Seasonal variation in water sources of the riparian tree species Acer negundo and Betula nigra in the southern Appalachian foothills, USA
Determining which water sources a plant accesses throughout an entire year is an important step in understanding how changes in source characteristics, such as water availability and quality, affect utilization by a plant. The current study examined the primary water sources of selected riparian species common in the foothills of the southern Appalachians, Acer negundo and Betula nigra, during the phenological stages of spring leaf bolt, flowering, and leaf senescence/abscission. Source utilization was monitored monthly by comparing the stable isotopic composition of water samples taken from woody tissue to those collected from possible water sources. Throughout the year, both species used a combination of deep ground and shallow soil water sources, with a greater reliance on deeper sources during the late growing season. Water extracted from B. nigra was typically more depleted in δ2H than all collected sources, while values from A. negundo were more variable throughout the study period. Intraspecifically, isotopic values did not vary on a monthly or seasonal scale for either species (P>0.56), while interspecific values were different only at December, January, and July samplings (P<0.02). Strong positive relationships between air temperature and isotopic values of both species (P<0.04) were also found and may be due to increased evaporation of moisture from the upper soil layers, which both species appeared to use most of the year.
Dept of Biology, Wake Forest University, Winston-Salem, NC
Using Optimal Foraging Theory to Assess the Conservation Value of Managed Ecosystems
With the United States’ growing population, an increasing need for farmland has led to the destruction of native prairies. These prairies act as a breeding and foraging environment for migratory birds, including the Bell’s Vireo (Vireo belli). Because large-scale prairie preserves are not economical, it is essential to determine what factors are necessary to optimize foraging abilities of nesting birds while minimalizing the space needed. Optimal foraging theory suggests that nests surrounded by native vegetation would be less susceptible to predation or the environment because the adults would spend more time on the nest and less time foraging, leaving them fed and able to protect their young. In order to accomplish this, over two years Bell’s Vireo nests were identified on both prairies and farmland and movements were film during egg laying and fledging periods. In particular we filmed time adults spent away from the nest. By collecting data on the surrounding landscape and analyzing video to determine how much time adults spent on each nest how the type of surrounding vegetation correlates to foraging efficiency. Preliminary analysis suggests that more time was spent away from the nest when embedded in native grasslands. These data suggest that conservation of the Bell’s Vireo may be effective in managed ecosystems.
119 • Thomas A. Maigret1, John J. Cox1, Dylan R. Schneider2, Christopher D. Barton1, Steven J. Price1, Jeffrey L. Larkin2
Effects of Timber Harvest Within Streamside Management Zones on Salamander Populations in Ephemeral Streams of Southeastern Kentucky
Habitat loss and fragmentation are two of the most important causes of global population declines and extinction of amphibians. Forestry is an important extractive, economic activity to many human economies, but it can be detrimental to ecosystem function and species viability therein. Salamanders comprise a significant amount of forest community biomass, and given their sensitivity to environmental stressors, often serve as important indicators of declines in forest ecosystem function. Several studies have focused on the impacts of timber harvest on salamanders inhabiting perennial streams, the findings of which have helped inform timber best management practices in the U.S. Headwater streams and associated riparia account for a small fraction of the total landscape, yet these features are critical to the functioning of forested ecosystems; however, few have examined how timber harvest impacts salamanders in or near these areas. Our objective was to investigate the effects of three different silvicultural treatments, each involving different streamside management zone (SMZ) characteristics, on salamander communities in ephemeral streams. Data were collected by regular checks of pitfall traps, coverboards, and transect searches. Using both pre- and post-harvest data, abundance estimates were acquired using binomial mixture models. Declines in some species of terrestrial and stream-breeding salamanders were detected, and were shown to be likely related to characteristics of the corresponding silvicultural treatment. We suggest that application of modest SMZ regulations to ephemeral streams would likely reduce or eliminate alleviate salamander declines in these important headwater areas.
1 Dept of Forestry, University of Kentucky, Lexington, KY; 2 Dept of Biology, Indiana University of Pennsylvania, Indiana, PA
120 • Meaghan L. Fabrycki, David Vandermast
Patterns of Tree Mortality and Replacement on Elon University Forest
Forests of continuity (FOC) are underappreciated and poorly recognized resources in successional landscapes. An earlier study described 6 ha of forest within the boundaries of a 22.5 ha old farmstead that is now Elon University Forest (EUF), with the compositional and structural characteristics of a forest that appears to have never been clearcut. The trees in this patch of forest are common late-successional species, are large and old for their species, and tip-mound depressions and standing dead trees indicate that succession here is dominated by gap-dynamics rather than response to historical clearcutting. To further our understanding of FOC, this study compares sapling (stems >1.4m tall and <10 cm dbh) composition and structure between the FOC and the earlier successional forests surrounding it on EUF. Our results indicate that the FOC has a significantly different sapling population than forests recovering from clearcutting. In particular, the FOC has more saplings (3295/ha vs. 1838/ha, p=0.036) that are more likely to be shade-tolerant, late-successional species such as mockernut hickory (Carya alba) and white oak (Quercus alba) than the younger forest. In contrast, the younger forest had far more yellow-poplar (Liriodendron tulipifera) and red maple (Acer rubrum). FOC also had higher diversity, more sapling species and lower evenness than did the younger forest. NMS ordination and cluster analysis on sapling composition grouped plots in the FOC as distinct from the younger forest plots.
