Geology topics

L.A. Eby

Publications and source records attributed to L.A. Eby.

4 recordsLinked to original sources

USGS2009

Thermal characteristics of amphibian microhabitats in a fire-disturbed landscape

Disturbance has long been a central issue in amphibian conservation, often regarding negative effects of logging or other forest management activities, but some amphibians seem to prefer disturbed habitats. After documenting increased use of recently burned forests by boreal toads (Bufo boreas), we hypothesized that burned habitats provided improved thermal opportunities in terrestrial habitats. We tested this hypothesis by conducting a radio telemetry study of habitat use (reported previously) and by using physical models that simulated the temperature of adult toads. We deployed 108 physical models in and adjacent to a 1-year old burn using a fully-replicated design with three burn severities (unburned, partial, high severity) and four microhabitats (open surface, under vegetation, under log, in burrow). Model temperatures were compared to a range of preferred temperatures in published studies. We found 70% more observations within the preferred temperature range of B. boreas in forests burned with high severity than in unburned areas. Burned forest was warmer than unburned forest across all microhabitats, but the largest relative difference was in burrows, which averaged 3 ??C warmer in high-severity burn areas and remained warmer though the night. More than twice as many observations were within the preferred temperature range in high-severity burrows than in unburned burrows. Areas burned with high severity were still warmer than unburned forest 3 years after the fire. Habitat use of toads during the concurrent radio telemetry study matched that predicted by the physical models. These results suggest there are fitness-linked benefits to toads using burned habitats, such as increased growth, fertility, and possibly disease resistance. However, increased soil temperatures that result from wildfire may be detrimental to other amphibian species that prefer cooler temperatures and stable environments. More broadly, our data illustrate the use of physical models to measure and interpret changes that amphibians may experience from disturbance, and highlight the need for research linking vital rates such as growth and survival to disturbance.

Forest Ecology and Management↗

USGS2008

Post-breeding habitat use by adult Boreal Toads (Bufo boreas) after wildfire in Glacier National Park, USA

Effects of wildfire on amphibians are complex, and some species may benefit from the severe disturbance of stand-replacing fire. Boreal Toads (Bufo boreas boreas) in Glacier National Park, Montana, USA increased in occurrence after fires in 2001 and 2003. We used radio telemetry to track adult B. boreas in a mosaic of terrestrial habitats with different burn severities to better understand factors related to the post-fire pulse in breeding activity. Toads used severely burned habitats more than expected and partially burned habitats less than expected. No toads were relocated in unburned habitat, but little of the study area was unburned and the expected number of observations in unburned habitat was < 3. High vagility of B. boreas and preference for open habitats may predispose this species to exploit recently disturbed landscapes. The long-term consequences of fire suppression likely have had different effects in different parts of the range of B. boreas. More information is needed, particularly in the northern Rocky Mountains, where toads are more likely to occupy habitats that have diverged from historic fire return intervals. Copyright ?? 2008. C. Gregory Guscio. All rights reserved.

Herpetological Conservation and Biology↗

USGS2001

Ecosystem impacts of three sequential hurricanes (Dennis, Floyd, and Irene) on the United States' largest lagoonal estuary, Pamlico Sound, NC

Three sequential hurricanes, Dennis, Floyd, and Irene, affected coastal North Carolina in September and October 1999. These hurricanes inundated the region with up to 1 m of rainfall, causing 50- to 500-year flooding in the watershed of the Pamlico Sound, the largest lagoonal estuary in the United States and a key West Atlantic fisheries nursery. We investigated the ecosystem-level impacts on and responses of the Sound to the floodwater discharge. Floodwaters displaced three-fourths of the volume of the Sound, depressed salinity by a similar amount, and delivered at least half of the typical annual nitrogen load to this nitrogen-sensitive ecosystem. Organic carbon concentrations in floodwaters entering Pamlico Sound via a major tributary (the Neuse River Estuary) were at least 2-fold higher than concentrations under prefloodwater conditions. A cascading set of physical, chemical, and ecological impacts followed, including strong vertical stratification, bottom water hypoxia, a sustained increase in algal biomass, displacement of many marine organisms, and a rise in fish disease. Because of the Sound's long residence time (???1 year), we hypothesize that the effects of the short-term nutrient enrichment could prove to be multiannual. A predicted increase in the frequency of hurricane activity over the next few decades may cause longer-term biogeochemical and trophic changes in this and other estuarine and coastal habitats.

Proceedings of the National Academy of Sciences of↗

USGS1997

Modeling changes in growth and diet on polychlorinated biphenyl bioaccumulation in Coregonus hoyi

Restrictions on the release of PCBs into the environment began in the early 1970s, resulting in reduced PCB concentrations in Lake Michigan bloaters ( Coregonus hoyi ). However, since 1980, PCB concentrations in bloater have declined only slightly. The bloater population also increased 40-fold during 1970 through 1984, resulting in a diet shift and a density-dependent decline in growth. Our goal was to determine how these changes in diet and growth may have affected PCB accumulation in Lake Michigan bloater. We evaluated the consequences of these two changes on bloater PCB concentrations by developing a bioenergetics-based PCB bioaccumulation model. Bloater PCB concentrations increased little when we increased the amount of Diporeia hoyi, the most contaminated prey, in the bloater diet. By comparing constant growth (similar to those of the 1970s) to observed decline in growth rates, we found that lower growth rates during the 1980s placed older, more contaminated bloaters in the size range most vulnerable to predators and in the size range sampled by PCB monitoring programs. Bloater PCB concentration trends may be influenced by the sampling methodology of the United States Geological Survey. If fish PCB trends are to be used as an indicator of system-level PCB trends, sampling should include a representative sample of fish of known age from the population.

Ecological Applications↗