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Presence and frequency of epiphytic macrolichens were measured along an air-quality gradient in Halifax City, NS, Canada. Species frequency plots over distance and multidimensional scaling (MDS) suggested lichen-community changes consistent with expected air-quality changes. A provisional list of air-quality indicators was selected based on: 1) demonstrated variation along the air-quality gradient, 2) frequency across the province, 3) literature values of air-quality sensitivity, and 4) ease of field identification. Indicators were placed in one of three classes: 1) pollution tolerant, 2) intermediate pollution tolerance, and 3) pollution sensitive. MDS analysis suggests an elevation gradient in Nova Scotia and this should be investigated with a further study.
Species richness of corticolous macrolichens was monitored at one- or two-year intervals on a total of 63 plots from 1997–2003 in a region of west-central Pennsylvania that included four coal-fired power generating stations and an industrial city. Lichen richness significantly increased from an average of 5.7 species/plot in 1997 to 9.3 species/plot in 2003. A linear mean rate of gain in species on regional monitoring plots was 0.56 species/yr. Plots along a major ridge top had a slower but significant gain in richness, and a localized area flanked by the city and two generating stations exhibited less lichen recolonization. Our results confirm the value of macrolichens as indicators of air quality and the importance of examining temporal as well as spatial changes in lichen richness to ascertain air-quality status.
The epiphytic corticolous moss Dicranum montanum, a common inhabitant of upland Quercus rubra (northern red oak) trunks in southwestern Pennsylvania, is a useful biomonitor to evaluate levels of total mercury (Hg) in stemflow within mixed-oak forests. Moss samples were collected annually during October–November of 2000–2005 at 11 permanent research plots on a ridgetop and analyzed for total-Hg concentrations. The mean total-Hg concentration in moss tissue across all 11 plots for all 6 years (n = 66) was 424 ng/g dry wt. Total Hg for 9 of the 11 plots exhibited a downward time trend during the 6-year period; the trend line for the remaining two plots was nearly horizontal. When all data were combined, the linear regression based on mean Hg values for all plots was significant at p = 0.028 over the 6-year study period, with an adjusted R-square of 67.6%. This downward trend likely reflects reduction of airborne Hg emissions in the region due to several factors, including closure of steel mills and coke ovens in the Johnstown–Pittsburgh area, co-benefit of sulfur dioxide emissions controls, and reduction of Hg emissions from municipal and hospital incinerators.
Pre-settlement barrens of Illinois were fire-maintained communities with an open tree canopy and a grass-dominated ground layer. Found on rolling topography, they were commonly underlain by well-drained, nutrient poor, clayey soils. Fire suppression following the arrival of the European settlers resulted in canopy closure and the loss of many prairie species that once dominated the ground layer. Both barrens studied had closed canopies due to decreased fire frequency, though both are currently being managed by fire. Quercus alba (white oak) and Q. stellata (post oak) dominated the overstory and accounted for more than 50% of the importance value. Very few shrubs, woody seedlings, and saplings were present, probably due to recent fires. Stephen A. Forbes State Park Barren in Marion County had been subjected to one burn before the study, and few prairie species were present there. The Buhnerkempe Barren in Clay County was subjected to occasional burns prior to our study and had higher prairie species diversity.
The purpose of this study was to analyze ice damage to 228 trees of 9 species on the Virginia Tech campus. Damage was caused by three severe ice storms in February and March 1994. There were significant differences among species in amount of damage. Four ways of expressing percent damage were compared (% individuals damaged, % basal area of damaged trees, % crown damage, and an average of the three). The average method yielded the most significant comparisons, followed by percent crown damage. The species, ranked in four groups by mean total damage, are as follows: most damage (Acer saccharum, Chamaecyparis nooktakensis, Ulmus americana, and Acer nigrum: 29.7–26.4%); less damage (Quercus alba and Platanus occidentalis: 18.4–13.7%); lesser damage (Cornus florida: 10.2%); and least damage (Quercus rubra and Quercus palustris: 6.7–0%). The differences among groups were significant at P ≤ 0.05. Ice damage also caused a significant decrease in crown growth of four species. Comparisons with other studies revealed good correspondence, in general, with two or three exceptions. Our conclusions are that three factors were chiefly responsible for the relatively severe damage to trees: 1) the severity of the ice storms; 2) the open, exposed siting of all the trees, similar to trees growing at the edge of a forest; and 3) the high percentage of large trees with internal decay and asymmetric crowns.
We studied the effects of browsing by Odocoileus virginianus (white-tailed deer) on the native and non-native vegetation in a mixed oak-beech forest in Rock Creek Park, Washington, DC. We compared the thickness and cover of vegetation up to 2 m in height, and species richness of native and non-native plants in 17 exclosed (1 × 4 m) and 17 control plots from 2001–2004. Over the four-year period, foraging by deer suppressed the thickness of vegetation ≤ 1 m in height, reduced the cover of herbaceous, woody, and native plants, and generally decreased the species richness of native and woody plants. Browsing had no effects on the species richness of non-native plants, but generally reduced the prevalence of Celastrus orbiculatus (oriental bittersweet). Of the dominant canopy species, browsing affected Quercus spp. (oak) regeneration, but had no apparent effects on Fagus grandifolia (American beech). These results indicate that white-tailed deer are having a detrimental effect on the structure and species richness of native plants in this forest, and as a consequence, diminishing the value of the habitat for wildlife. In addition, white-tailed deer may help control the spread of oriental bittersweet in forest interiors, particularly where this species occurs at relatively low levels. If deer browsing is left uncontrolled in this forest, we predict that its future composition will shift towards one with fewer species and one dominated almost exclusively by American beech.
To assess the community-level responses of a New England forest to invasion by the Eurasian biennial Alliaria petiolata (garlic mustard), we conducted a vegetation census at twenty-four plots ranging from low to high invasive cover, and experimentally removed 0, 50, or 100% of garlic mustard from adjacent highly invaded plots at the same study site. Species richness did not respond to natural or experimental levels of invasion, but the Shannon diversity and equitability indices declined with increasing in situ densities of garlic mustard, and increased in response to removal of garlic mustard at the experimental plots. Individual species demonstrated variable responses to high-, intermediate-, and low-level invasion. Of all plant functional groups, tree seedlings declined most notably with increasing in situ levels of invasion. This functional group, and seedlings of three key canopy tree species within the group, increased in response to partial, but not full eradication of garlic mustard. Our results demonstrate that the effectiveness of full or partial removal depends on management priorities for promoting overall diversity, species richness, native species composition, and/or individual species performance within native communities.
To determine if the quality of winter diet is related to winter-habitat sexual segregation, Lagopus lagopus L. (Willow Ptarmigan) were collected in three wintering areas of Labrador between December and April 1998–2000 (n = 310). Crop contents were used to evaluate diet differences according to sex, age, and area. The most prominent item in ptarmigan crops was Salix spp. (willow; range 45–89%). The crops of adult females contained approximately 60% more willow, the most nutritious food in their diet, and 45% more calories than those of adult males. All birds collected from western Labrador contained more willow twigs and buds and more calories than those collected in central or eastern Labrador. The Gardarsson hypothesis suggests that males winter adjacent to breeding areas to improve competition for territories, and females choose areas with greater abundance and quality of food to enhance reproductive success. We could not reject this hypothesis since the wintering site with the most female-biased sex ratio was where diets had the greatest mass of willow and total calories.
The purpose of the study was to estimate seasonal home ranges of Sylvilagus obscurus (Appalachian cottontail) within dense ericaceous and coniferous cover at its type locality, the Dolly Sods Scenic Area in West Virginia. Ninety-five percent adaptive kernel (AK) home ranges of rabbits ranged from 5.7–13.3 ha during the leaf-on season (May–September; n = 5) and 1.5–9.0 ha during the leaf-off season (October–April; n = 14). Fifty-percent AK core areas ranged from 0.9–2.5 ha during the leaf-on season and 0.1–2.5 ha during the leaf-off season. Males occupied larger home ranges during the leaf-on than leaf-off season, but female ranges did not differ seasonally. These results demonstrate seasonal differences in spatial and associated resource requirements of Appalachian cottontails and the need for large tracts of appropriate habitat for travel lanes to maintain viable populations of this species.
Contrary to previous literature concluding that body size of Canis latrans (coyotes) does not increase in North America with decreasing longitude, this study presents data from different regions and concludes that northeastern coyotes are the largest extant version of coyote. Male coyotes from northeastern North America (16.4 ± 1.5 [SD] kg, range = 14.2–20.4) were heavier than females from the northeast (14.7 ± 1.6 kg, range = 11.9–17.9) and were also heavier than male (10.6 ± 1.0 kg, range = 8.8–12.0) and female coyotes (12.1 ± 1.1 kg, range = 10.5–14.1) from outside of the northeast. Female coyotes from northeastern North America were heavier than all male and female western coyotes. Longitude was significantly correlated in both male (r = − 0.786, P < 0.0001) and female (r = − 0.769, P < 0.0001) body mass, whereas there was less of a correlation for latitude and body mass for males (r = 0.355, P = 0.043) and females (r = 0.364, P = 0.044). Sixty-two percent (P < 0.0001) and 59% (P < 0.0001) of variation in body mass of males and females, respectively, could be explained by longitude, while 13% (P = 0.043 for males; P = 0.044 for females) could be accounted for by latitude.
We sampled 9 sites (5 free-flowing and 4 impounded) to investigate effects of lowhead dams on the habitat characteristics and the freshwater mussel assemblage of the Fox River in Illinois. We used 2 habitat indices, the Qualitative Habitat Evaluation Index (QHEI) and the Stream Habitat Assessment Protocol (SHAP), to determine effects of lowhead dams on habitat quality. Free-flowing sites had higher QHEI and SHAP scores than impounded sites, indicating higher quality stream habitat. We calculated 3 variables, catch-per-unit-effort (CPUE), extant species richness, and percent missing species, to establish effects of lowhead dams on freshwater mussels. Free-flowing sites had higher CPUE and extant species richness and lower percent missing species than impounded sites. We also examined literature reviews and museum collection holdings to determine species distributions within the basin. These data suggest that dams limit the upstream distribution of 5 species.
The termites Reticulitermes virginicus and R. flavipes are sympatric in forests along the eastern United States from Florida to Maryland. These congeners construct subterranean nests, forage on surface and buried wood, and appear to have very similar ecological requirements. In the present study, I examined host-wood selection by these species in a coastal forest over two years. Logs inhabited by R. virginicus had significantly greater diameters than those used by R. flavipes. It is not known whether this pattern resulted from species-specific differences in preference for host size or competition for preferred logs. Host-wood temperature did not differ for R. virginicus and R. flavipes.
A Turdus migratorius (American Robin) nest was found in southern New Brunswick, Canada, containing 52 mature sporocarps (“truffles”) of Elaphomyces granulatus (false truffle), a species of hypogeous fungus common across North America. Teeth marks on the truffles indicated they had been cached in the nest by a Tamiasciurus hudsonicus (red squirrel). The truffles appeared to have been air-dried before caching and were well preserved. Mean (± SD) weight of each truffle was 3.3 ± 1.4 g, with a total weight of cached material of 173 g. Although caching of epigeous fungus by squirrels is well documented in the literature, records of cached hypogeous fungi are relatively uncommon, and caches involving disused bird nests appear to be rarely encountered.