A Data-Based Conservation Planning Tool for Florida Panthers

Habitat loss and fragmentation are the greatest threats to the endangered Florida panther (Puma concolor coryi). We developed a data-based habitat model and user-friendly interface so that land managers can objectively evaluate Florida panther habitat. We used a geographic information system (GIS) and the Mahalanobis distance statistic (D ²) to develop a model based on broad-scale landscape characteristics associated with panther home ranges. Variables in our model were Euclidean distance to natural land cover, road density, distance to major roads, human density, amount of natural land cover, amount of semi-natural land cover, amount of permanent or semi-permanent flooded area–open water, and a cost–distance variable. We then developed a Florida Panther Habitat Estimator tool, which automates and replicates the GIS processes used to apply the statistical habitat model. The estimator can be used by persons with moderate GIS skills to quantify effects of land-use changes on panther habitat at local and landscape scales. Example applications of the tool are presented.     

Natural organic compounds as alternative to methyl bromide for nematodes control

Thirty-three organic acids and furfural metabolites were examined for their nematicidal activity against plant-parasitic, free-living and predacious nematodes. Propionic acid, 2-methylhexanoic acid, lactic acid, maleic acid, and furic acid were the most effective nematicides among normal chain organic acids, branched organic acids, hydroxy/keto-acids, dicarboxylic acids and furfural metabolites, respectively. Seven of the tested compounds were found to have more than 90% mortality thus designating them as highly active nematicides. Of the highly active tested compounds, an average octanol/water log P of 0.97 was observed with a range from 0.28 to 2.64, and a Henry's Law constant averaging 2.6 × 10^{? 7} atm.m³/mole. Tested chemicals with minor or low nematicidal activity showed an average log P of 1.76 with a range from 0.15 to 3.42 and a Henry's Law constant averaging 16.6 × 10^{? 7} atm.m³/mole.     

Influx,transport, and accumulation of cadmium in plant species grown at different Cd2+ activities

Abstract

Cadmium (Cd) has no known essential biological function, but it is toxic to plants, animals, and humans. A promising approach to prevent Cd from entering the food chain would be to select and/or create Cd‐accumulating plants to remediate contaminated soils or to develop Cd‐excluding plants to reduce Cd flow from soils into foods. The present study was undertaken to examine the differences in Cd influx, transport, and accumulation among five plant species in relation to plant tolerance to Cd toxicity. Ryegrass (Lolium perenne L.) had the least reduction in dry matter which may be due to its lowest Cd transport rate (TR) to shoots at all Cd levels among the plant species tested. White‐clover (Trifolium repens L.) was the most sensitive species to Cd toxicity, likely because of its highest Cd influx rate (IR) and high TR when plants were grown at low Cd²⁺ activity (≤8 μM). The high tolerance of cabbage (Brassica oleracea var. capitata L.) to moderate Cd toxicity (≤14 μM) appeared to be mainly due to the detoxification of Cd inside plant tissue since it recorded the highest TR and relatively high IR for Cd among the tested species. At Cd²⁺ activities up to 28 uM, the Cd uptake ratios of shoot/root for ryegrass were, on average, about 50‐fold and 27‐fold lower than that for cabbage and maize (Zea mays L.), respectively. These results showed that Cd could be easily transported into shoots of cabbage and maize, but was mainly confined to roots of ryegrass. We suggest that influx and transport rates, especially transport rate, could be used as plant physiological parameters for screening Cd‐excluding genotypes among monocotyledonous plants.     

summary of the California aerosol characterization experiment

This report gives a brief summary of the experimental plan and the early results of field observations from the California Aerosol Characterization Experiment (ACHEX). The objectives of the program center on questions of the sources and evolution of aerosols in urban air, as they are superimposed on a natural background, particularly as they relate to visibilitydegradation. The project initially nvolved the use of an elaborately instrumented mobile laboratory combined with a fixed station in San Jose, in Pasadena, and in Riverside, and later incorporated several satellite monitoring stations in the Los Angeles Basin. Intensive field observationswere taken from July 1972 to November 1972 in several urban and nonurban locations between the San Francisco Bay area and the South Coast Basin, covering the Los Angeles area. In a second phase of the ACHEX, aerosols accompanying photochemical smog were studied intensively in the Los Angeles Basin during the period between July and October of 1973. The observations cover a wide variety of parameters including physical and chemical properties of aerosols, pollutant gas concentrations, and meteorological variables. The initial results show the great importance of sulfate, nitrate, noncarbonate carbon, and liquid water to the mass concentration of airborne particles and their relation to reduction in visibility. The anthropogenic contribution to atmospheric aerosols is consistently found to be allocated primarily to the submicron or fine particle size range.     

Valuing nature-based recreation in public natural areas of the Apalachicola River region, Florida

As more people visit natural areas for tourism and recreation purposes, it is becoming increasingly important to understand the value they place on these natural resources. Specifically, tourists to Florida have been increasingly interested in visiting natural areas, forests, parks, and preserves-highlighting the importance of this new and growing phenomenon. We analyze visitors' demand for nature-based recreation in the Apalachicola River region of Florida using the travel cost method. The results from a count data regression model reveal that on average visitors would pay 74.18 dollars per visit-day for nature-based recreation resulting in a total economic value of 484.56 million dollars attributable to nature-based recreation in the Apalachicola River region. Results of this study provide useful information for natural resources management in the region and a rationale to preserve Florida's unique ecosystems.     

The effects of operational sex ratio and food deprivation on copulation duration in the water strider (Gerris remigis Say)

Summary A North American water strider, Gerris remigis (Hemiptera) copulates for prolonged periods of time, apparently beyond the time necessary for insemination (Rubenstein 1984; Wilcox 1984; Clark 1987), I tested predictions from two different hypotheses of the adaptive significance of this behavior. Manipulations of the operational sex ratio in artificial streams revealed that water striders copulate significantly longer when the sex ratio is male-biased. This result is consistent with the hypothesis that prolonged copulation functions as a type of contact mate guarding, which reduces sperm competition by preventing the female from remating prior to oviposition. The finding is also consistent with the hypothesis that copulation is prolonged to enhance female foraging efficiency. In a second experiment, sex ratio and total population density were held constant, and the period of food deprivation of females was manipulated. Contrary to the predictions of the female foraging hypothesis, starved females did not copulate longer than fed females. Of the two hypotheses considered, only the copulatory guarding hypothesis explains both results. This does not mean, however, that there is no selective benefit from the enhanced foraging efficiency resulting from prolonged copulation. Nor does it exclude the possibility that this benefit has been necessary for the evolution of prolonged copulation in water striders.