SWS Abstracts
Oral Presentation
Student Presentation:
Yes
Presenting Author:
Carly Eakin, Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; carly.eakin@maine.edu
Additional Author(s):
Aram Calhoun Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; calhoun@maine.edu
Malcolm Hunter Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; mhunter@maine.edu
Abstract Body:
Vernal pool-breeding amphibians are threatened by habitat degradation associated with urbanization. Land use change near pools can alter conditions that influence larval development and, via carry-over effects, adult survival and reproductive success. Better understanding amphibian responses in urbanizing landscapes may help guide conservation of these amphibians in developing landscapes. In 2014-16 we surveyed pool characteristics and wood frog (Lithobates sylvaticus) reproductive effort, larval development, and larval abundance at 35 pools across the urbanization gradient near Bangor, Maine, USA. Additionally, we used GIS to quantify impervious, forest, and water cover within 1,000 m of pools. We used regression tree analyses (RTA) to identify the importance of landscape and pool characteristics in explaining variation in larval condition and developmental rate (both adjusted for developmental stage and Julian day) and survival. We created partial dependence plots to examine the influence of important predictor variables. RTA explained 47% of the variation of larval development rate, with higher than expected development rates associated with pools with > 5% impervious surface within 300 m and pools with short hydroperiods. Tree cover within 1,000 m of pools was an important for partitioning pools; i.e., pools with ≤ and > 52% tree cover within 1,000 m had higher and lower than expected development rates, respectively. RTA explained 17% of the variation of relative survival and identified hydroperiod length as positively associated with relative survival, with the highest survival for pools drying mid-July or after. RTA was not effective in explaining variance of larval condition. Our results suggest that land cover change, as measured by impervious surface and tree cover at large scales (300–1,000 m), could increase larval developmental rate. Faster developing wood frog larvae have lower survival and fecundity as adults, thus land conversion at these scales could be detrimental their populations. Low relative survival at pools with shorter hydroperiods indicates the sensitivity of wood frog larvae to the duration of inundation in pools without predatory fish. Because of the high variability within these data and the relatively low-levels of urbanization near Bangor, we caution that these emerging patterns are likely context dependent. However, these results support the need to maintain natural hydrology and terrestrial life-zones near pools.
Poster Presentation
Student Presentation:
No
Presenting Author:
Thomas Hastings, Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; thomas.hastings@maine.edu
Additional Author(s):
Aram Calhoun Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; calhoun@maine.edu
Malcolm Hunter Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; mhunter@maine.edu
Mitchell Jones, Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; jonemi02@gmail.com
Abstract Body:
Vernal pool breeding species such as wood frogs (Lithobates sylvaticus) have complex life histories that involve annual movements among multiple contiguous, distinct environments. Our objectives were to study wood frog habitat selection and movement after breeding in vernal pools surrounded by human development. We captured and radio-tracked 34 adult wood frogs from mid-April to late-November, replacing lost frogs when necessary. We tracked the movements of 11 frogs leaving the vernal pool during their spring migration. Seven of the 11 frogs moved 183-221 m in a relatively straight line through suburban terrain (streets, lawns, gardens) toward and into a 26 ha forested wetland patch. The mean maximum straight-line distance traveled from the edge of the pool was 169 m. Four frogs in the forested wetland moved shorter distances in unpredictable directions consistent with the behavior observed in studies of wood frogs in undisturbed summer activity areas. Of the six frogs that spent a prolonged time in non-forested environments (6-31 consecutive days), one was killed by a lawn mower, one was trapped in a storm drain, and two settled in a hay field. One other frog was killed by an unknown predator after one day in a lawn. In contrast to studies performed in undisturbed areas, our wood frogs made no fall migration movements and eight selected hibernacula within the forested wetland. Our results demonstrate that wood frogs are capable of moving > 100 m through suburban terrain. However, development surrounding vernal pools may negatively impact wood frog populations via unnatural mortality and restriction of fall migration movements towards vernal pools. This study provides information on the post-breeding habitat of wood frogs that can help
Oral Presentation
Student Presentation:
No
Presenting Author:
Kristine Hoffmann Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; kristine.hoffmann@maine.edu
Additional Author(s):
Aram Calhoun Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; calhoun@maine.edu
Malcolm Hunter Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; mhunter@maine.edu
Abstract Body:
Efforts to conserve wetland communities may be confounded when some animals are far more cryptic than others. For example, Blue-Spotted Salamanders (Ambystoma laterale) and Unisexual Salamanders (A. laterale – jeffersonianum, which reproduce using the sperm of Blue-Spotted Salamanders) are of conservation concern in New England, and are more challenging to detect than Spotted Salamanders (A. maculatum). Therefore, information on wetland use is critical to inform management strategies of these amphibians. Our objectives were to determine which environmental factors affect breeding site use by Blue-Spotted Salamanders, Unisexual Salamanders, and Spotted Salamanders and to examine co-occurrence. We used aquatic funnel traps to survey breeding salamanders at wetlands and modeled site occupancy while accounting for imperfect detection. Detection decreased with days as the breeding season progressed. Blue-Spotted Salamander occupancy was positively related to by vegetation characteristics related to low emergent vegetation cover. Unisexual Salamander occupancy was positively related to counts of captured Blue-Spotted Salamanders, hydric soil within 200 m of the wetland, and vegetation characteristics related to low emergent cover. Spotted Salamander occupancy was positively related to forest cover within 200 m of the wetland, smaller wetland areas, and vegetation characteristics related to canopy closure. These differing relationships imply that management based solely on easily observed species may not lead to conservation of more cryptic salamanders.
Oral Presentation
Student Presentation:
Yes
Presenting Author:
Jared J. Homola, School of Biology and Ecology, University of Maine, Orono, ME 04469; Jared.homola@maine.edu
Additional Author(s):
Michael T. Kinnison Dr., School of Biology and Ecology, University of Maine, Orono, ME 04469; michael.kinnison@umit.maine.edu
Cynthia S. Loftin Dr., U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, Orono, ME 04469; cynthia.loftin@maine.edu
Abstract Body:
Landscape changes that accompany increases in human density (i.e., urbanization) can have detrimental effects on wetland species. For instance, vernal pool amphibians, who undergo seasonal migrations and occasional dispersal among ephemeral wetlands can be expected to experience harmful effects of urbanization when individual movements are inhibited. We paired information on landscape characteristics with microsatellite genetic data from two vernal pool amphibian species to investigate how various natural and anthropogenic landscape features affect connectivity among populations. Egg or larval wood frogs (n = 2439 from 87 sites) and spotted salamanders (n = 2424 from 91 sites) were collected from vernal pools throughout central and southern Maine, U.S.A. Preliminary results suggest that wood frog population structure is strongly influenced by geographic distance between sites (Mantel’s r = 0.381) with genetic divergence increasing nonlinearly between sites of increasing distance. Conversely, relatively strong genetic divergence of spotted salamander populations occurred over much shorter distances, generating an overall weaker relationship to distance (Mantel’s r = 0.068). Decreases in connectivity implied by increases in genetic divergence were evident in the most urbanized study areas. A resistance surface model based on land cover type and various road classes better explained patterns of population structure than distance alone for each species, further supporting an effect of anthropogenic landscape features on interpopulation connectivity. These results will help to inform vernal pool amphibian conservation as human populations continue to grow and concentrate in urban areas.
Oral Presentation
Student Presentation:
Yes
Presenting Author:
Lydia Kifner, Department of Civil and Environmental Engineering, University of Maine, Orono, ME 04469; lydia.kifner@maine.edu
Additional Author(s):
Aria Amirbahman Dr., Department of Civil and Environmental Engineering, University of Maine, Orono, ME 04469; Ariaa@maine.edu
Aram Calhoun Dr., Department of Wildlife, Fisheries, and Conservation Biology, University of Maine, Orono, ME 04469; calhoun@maine.edu
Stephen Norton Dr., School of Earth and Climate Sciences, University of Maine, Orono, ME 04469; Norton@maine.edu
Abstract Body:
Vernal pools are small seasonal wetlands that are crucial for maintaining amphibian and reptile biodiversity in forests in northeastern North America. The pools’ sizes make them especially vulnerable to human disturbances that can have detrimental effects on water quality and other ecosystem functions. As vernal pools are small and ephemeral, they have unique biogeochemical footprints. However, even basic information about their biogeochemical cycles, such as carbon cycling, is largely unknown, which necessitates further research on the subject. Globally, wetlands are significant contributors to greenhouse gas emissions. This study explores the greenhouse gas fluxes from four vernal pools with distinctly different geologic substrates in Maine over a period of four months. Dissolved gas concentrations (CO2, CH4, and N2O) were monitored at the bottom and surface of each pool between April and August 2016 on a weekly basis in order to characterize gas fluxes. N2O concentrations were near detection limits at all locations and times. The aqueous concentrations of CO2 and CH4 ranged from 7.2×10-5 to 2.3×10-3 mol L-1 and 3.9×10-7 to 2.1×10-4 mol L-1, respectively. The concentrations of CO2 and CH4 showed no clear pattern with time. The diffusive fluxes of CO2 and CH4 into the atmosphere ranged from 31 to 498 mmol m-2 d-1, and 0.2 to 72 mmol m-2 d-1, respectively. Fluxes of CO2 generally increased over the period, while fluxes of CH4 showed no clear pattern with time. The masses of CO2 and CH4 dissolved in the vernal pool water and the fluxes from the water to the atmosphere indicate that CO2 and CH4 are being generated in these wetlands. Carbon dynamics and greenhouse gas emissions are crucial to understanding how vernal pools interact with the global atmosphere, and for developing the best management practices to preserve the biogeochemical functions of these ecosystems.
Oral Presentation
Student Presentation:
Yes
Presenting Author:
Kelli M. Straka, School of Earth and Climate Sciences, University of Maine, Orono, ME 04469; kelli.straka@maine.edu
Additional Author(s):
Andrew Reeve Dr., School of Earth and Climate Sciences, University of Maine, Orono, ME 04469; asreeve@maine.edu
Abstract Body:
The effects of global climate change have not been described for vernal pools, ephemeral freshwater wetlands with unique hydrologic characteristics that provide ideal breeding habitat for amphibians. Increased interest in these wetlands has been driven by concern about declining amphibian populations that rely on them, and the realization that they are used by upland species for food, water, and shelter. The hydroperiod of vernal pools, which is affected by climate, dictates the success of the species using the pools. Past studies suggested vernal pool hydrology was driven primarily by precipitation and evapotranspiration. Current research has not quantified, but has indicated groundwater plays a larger role in the hydroperiod than previously suggested. Providing baseline hydrological data will help developers and resource managers make decisions toward better protecting vernal pools. We are creating water budgets for 6 vernal pools in Maine with a focus on quantifying the groundwater component to assess the factors that significantly influence the hydroperiod. Our hydrologic assessment includes volume changes calculated from topography and continuous water level data, shallow hydraulic head piezometer data, and processing of NOAA datasets to calculate evapotranspiration (McGuinness Method) and precipitation rates. Vertical groundwater flow rates and direction were measured using vertical temperature arrays analyzed in a one-dimension heat-transport finite-difference model. The sites with higher hydraulic conductivities had groundwater as a predominant source and loss of water throughout the year, contributing more than 68% of the volume gain and loss. In contrast, pools with lower hydraulic conductivities are precipitation-fed, with precipitation attributing to at least 65% of the volume gain. Evapotranspiration is the dominant pathway of water loss for lower hydraulic conductivity pools from the spring until late summer when the pools are dry. Our research demonstrates that pools with higher hydraulic conductivities can have groundwater as a dominant source and sink for water volume. Understanding the hydrological processes that drive the hydroperiod in vernal pools will provide important information on the effects of climate change and the hydrologic connection with surrounding systems.
About Us
Understanding the vital connections between landowner concerns, municipal planning, conservation activities, and the ecology of vernal pools will be the focus of natural and social scientists from the University of Maine, Boston University, and Bowdoin College as they embark on a multi-year research project concerning Maine’s small natural features—vernal pools.
Our work is supported by: