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G. Jones

Publications and source records attributed to G. Jones.

6 recordsLinked to original sources
USGS2003

Comparing potential fuel treatment trade-off models

Understanding the trade-offs between short-term and long-term consequences of fire impacts on ecosystems is needed before a comprehensive fuels management program can be implemented nationally. We are evaluating 3 potential trade-off models at 8 locations in major U.S. fuel types. We present results of the initial testing of the 3 selected models/modelling approaches and a 4 th model on the Bitterroot National Forest (BNF) in western Montana. The selected models/modelling approaches were 1) the Fire Emissions Trade-off Model (FETM), 2) sequential use of the SIMPPLLE and MAGIS models, 3) the Vegetation Dynamics Development Tool (VDDT), and 4) the LANDscape Succession Model (LANDSUM). We simulated 3 fuel treatments over 50 years: 1) no action, 2) prescribed burning in ponderosa pine and Douglas-fir types at 2 different rates, and 3) timber harvesting that returns the stand to a reproduction stage. Simulation results for all models suggested that the acreage of Douglas-fir and ponderosa pine types would not be appreciably altered by the fuel treatments. Most models suggested the harvest treatment would reduce area burned by wildfire and smoke emissions; some models suggested the prescribed fire treatment would reduce wildfire acreage. All models suggested that the harvest treatment would reduce acreage of pole-size trees; some models suggested the fire treatment would increase acreage of sapling-size trees.

Montana↗
USGS2001

Understanding aquatic animal virus survival and trafficking and its role in risk assessment

The stability of infectious agents in different media and under different physical and chemical environments has been extensively studied for some viruses and virtually ignored for others. Gaps in our knowledge are due in part to difficulties in reproducing virus «life cycles» and determination if the agent is in fact inactive. Additionally, isolation of the agent under certain conditions can present significant challenges. Studies on the susceptibility of viruses to different physical or chemical parameters have often been conducted under artificial conditions and quantitative data on the rate of inactivation are lacking for many agents. Using infectious hematopoietic necrosis virus (IHNV) as an example, survival was assessed under different environmental conditions. Three IHNV isolates that exhibited antigenic and genetic differences were diluted either in freshwater collected from a spring, after it passed through a fish farm, or the river that received water from the fish farm. Each treatment was incubated at 15o C in a water bath and samples were removed daily. Virus concentrations were determined by plaque assay on EPC cells. Virus suspended in spring water survived longer than virus incubated in water obtained from a fish farm or the river. Virus suspended in river water exhibited a 99.99% reduction in virus concentrations in less than 24 h. Survival of IHNV was also evaluated at different temperatures. A 1982 isolate appeared to be less temperature sensitive than isolates collected in 1990. A preliminary study was also conducted to determine the genetic similarity of IHNV isolates present downstream in a river system from the state of Idaho. Isolates were analyzed using the RNase protection assay (RPA) and by nucleotide sequencing of RT-PCR products of specific isolates. Genetic typing of IHNV allows monitoring of virus traffic and may provide insight into the epizootiology and mechanisms of virus spread. These results illustrate the complexity in evaluating virus survival and trafficing and using this sort of information in risk assessment.

Conference Paper↗
USGS1998

Numerical analysis of seawater circulation in carbonate platforms: I. Geothermal convection

Differences in fluid density between cold ocean water and warm ground water can drive the circulation of seawater through carbonate platforms. The circulating water can be the major source of dissolved constituents for diagenetic reactions such as dolomitization. This study was undertaken to investigate the conditions under which such circulation can occur and to determine which factors control both the flux and the patterns of fluid circulation and temperature distribution, given the expected ranges of those factors in nature. Results indicate that the magnitude and distribution of permeability within a carbonate platform are the most important parameters. Depending on the values of horizontal and vertical permeability, heat transport within a platform can occur by one of three mechanisms: conduction, forced convection, or free convection. Depth-dependent relations for porosity and permeability in carbonate platforms suggest circulation may decrease rapidly with depth. The fluid properties of density and viscosity are controlled primarily by their dependency on temperature. The bulk thermal conductivity of the rocks within the platform affects the conductive regime to some extent, especially if evaporite minerals are present within the section. Platform geometry has only a second-order effect on circulation. The relative position of sealevel can create surface conditions that range from exposed (with a fresh-water lens present) to shallow water (with hypersaline conditions created by evaporation in constricted flow conditions) to submerged or drowned (with free surface water circulation), but these boundary conditions and associated ocean temperature profiles have only a second-order effect on fluid circulation. Deep, convective circulation can be caused by horizon tal temperature gradients and can occur even at depths below the ocean bottom. Temperature data from deep holes in the Florida and Bahama platforms suggest that geothermal circulation is actively occurring today to depths as great as several kilometers.

American Journal of Science↗
USGS1996

Spatial scaling of allometry among terrestrial, mammalian carnivores

A regression slope of −0.75 between log 10 density and log 10 body mass is thought to express equivalence of energy conversion among species' populations of similar taxonomic and trophic status. Using larger sample sizes than the usual 1–3 density estimates per species, we estimated a regression slope of −0.71 for terrestrial mammalian carnivores. We investigated the sampling variation in this estimate, and those derived from smaller intra-specific subsets, using 1000-iteration bootstrap analyses to obtain 90% confidence intervals. As expected, these widened as random subsets were reduced in size, but always contained the postulated −0.75. However, log 10 density also declined as 3/4 of the log 10 spatial extent of study area, and study area accounted for virtually all of the variation in density that was previously thought due to body mass. We removed the effect of study area by using the species-specific regression models between density and study area to predict density at a common scale of 400 km 2 . These common-scale densities regressed against body mass with a slope of −0.16, but separated into body mass classes less than and greater than 11 kg, they produced slopes that were not significantly different from zero. We show that the allometry of density could be a case of circular logic, whereby body mass has influenced the investigator's choice of study area, and the resulting scale-dependent densities are related back to body mass. To test the allometry hypothesis, the effect of study area on density estimates needs to be removed. This requires conducting larger-scale studies of the smaller-bodied species so that all species compared are represented by an average study area that is near the common scale. Furthermore, study sites need to be selected and designed to represent more than the local detail in species' density.

Oecologia↗