Browsing by Author "Kenneth H. Pollock, Member"

Now showing 1 - 5 of 5

Assessing 100-meter-wide loblolly pine corridors as breeding habitat for landbirds
(2002-01-16) Amacher, Andrew James; Richard A. Lancia, Chair; Jamie Collazo, Member; Kenneth H. Pollock, Member
I evaluated the suitability of 100-meter-wide loblolly pine (Pinus taeda) plantation corridors as breeding habitat for landbirds. The study was located within the Lower Coastal Plain of South Carolina on land owned by Westvaco Timber Corporation. The typical rotation-age within the landscape was 20 years. Work was conducted within post-rotation-age (24-31 years) corridors (100-meter-wide linear loblolly pine plantation stands) and patches (typical Westvaco stands). Work was also conducted in rotation-age patches (18-22 years). Vegetation, point count and nest monitoring data were used to compare corridors against patches. Point count surveys were conducted from 1995-1999, and vegetation and nest surveys from 1997-2000. Vegetation data was collected between 1997-2000 within post-rotation-age corridors and patches (24-31 years) and rotation-age patches (18-22 years). I used 10th acre plots to quantify the following variables: pine, hardwood, and snag basal area; pine, hardwood, and snag dbh; canopy cover (%) and shrub cover; overstory and midstory height; and cane and vine cover. Cluster analysis of individual plots found that post-rotation-age corridors and patches were not significantly different (p = 0.1178) from each other, but were significantly different from rotation-age stands (p < 0.0001). Individual comparisons between classifications (post-rotation corridors and patches, rotation-age patches) found most significant differences between post-rotation-age and rotation-age stands. However, post-rotation-age corridors and patches differed significantly in pine basal area (p < 0.0001), pine DBH (p < 0.0001), hardwood basal area (p = 0.0153) and shrub percent cover (p = 0.0358). Point count data was collected from 1996-1999 within post-rotation-age corridors and patches. A total of 94 corridor points and 116 patch points were surveyed from 1996-1999. Corridors had greater species richness (N=44) than patches (N =38). However, species composition was similar between corridors and patches. For all species, the Spearmans rho correlation coefficient on species ranked abundance was highly correlated (r = 0.7877, p <0.0001). In individual species comparisons, only the Red-eyed Vireo was found in lower abundance within corridors (0.213 birds/plot) compared to patches (0.440 birds/plot, p =0.0011). The Brown-headed Cowbird and Blue-gray Gnatcatcher were significantly more abundant within corridors relative to patches. Nest searching was conducted within post-rotation-age corridors and patches, and rotation-age patches from 1997-2000. Three species were compared: the Acadian Flycatcher (n = 132), Hooded Warbler (n = 37), and Northern Cardinal (n = 52). Across all years, no significant difference in nest survival was found between nests within post-rotation-age corridors and nests within post-rotation-age patches for all 3 species. However, when compared to rotation-age patches, Acadian Flycatchers had significantly higher nest survival in both post-rotation-age corridors and patches (p < 0.05). Hooded Warblers had marginally higher nest success in both post-rotation-age corridors and patches relative to rotation-age patches (p = 0.05-0.10). Nest survival was also compared by distance to edge (with loblolly stands aged 0-5 years), distance to road, and distance to edge+road. No significant differences were found in nest survival for the Acadian Flycatcher, Hooded Warbler, and Northern Cardinal based on a nest's distance to edge, road, or road+edge. The Hooded Warbler had 10 out of 37 nests (27%) parasitized by the Brown-headed Cowbird. Nine were within patches and 1 within a corridor. Parasitzed nests were not significantly different from non-parasitized nests based on distance to edge (p = 0.7100), distance to road (p = 0.2111), or distance to edge+road (p= 0.2492).
Distribution of Breeding Birds in Great Smoky Mountains National Park
(2002-01-22) Shriner, Susan Ann; Theodore R. Simons, Chair; Jaime A. Collazo, Member; Martha J. Groom, Member; Scott M. Pearson, Member; Kenneth H. Pollock, Member
We assessed the utility of developing predictive models of species distribution within a large contiguous forest based solely on GIS (Geographic Information Systems) data. We conducted more than 7000 point count surveys of breeding birds at approximately 4000 locations throughout Great Smoky Mountains National Park (GSMNP). We combined these empirical data with habitat, topographic, and location variables to develop logistic regression models for 20 breeding bird species. The mean of observed points correctly classified for evaluation data was 74.3% with a range of 67.4% to 83.1%. Mean improvement in model classification rates with the addition of a trend surface was 0.9% with a range of -0.4% to 2.0%. We also assessed the importance of controlling for differences in species detectability in different vegetation types. Comparisons of models based on unlimited radius plot data with models based on fixed width plot data that minimized detectability differences between vegetation types showed classification rates dropped an average of 0.9% with a range of -3.8% to 3.7% for fixed width plots. In the eastern U.S., invasion of hemlock wooly adelgid (Homoptera: Adelgidae: Adelges tsugae) is transforming species composition of native forests by causing extensive mortality in eastern hemlock (Tsuga canadensis) populations. We assessed the potential effects of hemlock loss in GSMNP by evaluating current hemlock distribution and abundance patterns and identifying environmental correlates of hemlock presence. We investigated potential effects of hemlock mortality on the park's avifauna by identifying bird species associated with hemlock. Our results indicate hemlock is widespread in all vegetation strata at low and mid elevations and is the second most common tree species in the park. Hemlock presence is significantly associated with elevation, total relative moisture index, disturbance history, vegetation type, and bedrock geology. Sixteen of 30 common breeding bird species showed significant correlations with hemlock presence. Hemlock loss will favor increased abundance of avian species associated with early successional and disturbed habitats and reduced abundance of avian species associated with late successional forests.We compared breeding bird community structure and composition in old growth and mature second growth (65-100 years old) forests in the southern Appalachians using paired point count. We found few differences in the two communities. Comparisons of relative abundance based on counts of individual bird species showed two species were significantly more abundant on old growth sites and one species was significantly more abundant on second growth sites. After incorporating differential detectability into relative abundance estimates, we found that 4 breeding bird species were significantly more abundant in old growth sites compared to second growth sites and that no breeding bird species was significantly more abundant in second growth sites. These results highlight the importance of incorporating detectability measures into sampling and analytic methods. Analysis of vegetation samples for the paired sites showed significant differences between old growth and second growth sites. Old growth sites had significantly more large trees for classes > 50 cm diameter at breast height. Vegetation composition comparisons showed old growth sites had significantly more late successional species and significantly fewer species associated with early successional forests. Nonetheless, measures of species richness, relative abundance, and number of standing snags did not differ between old growth and second growth sites. Breeding bird composition similarities between old growth and second growth sites in this study may not be typical of more fragmented landscapes because large remaining patches of old growth forest adjacent to second growth sites may ameliorate differences between the two habitats.
Landscape effects on breeding songbird abundance in managed southern Appalachian forests
(2000-10-16) Lichstein, Jeremy William; Theodore R. Simons, Chair; Kenneth H. Pollock, Member; George R. Hess, Member; Kathleen E. Franzreb, Member
Many studies have demonstrated adverse effects of forest fragmentation on breeding forest songbirds in North America, and the viability of regional populations is thought to depend on large, unfragmented forests. However, we know relatively little about the landscape scale consequences of management in the forested landscapes that are presumed to be important to maintaining songbird metapopulations. The southern Appalachians, a mostly forested region, contains the largest network of public lands in the eastern U.S. Most of these public lands are managed by the U.S. Forest Service. To begin to understand the landscape scale effects of forest management in the southern Appalachians, I examined the relationship between the relative abundance of different species of breeding songbirds and local and landscape scale habitat variables in two predominately mid- to late-successional National Forests in the southern Appalachian Mountains, USA: the French Broad Ranger District of Pisgah National Forest (North Carolina) and the Nolichucky Ranger District of Cherokee National Forest (Tennessee). As part of the study, I explored two statistical problems frequently encountered in species-environment analysis: count data and spatial autocorrelation. Results from classical normal-errors regression models were similar to results from Poisson and negative binomial models that explicitly model counts. Normal-errors regression models were then modified to account for spatial autocorrelation using a conditional gaussian autoregressive model. Most species, especially Neotropical migrants, were significantly correlated with at least one landscape variable. These correlations included both landscape composition (i.e., the proportion of different landcover types) and landscape pattern (i.e., the spatial arrangement of landcover types) variables at 500 m to 2 km landscape scales. However, these landscape effects explained only a small fraction of the variation in bird relative abundance, and most species appear to respond primarily to elevation and local habitat factors in my study area. My results are consistent with other studies that have reported only weak to moderate landscape effects on songbird abundance in large managed forests. These results should not be interpreted as being inconsistent with results from studies in highly fragmented forests that have reported strong effects of patch size, patch isolation, and landscape scale forest cover on breeding songbirds.
Population Dynamics of Largemouth Bass in Lucchetti Reservoir, Puerto Rico
(2002-01-02) Ozen, Ozcan; Richard L. Noble, Chair; Kenneth H. Pollock, Member; James A. Rice, Member; Joseph E. Hightower, Member
Juvenile largemouth bass C annually. Water level increase could be used to stimulate largemouth bass spawning in systems where water temperature is suitable. CPUE of age-1 largemouth bass was positively correlated with water levels of the previous year and negatively correlated with water level fluctuations. The effect of these hydrological variables on largemouth bass recruitment appeared to be exponential rather than linear. Age-1 largemouth bass comprise the majority of the fishable stock in Lucchetti Reservoir, and the stock is typically below carrying capacity. Thus, the potential exists to adopt a water level management plan during the spawning period of largemouth bass to ensure successful largemouth bass recruitment into the next year's fishable stock.
Responses of Prey to the Presence of Predators in a Fragmented Landscape with Corridors
(2002-04-12) Brinkerhoff, Robert Jory; Nick M. Haddad, Chair; James F. Gilliam, Member; Kenneth H. Pollock, Member
Corridors have been shown to serve as movement conduits for a wide variety of species, though their effects on interspecific interactions have been largely unstudied. I designed a replicated experiment to investigate corridor-mediated prey responses to predators in a network of open habitat patches surrounded by a matrix of planted pine forest. I used mark-recapture studies and foraging trays to monitor the movements and behaviors of several small mammal species. The presence of predators was artificially manipulated in half of my replicates by applying bobcat urine to specific patches. I then compared the movements of small mammals and changes in foraging activity in the treated and untreated replicates, and tested how corridors affected behaviors and population sizes. I found significant differences in foraging activity between patches treated with predator urine and patches to which they were connected, whereas I found no differences in foraging activity in unconnected patches adjacent to treated patches. Movements detected by mark-recapture were too infrequent for analysis, but were proportionally consistent with previous results showing corridor effects on movement. There were no significant differences in small mammal abundances between connected and unconnected patches. These results suggest that corridors do facilitate movement between habitat patches and prey will preferentially use corridors to forage in patches with reduced predation risk. However, the corridors in this study had no apparent affect on long-term displacement of small mammals.