Cox J.A.,Tall United |
Jones C.D.,University of Georgia
Condor | Year: 2010
Bachman's Sparrow (Peucaea aestivalis) is listed as a species of conservation concern throughout its range and therefore an important candidate for demographic studies. We estimated probabilities of males' annual survival by monitoring a large color-marked population for 4 years by using a combination of (1) mark-resighting within a primary study area and (2) surveys outside the primary area to document emigration. We used multi-strata models to assess probabilities of survival, detection, and movement between the primary study area and the surrounding landscape. In the top models included in our confidence set, probabilities of annual survival were ≥0.68. Probabilities of detection and dispersal varied among the top models but averaged ≥0.86 and ≤0.14, respectively, for individuals in the primary study area. We used a survival probability of 0.68 in combination with published information on the species' productivity to construct a two-stage Leslie matrix. Survival of adult males had the greatest proportional influence on population projections (elasticity = 0.52), while survival of juveniles and annual productivity had equal influence (elasticities = 0.24). Our results suggest that off-plot surveys and multistrata models provide an efficient method for estimating probabilities of survival of Bachman's Sparrow. © 2010 The Cooper Ornithological Society.
Picotte J.J.,U.S. Geological Survey |
Robertson K.,Tall United
Remote Sensing | Year: 2011
Remote sensing using Landsat Thematic Mapper (TM) satellite imagery is increasingly used for mapping wildland fire burned area and burn severity, owing to its frequency of collection, relatively high resolution, and availability free of charge. However, rapid response of vegetation following fire and frequent cloud cover pose challenges to this approach in the southeastern US. We assessed these timing constraints by using a series of Landsat TM images to determine how rapidly the remotely sensed burn scar signature fades following prescribed burns in wet flatwoods and depression swamp community types in the Apalachicola National Forest, Florida, USA during 2006. We used both the Normalized Burn Ratio (NBR) of reflectance bands sensitive to vegetation and exposed soil cover, as well as the change in NBR from before to after fire (dNBR), to estimate burned area. We also determined the average and maximum amount of time following fire required to obtain a cloud-free image for burns in each month of the year, as well as the predicted effect of this time lag on percent accuracy of burn scar estimates. Using both NBR and dNBR, the detectable area decreased linearly 9% per month on average over the first four months following fire. Our findings suggest that the NBR and dNBR methods for monitoring burned area in common southeastern US vegetation community types are limited to an average of 78-90% accuracy among months of the year, with individual burns having values as low as 38%, if restricted to use of Landsat 5 TM imagery. However, the majority of burns can still be mapped at accuracies similar to those in other regions of the US, and access to additional sources of satellite imagery would improve overall accuracy. © 2011 by the authors.
Clewell A.,Tall United
Castanea | Year: 2011
Forest vegetation near Tallahassee, Florida was inventoried on a former cultivated field, called NB66h, which had been abandoned 43 yr earlier. Subsequently, the site suffered no disturbance and no colonization by alien invasive species. The canopy consisted of pines (Pinus taeda, P. echinata) and hardwoods, primarily Liquidambar styraciflua, Quercus nigra. Most tree species were characteristic of plant communities that historically occurred at lower slope positions in the landscape and not of presettlement upland shortleaf pine-oak-hickory woodland. Offsite species colonized surrounding uplands following abandonment of cotton plantations towards the end of the 19th century. Presettlement vegetation was represented by few species and individuals, and offsite species were abundant in every size class. Plant succession was arrested with little sign of directional development towards a predictable seral endpoint. Hypothesized seral trends towards proposed "climax" forests of magnolia-beech and southern mixed hardwoods were not supported. © 2011 Southern Appalachian Botanical Society.
Robertson K.M.,Tall United |
Hmielowski T.L.,Louisiana State University
Oecologia | Year: 2014
Past studies suggest that rates of woody plant resprouting following a "topkilling" disturbance relate to timing of disturbance because of temporal patterns of below-ground carbohydrate storage. Accordingly, we hypothesized that fire-return interval (1 or 2 years) and season of burn (late dormant or early growing season) would influence the change in resprout growth rate from one fire-free interval to the next (Δ growth rate) for broadleaf woody plants in a pine-grassland in Georgia, USA. Resprout growth rate during one fire-free interval strongly predicted growth rate during the following fire-free interval, presumably reflecting root biomass. Length of fire-free interval did not have a significant effect on mean Δ growth rate. Plants burned in the late dormant season (February-March) had a greater positive Δ growth rate than those burned in the early growing season (April-June), consistent with the presumption that root carbohydrates are depleted and thus limiting during spring growth. Plants with resprout growth rates above a certain level had zero or negative Δ growth rates, indicating an equilibrium of maximum resprout size under a given fire-return interval. This equilibrium, as well as relatively reduced resprout growth rate following growing season fires, provide insight into how historic lightning-initiated fires in the early growing season limited woody plant dominance and maintained the herb-dominated structure of pine-grassland communities. Results also indicate tradeoffs between applying prescribed fire at 1- versus 2-year intervals and in the dormant versus growing seasons with the goal of limiting woody vegetation. © 2013 Springer-Verlag Berlin Heidelberg.
Clewell A.F.,Tall United
Castanea | Year: 2013
Shortleaf pine-oak-hickory woodlands provided the principal vegetation cover in the Tallahassee Red Hills prior to land clearing for plantation agriculture in the 19th century. Ample historical documentation and extant remnants of that community, including old-growth, support this conclusion. This woodland was maintained by surface fires and consisted principally of open stands of shortleaf pine, post oak, Spanish oak, black oak, mockernut hickory, and dogwood. The species-diverse and predominantly herbaceous ground cover was dominated by grasses, legumes, and composites. Coppice sprouting of trees and shrubs after fires was common. In the absence of fire, shortleaf pine-oak-hickory woodlands convert to oak-hickory forest with similar tree species composition and loss of herbaceous species. Within the past 130 years, nearly all stands of shortleaf pine-oak-hickory woodlands and oak-hickory forests have been extirpated or compromised beyond recognition by intrusions of offsite tree species that are typical of moist soils at less elevated landscape positions. © 2013 Southern Appalachian Botanical Society.