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The hydrogeomorphic approach, which assesses a wetland's geomorphic setting, water sources, and hydrodynamics, has proven to be a useful framework for characterizing wetlands. Yet, estimating wetland water sources quantitatively across more than a few study sites remains impractical for larger comparative studies due to the time-intensive measurements required. In this research we tested the efficacy of using dissolved magnesium (Mg2 ) as a semiconservative tracer of wetland water sources in southern Lower Michigan. Because concentrations of magnesium in groundwater are high due to equilibrium with dolomite in the glacial deposits, dissolved magnesium distinguished the relative importance of groundwater vs. precipitation as wetland water sources. We examined a set of 24 wetlands to consider relationships between a wetland's water sources and its geomorphic setting, water level variation, and biogeochemistry. Fens and swamps were generally groundwater-dominated, whereas wetlands dominated by Sphagnum mosses (“bogs”) were all strongly precipitation-dominated; few wetlands exhibited relatively equitable contributions of groundwater and precipitation. In terms of geomorphic setting, precipitation-dominated acidic bogs were restricted to isolated basins that were positioned higher on the landscape. In contrast, groundwater-dominated circumneutral fens and swamps occurred in basins that spanned the range of landscape position and were associated with surface inlets and outlets. Mean and maximum water levels were lower in more groundwater-dominated wetlands associated with outflow streams. Mean nutrient (ammonium and phosphate) availability was generally higher in more groundwater-dominated wetlands, whereas all precipitation-dominated wetlands had low nutrient availability. We conclude in the southern Great Lakes region: (1) dissolved magnesium can be used to characterize wetland water sources, and (2) the relative importance of groundwater vs. precipitation is strongly linked to a wetland's geomorphic setting, water level variation, and biogeochemistry.
A vector of multiple arboviruses, the invasive Asian tiger mosquito Aedes albopictus was recently found to develop inside the pitchers of the purple pitcher plant Sarracenia purpurea in a forested environment. In this study larvae and pupae of Ae. albopictus were found in S. purpurea pitchers in a peridomestic habitat in central North Carolina. Evidence of direct oviposition on the inner sides of the pitchers was obtained by dissecting pitchers and examining the insides for eggs, which were then raised to adults. To determine if pitcher size and origin (same or different plant) affected the presence of immature Ae. albopictus, these variables were measured and compared against the presence/absence of larvae and/or pupae through a logistic regression analysis. Statistical evidence showed pitchers with larger openings were much more likely to contain larvae and/or pupae, and pitchers from the same plant were not significantly more often colonized than pitchers on other plants. These data, in combination with the presence of dead adult females in pitchers, suggest the morphology of some pitchers may prevent successful oviposition by gravid females.
Semi-natural grasslands are a crucial habitat for many butterfly species and the structure and extent of that grassland often dictates the composition of butterfly communities on the landscape. To understand effects on butterfly communities, we studied the impacts of different management schemes used to maintain semi-natural grasslands, including mowing every 3 y, mowing annually, and continuous summertime grazing. Transect count data were gathered over the 3 summers (2007–2009) in the Southern Appalachian Mountains of western Virginia and North Carolina. Eleven thousand two hundred and four butterfly individuals of 42 different species were documented over the course of the study. Fields with minimal management, being mowed only once every 3 y, had the largest benefit to butterfly communities. Species richness, abundance, and Shannon diversity was significantly higher in these fields. While abundance was not significantly different between annually mowed fields and grazed fields, mowed fields were significantly higher in richness and diversity. The analysis of habitat specialist species revealed minimally managed and mowed fields were higher in abundance and richness than grazed fields. The response of individual butterfly species also showed negative effects of grazing on habitat specialists. Overall, the results suggest a varying response by different groups of species as well as individual species, indicating multiple management techniques are necessary for conserving a wide range of species. Specific techniques can be used in conservation to target specialist groups of butterflies and rare species.
We investigated fruit set, seed set, and germination requirements of shrubby reed-mustard (Hesperidanthus suffrutescens), an endangered endemic shrub in the Uinta Basin of eastern Utah, U.S.A. To determine the degree of self-compatibility, 120 plants received four pollination treatments each for 2 y. Treatments included autogamy, geitonogamy, xenogamy, and an open control. Autogamy and geitonogamy produced substantially and significantly fewer fruits, seeds, and seeds per fruit than xenogamy, suggesting little self-compatibility. Additionally, the maternal reproductive success of outcrossed flowers was significantly greater than open control flowers suggesting pollen limitation, perhaps due to reduced pollinator abundance or activity. One study population showed significantly reduced reproduction during the second year, perhaps resulting from impacts of anthropogenic disturbance. Although both selfing treatments produced significantly fewer seeds, there were no significant differences in germination among treatments. Potential pollinators were observed and collected during three sampling efforts. A total of 77 flower visitors were collected during the study. Potential pollinators providing outcrossed pollen included several Andrena species and several Lasioglossum and Halictus species. Overall, these results indicate little self-compatibility while suggesting that the pollinators needed for successful reproduction may, in fact, be limiting. This study highlights the important role of native pollinator fauna in conservation while providing managers with the basic reproductive ecology needed to conserve this endemic desert shrub.
Encroachment of woody species is a significant threat in native grasslands. This study exams the interaction between shrub-sapling overstory and ground layer species and functional group (FG) cover, richness, and diversity along a woody encroachment gradient. The study area is a 65 ha mosaic of tallgrass prairie and shrubland in northeastern Illinois. The study questions were: (1) how do plant species and FG cover, richness, and diversity respond to increasing levels of woody encroachment, (2) are there levels of encroachment relevant to restoration opportunities, and (3) are there patterns of FGs associated with increasing levels of encroachment that can serve as ecological indicators? Data on ground layer and overstory structure including stem density, canopy cover, and leaf area index (LAI) were recorded; LAI explained the most variance in the ground layer data.
There was a significant decline in several ground layer species and FG parameters with increasing woody encroachment (LAI) and percent bare ground increased. For most parameters, change followed a linear response; however, native species diversity and FG density declined only after LAI reached intermediate levels and the changes are best fit by a quadratic function. Cover and species richness of perennial dicot (PD) forbs, C3 and C4 grasses, legumes and hemi-parasites declined with increasing LAI. Native FGs most strongly associated with the lowest LAI levels were hemi-parasites, C4 grasses, legumes, and PD forbs. Efficacious opportunities for restoration remain at this site following low-to-intermediate levels of woody encroachment and results highlight ordered patterns of decline in cover and richness of FGs that may guide evaluating restoration potential of sites undergoing woody encroachment.
Resprouting is advantageous for plants in pyrogenic ecosystems because it allows for quick re-acquisition of space after fire. Resprouting species build multiple stems during their lifetime and have an established root system, which may affect growth and biomass allocation and whether resprouts conform to predicted scaling relationships. We measured height, basal diameter, and biomass of stems of five resprouting shrub species in scrubby flatwoods sites in Florida, varying in time after fire (6 w, 1 y, 8–9 y, 20–21 y). Differences among species in size and allocation ratios tended to be greater in recently burned sites. Six weeks after fire, the dominant species, Quercus inopina, had the highest height∶diameter and leaf∶stem biomass ratios, which may contribute to the ability of this species to persist over fire cycles. The slope of the relationship between stem height and diameter was higher in recently burned sites than 8 to 21 y after fire, whereas the slope of the relationship between stem height and biomass was higher 8 to 21 y after fire than in recently burned sites. Height and biomass of resprouts generally scaled differently with respect to diameter and height than predicted by allometric theory, but biomass of resprouts, on average, scaled with diameter as predicted. Therefore, resprouted stems were taller for a given diameter and accumulated less biomass with height growth. In pyrogenic ecosystems, it may be more advantageous to grow tall, to maximize light capture, than to invest in strength to avoid damage because fire will eventually remove stems. Our results indicated that current allometric theory does not adequately represent scaling of growth and biomass of resprouting shrubs.
Pine forests have historically been an important component of Great Lakes coastal ecosystems that provide wildlife habitat and other ecosystem functions. The area covered by coastal forests and the dominance of pines within remaining forests have been greatly reduced over the past ∼200 y by logging, development, and other anthropogenic activities. This study assessed stand history and composition of remnant coastal pine forests and compared contemporary stands to historical baselines to support restoration efforts in these ecosystems. Sampling was conducted in 23 stands at eight sites along the shores of Lakes Michigan and Superior in Michigan, U.S.A. and was focused on stand composition, age structure, and disturbance history. Current data were compared with data from presettlement Public Land Survey records in coastal pine forests across the region. Composition in contemporary forests differed greatly from presettlement conditions in southern sites and was significantly, but not as strongly, different in the northern part of the region as well. Pine dominance in remnant stands was lowest with moderate levels of pine-logging-era canopy removal. Comparisons of overstory and understory dominance suggested a continued trend away from pine dominance toward mesophytic species in all stands. Restoration of disturbance regimes (particularly surface fires) and open canopy conditions may be necessary to maintain a pine component in these ecosystems.
Forest fragmentation threatens the reproduction of tree species, for which habitats overlap with urban and rural areas. An endangered maple, Acer miyabei f. miyabei, is such a species in northern Japan. We examined the effects of forest fragmentation on seed production and mate diversity and assessed gene flow within and between fragmented forests. We measured the density, viability, and kinship of seeds dispersed around 82 target trees in 21 fragmented forests in rural and urban areas. The dispersed seed density decreased as the size of the target trees and the number of adult trees in each forest decreased. The viable seed proportion also decreased as the number of adult trees in each forest decreased. We did not find any effects on the kinship co-efficient among seeds dispersed around each target tree. The regression line of the pairwise kinship co-efficient of the seeds against the distance had a higher intercept and a more gently declining slope between the forests than within the forests, indicating forest fragmentation altered gene flow patterns. The results suggest reduced seed production due to pollen limitation and changes in the genetic structure of regenerating populations of A. miyabei in fragmented forests.
Wind energy development is rapidly expanding globally, as are concerns about the potential threats wind facilities pose to bird and bat populations. To date, many studies have explored the direct impacts of wind turbines on wildlife, such as wildlife-turbine collisions, but few have addressed indirect impacts, such as habitat degradation. These potentially subtle impacts can have far reaching effects on the abundance, distribution, survival, and breeding success of wildlife. We conducted a study to assess whether proximity of wind turbines to shrub-nesting birds influenced rates of nest failure associated mainly with depredation and brood parasitism by Brown-headed Cowbirds (Molothrus ater). During the primary nesting period of five passerine species, we monitored 253 active nests. We used a logistic-exposure method to model nest fate as a function of the important variables identified (including distance from turbine and brood parasitism). Our results indicate little relation between nest success and distance to turbine, with one exception, the Blue-gray Gnatcatcher (Polioptila caerule). For this passerine, we found nests closer to wind turbines had a lower probability of being brood parasitized and subsequently had higher nest success rates. We recommend future studies explore the potential implications of wind energy development on brood parasites, such as the Brown-headed Cowbird. As there is regulatory and social pressure to devise management strategies that reduce the impact of brood parasites on species of concern, any opportunities to decrease the risk of brood parasitism could be of benefit.
Body mass – gut fill scaling relationships affect rate of digestion, foraging behavior, niche differentiation, and trophic interactions. On an intraspecific level, the scalar of this relationship has been reported to be both iso- and allometric (<1.0). We hypothesized the scalar of rumen-reticulum fill depends on diet. When the diet has low concentrations of indigestible fiber the scalar should be allometric to fulfill metabolic demands and isometric when the diet has high concentrations of indigestible fiber as both small and large animals have difficulties processing forage. We collected 50 male and 50 female white-tailed deer (Odocoileus virginianus) over a 30 h period from a site in south Texas in Oct. Animals ranged in body mass from 32 to 106 kg. We also recorded collection time, sex, lactation status of females, back fat thickness, and tooth wear. These covariates affected the body mass – rumen-reticulum fill relationship. Acid detergent fiber, our surrogate of indigestible fiber, in the rumen contents of our study animals was lower in concentration than in another study of white-tailed deer that estimated an isometric scalar for rumen-reticulum fill. The estimated scalar between body mass and rumen-reticulum fill in our study was 0.74 and allometric. Rumen-reticulum fill probably was influenced by chemostatic feedback and mechanisms were governed by metabolic demands. Rumen-reticulum fill scalars for white-tailed deer are not static but dynamic.
Reproductive parameters and estimates of population size of northern river otters (Lontra canadensis) are poorly documented in southeastern United States. We examined the current population status of river otters in Kentucky, reintroduced in 1991 to 1994, by deriving demographic and reproductive characteristics from necropsies of river otter carcasses collected during harvests in Nov. through Feb., 2006–2009. We derived age distribution, sex ratio, pregnancy rate, and litter size of river otters and used these data to model future population growth of river otters in Kentucky. Data indicate 35.7% of female river otters in the yearling age class showed evidence of reproductive activity. The pregnancy rate (0.72) and average litter size [3.14 ± 1.46(sd)] of adult females was high compared with values reported for established populations of river otters elsewhere in eastern North America; consistent with an expanding and successfully recolonizing population. The population age distribution was skewed toward young age classes, with sex ratio of juvenile animals (1.58∶1.0) significantly favoring males. Models demonstrated the most plausible population growth estimates when using a 5% additive mortality factor, with extinction a possibility at lower published annual survivorship rates (below 0.73). Our data support a conservative harvest rate for sustained long-term management of river otters in Kentucky, especially for the eastern mountain region.
Silvicultural disturbance can lead to major shifts in biotic and abiotic characteristics of forests, with significant implications for wildlife. Many studies have demonstrated site occupancy and abundance of small mammals changes following silviculture, but few have identified the habitat characteristics associated with small mammal responses. We conducted a study in the central hardwood forest region of the U.S. to examine the relationship between small mammal habitat use and habitat variables at the microsite scale, before and after silvicultural disturbance, while explicitly accounting for imperfect detection. Following the creation of harvest openings, vegetation cover and coarse woody debris increased, and leaf litter depth decreased. Fewer changes occurred following the midstory removal stage of a shelterwood harvest. Eastern chipmunks (Tamias striatus) and white-footed mice (Peromyscus leucopus) were positively correlated with woody vegetation cover and coarse woody debris, and short-tailed shrews (Blarina brevicauda) were positively correlated with coarse woody debris and leaf litter depth. Careful consideration of experimental scale and incorporation of detection probability are necessary for successful identification of small mammal associations within microhabitats, as these relationships help to explain shifts in small mammal communities following silviculture.
Tree squirrels are known to communicate with their tails, but the only aspects of this communication that have been studied are tail flicking and piloerection. We investigated the communicative significance of tail position in wild eastern gray squirrels (Sciurus carolinensis) by videotaping tails on squirrels at an artificial food source. We determined the relative dominance ranks of each individual in each video clip. Each time one squirrel approached another, we recorded the degree of aggression exhibited by the more dominant individual, as well as two variables describing tail position (tightness of curvature and portion of tail bent) for each squirrel. Both tail position variables and their interaction effects significantly predicted the dominant squirrel's degree of aggression in a multiple regression analysis, suggesting tail position communicates information related to aggression in eastern gray squirrels.
The relationship between the patterns present on the pronotum and the elytra of the multicolored Asian lady beetle Harmonia axyridis was investigated. In males elytron size was a significant predictor of pronotal intensity and in females the fraction of the pronotum covered in black was related to their elytral spot brightness. Other significant sex differences included females having more of their pronota covered by melanins and the pigments deposited there being more intense than in males. The potential significance of these sex differences is discussed as well as the potential for these signals to serve in a mate choice context.
We report a population of Bigeye Shiner Notropis boops in the South Fork Hughes River drainage of the Little Kanawha River, West Virginia. A total of 27 individuals of N. boops were collected during five sampling efforts from 1999 to 2005. These specimens represent an addition to the state fauna, a distributional record for the Little Kanawha River, and an eastern range extension for this species on the Appalachian Plateau, West Virginia. Notropis boops in the South Fork Hughes River drainage likely represents a native population.