Geology topics

D.A. Kovacic

Publications and source records attributed to D.A. Kovacic.

5 recordsLinked to original sources

USGS2008

Ant community composition across a gradient of disturbed military landscapes at Fort Benning, Georgia

Military training, soil texture, and ground cover influence ant communities at Fort Benning, a military installation in west-central Georgia. We sampled 81,237 ground-dwelling ants (47 species in 20 genera) with pitfall traps at 40 sites on a continuum from nearly pristine forest to highly disturbed training areas. We also measured 15 environmental variables related to vegetation and soil. Sites disturbed by military training had fewer trees, less canopy cover, more bare ground, and more compact soils with shallower A-horizons than comparable undisturbed sites. Pheidole bicarinata, Dorymyrmex smithi, and Pogonomyrmex badius dominated the most highly disturbed sites. Competitively submissive myrmicines, such as Aphaenogaster and Crematogaster, and formicines, such as Camponotus and Formica, were abundant in the undisturbed sites. Solenopsis invicta occurred in all but the least disturbed sites. Ant community composition was a useful indicator of disturbance at Fort Benning.

Southeastern Naturalist↗

USGS2005

Leaf fluctuating asymmetry, soil disturbance and plant stress: A multiple year comparison using two herbs, Ipomoea pandurata and Cnidoscolus stimulosus

We studied Cnidoscolus stimulosus and Ipomoea pandurata, two common herbs of the Fall Line Sandhills to assess their potential as ecosystem level stress indicators. We focused on plants because they are among the most persistent organisms in terrestrial ecosystems. We used developmental instability as an indicator of plant population stress. Developmental instability is usually measured as deviations from symmetry, in traits that normally develop symmetrically. Thus, symmetry represents an idealized a priori phenotype. Stress presumably causes perturbations during development that may exceed the capacity of the organism to buffer or correct, resulting in developmental instability, and hence deviations from this ideal. Soil disturbance imposed by different land use patterns at Fort Benning, Georgia provided a gradient of soil disturbance. In 2000-2002 we collected plants from nine different sites representing three levels of disturbance. In addition, in 2002 we collected microhabitat data in 1 m quadrats surrounding each plant whose developmental stability we also assessed. The developmental instability of both species was influenced by land use patterns, whether or not the sites had been previously burned, and microhabitat variables. Developmental instability increased with soil disturbance, burning in the prior year, and as the percentage of bare ground increased around the target individual. To some extent, favorable microhabitat conditions reduced developmental instability in sites with medium and high soil disturbance, whereas unfavorable conditions at low soil disturbance sites increased developmental instability. As an indicator of community level stress, developmental instability is best used in conjunction with other indices of environmental quality. ?? Published by Elsevier Ltd.

Ecological Indicators↗

USGS2005

Development of ecological indicator guilds for land management

Agency land-use must be efficiently and cost-effectively monitored to assess conditions and trends in ecosystem processes and natural resources relevant to mission requirements and legal mandates. Ecological Indicators represent important land management tools for tracking ecological changes and preventing irreversible environmental damage in disturbed landscapes. The overall objective of the research was to develop both individual and integrated sets (i.e., statistically derived guilds) of Ecological Indicators to: quantify habitat conditions and trends, track and monitor ecological changes, provide early warning or threshold detection, and provide guidance for land managers. The derivation of Ecological Indicators was based on statistical criteria, ecosystem relevance, reliability and robustness, economy and ease of use for land managers, multi-scale performance, and stress response criteria. The basis for the development of statistically based Ecological Indicators was the identification of ecosystem metrics that analytically tracked a landscape disturbance gradient.

Report↗

USGS2004

Estimating disturbance effects from military training using developmental instability and physiological measures of plant stress

We used developmental instability, water potential, and variable fluorescence to determine if populations of winged sumac (Rhus copallinum) were being negatively effected by military training disturbance. We established nine sites that represented a land-use disturbance gradient with three impact levels (low, medium, and high), the effects mostly due to mechanized infantry training maneuvers. Although mean values of developmental instability, water potential, and variable fluorescence differed significantly among sites, the patterns did not consistently differentiate sites relative to the disturbance gradient. At the population level, some measures of developmental instability and variable fluorescence were positively correlated. All nine sites consisted of habitat mosaics, with the abundance of higher quality habitat patches and canopy gaps closely related to habitat impacts. It may be that R. copallinum is selecting similar micro-environments at all sites and therefore minimizing inter-site variation in stress measures, despite large differences in overall habitat condition. Our results call for caution in developing ecological indicators using the response of physiological and morphological measures from a single plant species. ?? 2003 Elsevier Ltd. All rights reserved.

Ecological Indicators↗

USGS2004

Habitat disturbance and the diversity and abundance of ants (Formicidae) in the Southeastern Fall-Line Sandhills

We examined habitat disturbance, species richness, equitability, and abundance of ants in the Fall-Line Sandhills, at Fort Benning, Georgia. We collected ants with pitfall traps, sweep nets, and by searching tree trunks. Disturbed areas were used for military training; tracked and wheeled vehicles damaged vegetation and soils. Highly disturbed sites had fewer trees, diminished ground cover, warmer soils in the summer, and more compacted soils with a shallower A-horizon. We collected 48 species of ants, in 23 genera (141,468 individuals), over four years of sampling. Highly disturbed areas had fewer species, and greater numbers of ants than did moderately or lightly disturbed areas. The ant communities in disturbed areas were also less equitable, and were dominated by Dorymyrmex smithi .

Georgia↗