidence of sharing of the refuge in the presence of the fish. Refuge sharing by crayfish never occurred unless a fish was present. Refuge sharing by hellgrammites was an especially important interaction in the presence of fish.

Demographically complete sampling of a large population of Fusconaia ebena (Lea) in a mainstream shoal in the lower Ohio River (LOR) from 1983 through 1998 revealed two extremely successful recruitment years—1981 and 1990. Dominance of the 1981 and 1990 cohorts allowed length-to-age relationships to be estimated directly from length-frequency histograms. Two linear relationships adequately described growth rates from age 2 through 17 y. The first model applied to ages 2 through 10 y when annual growth averaged 6.1mm. The second model applied to ages 10 through 17 y when annual growth averaged only 1.1 mm. A survivorship curve was based on density of the 1981 cohort from age 2 through 17 y. During that period a constant proportion (17%) of the cohort died each year. Only 9% of the 1981 cohort alive in 1983 were still alive in 1998. In both 1981 and 1990 rapid and large spring rises in LOR discharge were immediately followed by rapid and large declines. These rises coincided with the expected spawning peak of Alosa chrysochloris, the only known fish host for F. ebena glochidia. The rapid return to low flow and depositional conditions was appropriately timed to enhance successful settlement of juvenile F. ebena after their parasitic stage on A. chrysochloris gills.

We examined the stomach contents of 374 eastern moles (Scalopus aquaticus) collected throughout the year from the Coastal Plain region of South Carolina. On average, stomach contents of males weighed significantly more than did those of females. Fifty-two different food items were recorded. The three most important foods were scarabaeid beetle larvae, ants and centipedes. Earthworms were observed in only 8.3% of the stomachs examined and represented only about 3% of the mean percent volume of the diet. Ants comprised 15.4% of the total volume. Twenty-nine species of ant were recorded; of these, four were taxa not previously reported to occur on the SRS. The imported red fire ant Solenopsis invicta was common within the study area; however, no individuals of this species were found in any of the mole stomachs.

Distributions of related species along environmental gradients provide ecologists with insights into factors that limit distributions of species. We apply this approach to two species of kangaroo rats. A survey in 1983 showed that Dipodomys merriami is replaced by D. panamintinus at the tops of elevational gradients in parts of the Mojave Desert where both species occur. Over the 17 y since the initial survey we have conducted six additional censuses along one such gradient. In years of high population densities D. merriami is more abundant at low and D. panamintinus at high elevations along this gradient. Following periods of drought, however, when population densities are reduced overall, D. merriami expands upward along the gradient, whereas D. panamintinus becomes restricted to even higher elevations. This pattern suggests that D. merriami normally is restricted to lower elevations by competition from the larger D. panamintinus, and experiences competitive release when the latter is at low density. The distribution of D. panamintinus, in contrast, responds to changes with elevation in primary productivity or in physical factors, rather than to competition from D. merriami. Because of relatively large body mass, individuals of D. panamintinus may be restricted to higher elevations, particularly in drought years, because primary productivity at these elevations suffices to support their metabolic requirements. This interpretation of limits to distribution has implications for conservation of these and similar species especially under impending climate change.

Effects of different types of human activity on populations of medium-sized mammals were examined by counting road kills in the Central Valley of California. The mean number of road kills recorded from July 1997 to August 1999 was 1.2/100 km, most being black-tailed jackrabbits (Lepus californicus). Road kills showed no marked seasonal trends. For some species habitat type influenced where carcasses were located, carnivores being found predominantly in rural habitats. For other species, such as Virginia opossums (Didelphis virginiana), domestic cats (Felis catus) and rats (Rattus rattus), carcasses were located in both rural and suburban landscapes. Some important assumptions notwithstanding road kill data can be effective in discerning how mammals are influenced by different types of land use.

Automatic cameras were used to record adult red-cockaded woodpecker (Picoides borealis) nest visits with food for nestlings. Diet of nestlings on or near an old-growth longleaf pine (Pinus palustris) remnant in southern Georgia was compared to that in longleaf pine stands established on old farm fields in western South Carolina. Diets of nestlings were expressed as percent nest visits and percent prey biomass. The method of calculating nestling diet composition had little effect on the relative ranking of prey. Roaches (Blattaria: Blatellidae) were the most common arthropod fed to nestlings, ranging from 33–57% of the prey brought to nest cavities by adults or 55–73% of the prey biomass. Other common prey were spiders, centipedes and caterpillars. The latter were primarily larvae of coneworms (Lepidoptera: Pyralidae, Dioryctria spp.) that bore into and feed on pine cones. Scorpions (Scorpiones: Buthidae, Centruroides sp.), an unusual prey, were recorded several times at the south Georgia location. Morisita's index (C) of diet overlap showed a high degree of similarity in nestling diets among years in the old-growth remnant (C = 0.91 to 0.94), as well as a high degree of similarity in the diets of nestlings among woodpecker groups within locations and between old-growth and old-field habitats (C = 0.89–0.95). Our study shows that old trees on relatively undisturbed sites provide the same prey as younger trees growing on old farm fields and the relative importance of the different prey was similar for both habitats.

With grassland bird populations in the Great Plains exhibiting steep declines, grassland managers require information on bird habitat needs to optimally manage lands dedicated to wildlife. During 1993–1994, we measured bird occurrence and corresponding vegetation attributes on mixed-grass prairie in northwestern North Dakota. Three hundred and ten point-count locations over a wide range of successional stages were sampled. Ten grassland passerine species occurred commonly (i.e., at >10% of point count locations), including two species endemic to the northern Great Plains [Baird's sparrow (Ammodramus bairdii) and Sprague's pipit (Anthus spragueii)], and several species of management concern [bobolink (Dolichonyx oryzivorus), grasshopper sparrow (Ammodramus savannarum), clay-colored sparrow (Spizella pallida)]. Some species were ubiquitous and had generalized habitat associations [e.g., savannah sparrow (Passerculus sandwichensis)]. Others exhibited more finely tuned, closely overlapping use of relatively short, sparse to moderately dense, grass- and forb-dominated habitat. We used logistic regression models to predict bird species' occurrence based on nine vegetation variables. Previously undefined limits of vegetation height and density were identified for Baird's sparrow and Sprague's pipit, and of shrub cover for Baird's sparrow. Our findings underscore the need for a mosaic of successional types to maximize diversity of prairie bird species. Managers may reduce confusion created by generic treatment prescriptions for grasslands by focusing on absolute rather than relative measures of vegetation, and by integrating standard data from multiple bird habitat studies across regions.

Historical and contemporary fish collection data were used to compare the relative abundance of introduced rough shiner (Notropis baileyi) in the Chattahoochee River (Halawakee and Mountain Oak creeks) to native populations in the Tallapoosa River and to examine the effect of the introduction on the native Chattahoochee River fish community. Absent during the 1981–1985 survey of Mountain Oak Creek, the rough shiner was the fourth most abundant species (10.5% of catch) taken in 1995. In Halawakee Creek mean relative abundance of rough shiner increased from 9.8% in 1971 to 19.8% in 1995. The rough shiner was not collected above the milldam in Halawakee Creek during the historical and contemporary surveys. The rough shiner tended to be more abundant in Halawakee Creek than in its native Tallapoosa River (t = −2.11; df = 11; P = 0.06), where species richness is higher. In Mountain Oak Creek, blacktip shiner (Lythrurus atrapiculus) and golden shiner (Notemigonus crysoleucas) were abundant historically, but were not taken during the contemporary survey. Their absence, however, was not due to the introduction of the rough shiner. Faunal similarity (relative abundance of the 15 most common species) over time was high in Halawakee (Morisita's Index; I_m = 0.85) and Mountain Oak creeks (I_m = 0.70). These findings indicate that species-rich fish communities can adjust to enrichment with minimal impact on native species. Despite having little effect on overall community structure (I_m values over 0.70), the rough shiner appears to be contributing to changes in the relative abundances of two resident species (bluehead chub, Nocomis leptocephalus; weed shiner, Notropis texanus). The relative abundance of bluehead chub, a nest-associate with rough shiner, increased significantly following the introduction of rough shiner to Mountain Oak Creek. Abundance of weed shiner decreased sharply in both Halawakee and Mountain Oak creeks. The significant negative correlation (r = −0.46; P = 0.03) between relative abundances of rough shiner and weed shiner suggests that the rough shiner is limiting weed shiner through competition for food or habitat.

We examined plant climbing by the common striped scorpion Centruroides vittatus to determine which of two hypotheses (the predation avoidance hypothesis or the increased prey availability hypothesis) best explained this behavior. In the field we observed nocturnal scorpion activity for 16 mo during 1992–1993 to quantify climbing behavior and collected data on potential prey abundance on the ground and in vegetation for 5 mo. We also performed a laboratory experiment examining the effects of hunger level on scorpion climbing and activity. Individuals found up in vegetation accounted for 19.3% and 25.2% of scorpions active in 1992 and 1993, respectively. Juveniles were significantly more likely to be found in vegetation than were adults in both years, although juveniles and adults did not differ in the proportion found carrying prey in vegetation. We found significant seasonal variation in prey abundance, with prey density being greatest in September. Prey density was also significantly greater on the ground than in vegetation when all trapped invertebrates were included; however, when we excluded collembolans because of their small size, this difference was no longer significant. Laboratory results indicated that there were no within-treatment differences among age classes/sexes in any behavior (climbing frequency, activity level or maximum height climbed). When hungry, males (but not females or juveniles) climbed higher and juveniles (but not adults) were more active. Hunger level had no effect on climbing frequency for any age class/sex. In combination, the field and laboratory data are most consistent with the predation avoidance hypothesis as the main reason for plant climbing by scorpions.

White-tailed deer (Odocoileus virginianus) were videotaped depredating four songbird nests in grassland habitats in southeastern and northcentral North Dakota, 1996–1999. Deer ate two Savannah sparrow (Passerculus sandwichensis), two grasshopper sparrow (Ammodramus savannarum), one clay-colored sparrow (Spizella pallida), one red-winged blackbird (Agelaius phoeniceus) and three brown-headed cowbird (Molothrus ater) nestlings. Deer removed nestlings quickly (5–19 sec/nest) at night (22:00 to 05:17 Central Daylight Time) and left no evidence of predation. Although probably opportunistic, deer predations clearly were deliberate and likely are more common than generally believed.

Ozark bass (Ambloplites constellatus) are endemic to the White River drainage in northern Arkansas and southern Missouri. Although they are assumed to be similar to rock bass (A. rupestris), little is known of their behavior or life history. We investigated the spawning behavior and ecology of Ozark bass by snorkeling and seining in the Buffalo National River, Arkansas, from 1990–1992. Most males nested on gravel or cobble substrates. In 1992 65% of nests occurred within 1 m downstream of cover. Egg deposition was asynchronous, but began when water temperatures reached 17 C. Embryos hatched in 5 d at a mean water temperature of 21 C and free-embryos remained in their nests for up to 9 d before swim-up. Predation and high water limit Ozark bass spawning success in the Buffalo River. No nests in our study area successfully produced dispersing young in 1991, while 10% of nests monitored in 1992 were successful. Young-of-year were difficult for divers to locate during the day in 1990–1992 and were caught in seine hauls at night, but not during the day, suggesting that they may be nocturnal at this stage.

We used VHF, GPS and satellite radiocollars to study details of long distance movements by four Minnesota wolves (Canis lupus). Number of locations during our tracking ranged from 14 to 274. Farthest distances reached ranged from 183–494 km, and minimum distances traveled (sums of line segments) ranged from 490–4251 km. Numbers of times wolves crossed state, provincial or interstate highways ranged from 1 to 215. All four of the wolves returned to or near their natal territories after up to 179 d and at least two left again.

Four species of sympatric metamorphosed desmognathine salamanders collected from southern Appalachian mountain streams in western North Carolina were examined for the presence of the glossiphoniid leech, Oligobdella biannulata. Leeches were most frequently observed on Desmognathus quadramaculatus (prevalence and mean intensity = 22.6% and 2.8 ± 2.1, respectively). The largest leech infrapopulations (≥5 leeches/host) were observed on the largest individuals of D. quadramaculatus with 45.6% of the leeches observed found on five hosts, all of which were >82 mm SVL. The larger body size and more aquatic habitat requirements of this species, relative to Desmognathus monticola and D. ochrophaeus, increases the potential for transmission of leeches. Leeches were not found on the most aquatic salamander, D. marmoratus, nor the most terrestrial congener, D. ochrophaeus. The former species inhabits strong currents in streams; a habitat possibly limiting leech attachment and prolonged feeding. Leeches showed a pronounced seasonality, with 96% of leeches observed on D. quadramaculatus collected during May, June and July (maximum prevalence and mean intensity on D. quadramaculatus was 67% and 3.9 ± 2.8, respectively). Trypanosomes were most prevalent in the blood of D. quadramaculatus (28%). This may result from greater exposure to blood feeding by O. biannulata, the only leech species ever observed on these salamanders, and, thus, the presumed vector for trypanosome transmission.

Habitat selection by ant queens has been little studied even though it may be a critical component of colony founding. We describe the movement pathways of honey ant queens (Myrmecocystus mimicus Wheeler) searching for sites on the ground to initiate nests. Typical paths may include segments of directional movement that are interrupted by segments of area-restricted search. Mechanisms producing area-restricted search might include variable step lengths and looping behavior. Cues that prompt the switch to local search remain undetected.