Directorate of Public Works

Honolulu, HI, United States

Directorate of Public Works

Honolulu, HI, United States
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Fill J.M.,University of South Carolina | Fill J.M.,Stellenbosch University | Moule B.M.,Directorate of Public Works | Varner J.M.,Virginia Polytechnic Institute and State University | And 2 more authors.
Plant Ecology | Year: 2016

Understanding the flammability of species in fire-prone or fire-dependent ecosystems is necessary for modeling and predicting ecosystem dynamics. Wiregrass (Aristida stricta syn. A. beyrichiana), a keystone perennial bunchgrass, is a dominant groundcover species in southeastern United States pine savannas. Although wiregrass flammability as a driver of pine savanna fire regimes is a fundamental paradigm in pine savanna dynamics, no studies have quantified its fuel structure and flammability at the individual bunchgrass level. We studied wiregrass flammability at the Aiken Gopher Tortoise Heritage Preserve in Aiken County, South Carolina, USA. We linked tussock fuel structure characteristics (total biomass, live:dead biomass, mass of perched litter and pine needles, moisture content, and bulk density) to flammability (flaming duration, smoldering duration, and flame length). Flame length was strongly and positively related to wiregrass biomass. Pine needles and other litter fuels perched on wiregrass tussocks were not related to flame length, but increased the duration of flaming and smoldering. Within the ranges evaluated, neither fire weather (relative humidity, wind speed, and air temperature) nor fuel moisture significantly affected tussock flammability. Our results indicate that different fuel structural properties drive separate aspects of wiregrass flammability. Together with litter from pines and other groundcover shrubs and trees, wiregrass modifies fire behavior locally, potentially influencing ecosystem dynamics at larger scales. These results have strong implications for southeastern pine savannas and more broadly where grass-dominated vegetation influences fire regimes. © 2016 Springer Science+Business Media Dordrecht

Munson S.M.,U.S. Geological Survey | Webb R.H.,University of Arizona | Housman D.C.,Directorate of Public Works | Veblen K.E.,Utah State University | And 7 more authors.
Journal of Ecology | Year: 2015

Recent elevated temperatures and prolonged droughts in many already water-limited regions throughout the world, including the southwestern United States, are likely to intensify according to future climate-model projections. This warming and drying can negatively affect perennial vegetation and lead to the degradation of ecosystem properties. To better understand these detrimental effects, we formulate a conceptual model of dryland ecosystem vulnerability to climate change that integrates hypotheses on how plant species will respond to increases in temperature and drought, including how plant responses to climate are modified by landscape, soil and plant attributes that are integral to water availability and use. We test the model through a synthesis of fifty years of repeat measurements of perennial plant species cover in large permanent plots across the Mojave Desert, one of the most water-limited ecosystems in North America. Plant species ranged in their sensitivity to precipitation in different seasons, capacity to increase in cover with high precipitation and resistance to decrease in cover with low precipitation. Our model successfully explains how plant responses to climate are modified by biophysical attributes in the Mojave Desert. For example, deep-rooted plants were not as vulnerable to drought on soils that allowed for deep-water percolation, whereas shallow-rooted plants were better buffered from drought on soils that promoted water retention near the surface. Synthesis. Our results emphasize the importance of understanding climate-vegetation relationships in the context of biophysical attributes that influence water availability and provide an important forecast of climate-change effects, including plant mortality and land degradation in dryland regions throughout the world. © 2015 British Ecological Society This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Floyd R.H.,Colorado State University | Ferrazzano S.,Oak Ridge Institute for Science and Education | Josey B.W.,Oak Ridge Institute for Science and Education | Applegate J.R.,Directorate of Public Works
Castanea | Year: 2015

Aldrovanda vesiculosa L., a free-floating aquatic carnivorous plant native to the Old World, has been documented from several ponds and connecting wetlands at U.S. Army Garrison, Fort A.P. Hill in Caroline County, Virginia. This species is believed to have been introduced from a nearby cultivated population, and has spread rapidly throughout many of Fort A.P. Hill's acidic wetlands, which is surprising given Aldrovanda's extreme rarity in its native Old World habitats. The unusual biological vigor of this species at Fort A.P. Hill warrants closer attention from the regional scientific community because very little is known about this species' behavior in North America, the effects on local trophic dynamics, and its short- and long-term interactions with native species. With limited information available, it is difficult to predict to what extent Aldrovanda will influence the natural ecosystem and how this species should be managed. One of Fort A.P. Hill's early objectives is to raise regional awareness of this species, and provide early documentation of Aldrovanda within central Virginia. © Copyright 2015 Southern Appalachian Botanical Society.

Holland B.S.,Pacific Biosciences | Montgomery S.L.,Associate in Natural science | Costello V.,Directorate of Public Works
Biodiversity and Conservation | Year: 2010

Here we report the first conclusive evidence of an introduced reptile (Chamaeleo jacksonii) feeding on Hawaiian taxa, including 11 snails in four endemic genera from two families, including four individuals of an endangered species (Achatinella mustelina), and native insects in five genera. Native Hawaiian invertebrates were discovered in the dissected stomachs of wild caught Jackson's chameleons collected from June to November 2009 on the island of Oahu. Although Jackson's chameleons were introduced to the Hawaiian Islands in the early 1970s, ecological impacts have never been documented. Of particular concern is the fact that chameleons have previously only rarely been found in native Hawaiian habitat, although 12 were recently collected in a mid-elevation native forest, an area that is not likely to be suitable for their long-term persistence, but that is adjacent to higher elevation pristine forest where endemic prey are abundant and favorable climatic conditions exist for chameleon persistence. One concern is that Jacksons's chameleons may be undergoing a range expansion into upper elevation pristine forests. If chameleons reach and establish populations in these areas, devastating impacts to the native ecosystem are possible. A thorough understanding of the impacts of chameleons on Hawaiian fauna will require additional evaluation and sampling, but dissemination of this discovery in a timely fashion is important as it provides new information regarding this threat. Monitoring and collection of chameleons is ongoing, particularly in native Hawaiian forest habitats at mid and upper elevations (600-1,300 m). © Springer Science+Business Media B.V. 2009.

Wrobel J.,Directorate of Public Works | Gross J.P.,Weston Solutions
Military Engineer | Year: 2010

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), or Superfund, remedial action of a 15-acre former salvage yard, fire training area and disposal area at Aberdeen Proving Ground (APG), demonstrates a successful integration of waste reduction and traditional environmental remediation. The site, known as the G-Street Salvage Yard, was on the Superfund National Priorities List for industrial surface and sub-surface soil contamination as well as complications of potential munitions and explosives of concern and chemical warfare material. An important goal of the remediation effort was to minimize the quantity of contaminated media disposed, and to increase the diversion of solid waste as appropriate in a cost-effective manner. Waste reduction techniques include incremental excavation using 12-in lifts where chemical contamination was present at shallow depths, surgical excavation to minimize the number of trees removed, segregation of recyclable metals, a result of the historical use of the site, from excavation waste.

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