13,086 research outputs found

    Resistance of Scotch Pine Varieties to Zimmerman Pine Moth (Lepidoptera: Pyralidae) and Its Impact on Sales in a Choose and Cut Christmas Tree Plantation

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    Nine varieties of Scotch pine, Pinus sylvestris, were assessed for their susceptibility to Zimmerman pine moth, Dioryctria zimmermani, in a choose and cut Christmas tree plantation. Trees were examined for wounds to estimate their susceptibility to this pest 7 years after planting in the field. Numbers of trees remaining after seasonal sales in years 7 and 8 were used to estimate marketability of each variety. Infestation rates varied significantly among varieties (11-75%). After sales, proportions of trees remaining also varied significantly among varieties (7-52%). Although Belgian trees were the most moth resistant, they were the least purchased by the public, probably owing to their yellow-colored foliage. Excluding the Belgian variety, proportions of infested trees were positively related to the number of trees remaining after two years of sales (F=12.7 df = 1,22, R2=0.37, P\u3c0.002). This linear relation suggested that in a population of 100 trees, three trees must be wounded to cause one not to be sold. This implies that appearance of advanced damage symptoms such as brown and broken branches have a greater negative impact on sales than the simple presence of wounds

    Water on Mars: Inventory, distribution, and possible sources of polar ice

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    Theoretical considerations and various lines of morphologic evidence suggest that, in addition to the normal seasonal and climatic exchange of H2O that occurs between the Martian polar caps, atmosphere, and mid to high latitude regolith, large volumes of water have been introduced into the planet's long term hydrologic cycle by the sublimation of equatorial ground ice, impacts, catastrophic flooding, and volcanism. Under the climatic conditions that are thought to have prevailed on Mars throughout the past 3 to 4 b.y., much of this water is expected to have been cold trapped at the poles. The amount of polar ice contributed by each of the planet's potential crustal sources is discussed and estimated. The final analysis suggests that only 5 to 15 pct. of this potential inventory is now in residence at the poles

    Lime Needs and Trends in Arkansas

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    Consumption of agricultural lime in Arkansas declined significantly during the past seven years. During each of the past four years, lime consumption was lower than any time since 1960. The quantity of lime needed for optimum crop production on Arkansas\u27 soils is estimated to be 2,678,700 metric tons (MT) (3,000,000 tons), based on University of Arkansas soil testing summaries. Since 1980, less than 285,728 MT(320,000 tons) of lime have been used each year. It is the natural tendency for most soils in Arkansas to become more acidic with time. Periodic addition of agricultural limestone, however, can neutralize soil acidity and help to maintain soil productivity. Nitrogen fertilizers, applied for the production of most agricultural crops, may also contribute to the acidification of soils. The annual consumption of acid-forming nitrogen fertilizers in Arkansas increased from approximately 223,225 MT(250,000 tons) during fiscal year 1974-75 to about 392,876 MT(440,000 tons) by fiscal year 1983-84. At least 2.5 times more lime was needed than was used, just to neutralize the residual acidity from acid-forming nitrogen fertilizers alone, during the same period. Shifts in crop hectareages did not account for the magnitude of decline observed in lime consumption. If lime consumption does not increase in the future, and if acid-forming nitrogen fertilizer consumption follows the current increasing trend, soil acidity will cause a decline in the yields of acid-sensitive crops

    ECOLABELS AND ECONOMIC EFFICIENCY: SOME PRELIMINARY RESULTS

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    The public provision of information about the environmental performance of firms and products has generated considerable enthusiasm and become a common instrument of environmental regulation, even though the economic analysis of the social welfare properties of these policies is quite limited. This paper proposes a model for examining these properties.Research Methods/ Statistical Methods,

    Flatfish herding behavior in response to trawl sweeps: a comparison of diel responses to conventional sweeps and elevated sweeps

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    Commercial bottom trawls often have sweeps to herd fish into the net. Elevation of the sweeps off the seaf loor may reduce seafloor disturbance, but also reduce herding effectiveness. In both field and laboratory experiments, we examined the behavior of flatfish in response to sweeps. We tested the hypotheses that 1) sweeps are more effective at herding flatfish during the day than at night, when fish are unable to see approaching gear, and that 2) elevation of sweeps off the seafloor reduces herding during the day, but not at night. In sea trials, day catches were greater than night catches for four out of six flatfish species examined. The elevation of sweeps 10 cm significantly decreased catches during the day, but not at night. Laboratory experiments revealed northern rock sole (Lepidopsetta polyxystra) and Pacific halibut (Hippoglossus stenolepis) were more likely to be herded\ud by the sweep in the light, whereas in the dark they tended to pass under or over the sweep. In the light, elevation of the sweep reduced herding, and more fish passed under the sweep. In contrast, in the dark, sweep elevation had little effect upon the number of fish that exhibited herding behavior. The results of both field and laboratory experiments were consistent with the premise that vision is the principle sensory input that controls fish behavior and orientation to trawl gear, and gear performance will differ between conditions where flatfish can see, in contrast to where they cannot see, the approaching gear

    Differential Shoot Feeding by Adult \u3ci\u3eTomicus Piniperda\u3c/i\u3e (Coleoptera: Scolytidae) in Mixed Stands of Native and Introduced Pines in Indiana.

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    The larger pine shoot beetle Tomicus piniperda, a native bark beetle of Europe and Asia, was found in North American Christmas tree plantations in 1992 in Ohio. Subsequent surveys found it in six U.S. states and in one Canadian province. The first natural area where Tomicus was found to be established was at the Indiana Dunes State Park, in northwestern Indiana near the Lake Michigan shoreline. Pine stands were surveyed for fallen shoots to determine the extent and range of shoot feeding in the park. Within the study area adult Tomicus fed on the shoots of all native pines (Pinus banksiana, P. resinosa. and P. strobus.), as well as the European species (P. sylvestris). More fallen shoots were collected from both P. resinosa and P. sylvestris than expected from their basal areas in the sampled stands. This contrasted with P. banksiana and P. strobus whose shoots were underrepresented relative to their basal areas. The relatively high numbers of fallen shoots found for P. resinosa suggests that red pines in the Great Lakes region will easily support populations of T. piniperda

    Forecasting Realised Volatility using a Long Memory Stochastic Volatility Model: Estimation, Prediction and Seasonal Adjustment

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    We study the modelling of large data sets of high frequency returns using a long memory stochastic volatility (LMSV) model. Issues pertaining to estimation and forecasting of datasets using the LMSV model are studied in detail. Furthermore, a new method of de-seasonalising the volatility in high frequency data is proposed, that allows for slowly varying seasonality. Using both simulated as well as real data, we compare the forecasting performance of the LMSV model for forecasting realised volatility to that of a linear long memory model fit to the log realised volatility. The performance of the new seasonal adjustment is also compared to a recently proposed procedure using real data. --

    Carter-like constants of the motion in Newtonian gravity and electrodynamics

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    For a test body orbiting an axisymmetric body in Newtonian gravitational theory with multipole moments Q_L, (and for a charge in a non-relativistic orbit about a charge distribution with the same multipole moments) we show that there exists, in addition to the energy and angular momentum component along the symmetry axis, a conserved quantity analogous to the Carter constant of Kerr spacetimes in general relativity, if the odd-L moments vanish, and the even-L moments satisfy Q_2L = m (Q_2/m)^L. Strangely, this is precisely the relation among mass moments enforced by the no-hair theorems of rotating black holes. By contrast, if Newtonian gravity is supplemented by a multipolar gravitomagnetic field, whose leading term represents frame-dragging (or if the electrostatic field is supplemented by a multipolar magnetic field), we are unable to find an analogous Carter-like constant. This further highlights the very special nature of the Kerr geometry of general relativity.Comment: 4 page
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