Browsing by Author "Sharik, Terry L."

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    Equations for Estimating Above-Ground Phytomass in the Understory of Appalachian Oak Forests
    Martin, Wayne L.; Sharik, Terry L.; Oderwald, Richard G.; Smith, David William (Virginia Tech. Division of Forestry and Wildlife Resources, 1981)
    Regression equations were developed for estimating total aboveground phytomass for 17 tree and shrub species in the understory of second growth Appalachian oak forest stands in southwest Virginia. All possible combinations of three functional forms of the equation and three independent variables, singly and in combination, were tested. The linear model, with stem basal area as the independent variable, provided the best fit to the data for 15 of the 17 species. The exceptions were the blueberries (vaccinium stamineum and v. vacillans), where crown area performed better than basal area as the independent variable.
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    Evaluation of Ranked Set Sampling for Estimating Shrub Phytomass in Appalachian Oak Forests
    Martin, Wayne L.; Sharik, Terry L.; Oderwald, Richard G.; Smith, David William (Virginia Tech. Division of Forestry and Wildlife Resources, 1980)
    Ranked set sampling was introduced by McIntyre (1952) in estimating pasture yields. As described by McIntyre, the ranked set sampling procedure is implemented by first selecting a set of n elements at random from a population, and then raking those elements from lowest to highest by inspection of the variable of interest. The lowest ranked element is then measured. A second set of n elements is selected and ranked, and the second lowest element is measured. This process is continued until n such sets have been selected and n elements have been measured. The entire procedure can be repeated as many times as deemed necessary. McIntyre claimed that the ranked set estimator of the population mean was unbiased regardless of errors in ranking, and that with perfect ranking the variance of the mean from ranked set sampling would be less than that of random sampling when the number of measured elements is the same for both methods. Halls and Dell (1966) concluded that ranked set sampling was more efficient than simple random sampling in estimating pasture yields. A theoretical underpinning for ranked set sampling was provided by Dell and Clutter (1972), who also demonstrated that ranked set sampling is more efficient than random sampling even when errors in ranking are present. Ranked set sampling is clearly advantageous when measurement of an element is time consuming or costly and sample elements can be reliably ranked. The effectiveness of this technique has already been demonstrated for estimating forage and pasture yields. The objective of this study is to evaluate the effectiveness of ranked set sampling for estimating shrub phytomass in forest stands.
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    The influence of water and light on the physiology and spatial distributions of three shrubs in the Southern Appalachian Mountains
    Lipscomb, Mary Virginia (Virginia Tech, 1986-06-11)
    In order to understand vegetational gradients which develop in response to environmental gradients, the physiological capabilities of each species must be examined in relation to the observed environmental gradient. The distributions of three temperate zone shrub species which occupy different positions on the spur ridges of Brush Mountain may be influenced by their tolerances to light and moisture. Greenhouse studies indicate that R. maximum has a 60 % reduction in photosynthesis at water potentials below -1.0 MPa. R. nudiflorum has only a 30 % reduction and K. latifolia has less than 10 % reduction. Seasonal pressure volume curve determinations, conductance measurements, and water potential measurements of plants in the natural environment indicated that photosynthesis is not affected by water potential in K. latifolia. R. maximum has a significant reduction in conductance during drought which may limit photosynthesis. R. nudiflorum appears to begin senescence prior to severe drought in this area. Greenhouse experiments of adaptability to increasing light intensity show that K. latifolia and R. nudiflorum can significantly increase their light saturation point and maximum rate of photosynthesis in high light environments. R. maximum does not increase its photosynthesis rate in high light environments and appears to undergo chloroplast degradation when grown in high irradiance. Gradient analysis of vegetation on Brush Mountain shows that R. maximum reaches its highest importance in low light, high moisture sites. K. latifolia is most important in low moisture, high irradiance sites. R. nudiflorum is infrequent in the study area but occurs mostly in moderate moisture and irradiance sites. The distributions of R. maximum and K. latifolia appear to match their experimentally determined physiological tolerances. The results for R. nudiflorum are inconclusive.
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    Relationships between motivation and psychological distance in a forest recreation environment
    Hoar, Alexander R. (Virginia Tech, 1977-08-05)
    The purpose of this study was to field test a portion of the recreation quality theory: a conceptual framework which seeks to provide insight into the behavior of outdoor recreationists. Specifically, the inverse relationship of two variables which may affect the quality of outdoor recreation was examined. These were the force of motivation and the psychological distance to the user's destination in a recreation environment. Time spent hiking to the destination was considered a function of force, and physical distance was considered a function of the psychological distance to the destination. It was hypothesized that people who were able to accurately determine the distance remaining to the destination, as they were hiking along the trail, would arrive sooner than those who could not accurately determine the distance remaining to the destination. A map was used to provide users with information about· distances. The hiking times for 109 visitor groups at the Cascades Nature Trail in the Jefferson National Forest, Virginia were unobtrusively recorded between September 26 and November 7, 1976. Differences between the hiking times of groups were analyzed by means of Wilcoxon's Rank Sum Test, the Ansari-Bradley Dispersion Test, and the Moses Dispersion Test. The effects of changing environmental conditions were assessed by means of the Kruskal-Wallis Test for Multiple Comparisons, as well as by Wilcoxon's Rank Sum Test. This study provided evidence that supports the hypothesis proposed in the recreation quality theory, that an inverse relationship exists between the force of motivation and the psychological distance to a goal in a forested recreation environment.
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    Vegetational change resulting from forest conversion in the central Piedmont of Virginia and their implications for wildlife
    Felix, Antone Costa (Virginia Tech, 1981-05-15)
    Conversion of natural forest to loblolly pine plantations has become a common practice on commercial forest land in the central Piedmont of Virginia. To gain insight as to bow habitat conditions for wildlife vary over time, vegetation composition and structure were quantified in 21 converted stands at two state forests. The stands represented three replications of seven developmental stages ranging in age from 1 to 22 years. Six natural forest stands Which typify sites presently being converted were selected for comparison. The seral process can be exemplified by comparing vegetative changes in species richness, evenness, and vegetative coverage in the ground stratum (<1m). Richness and vegetative coverage showed the same trends: high values in stands 1 to 5 years of age followed by a decline from 5 to 15 years, at Which point canopy closure was complete and these variables were relatively stable for the next seven years. Evenness over time was fairly constant, except for three-rear-old stands where a decline occurred due to predominance by Andropogon virginicus. Trends in richness and evenness differed from the old-field successional model due to a diverse reservoir of propagative units at the initiation of succession and the rapid closure of the canopy by co-developing pines and sprout hardwoods. From an analysis of habitat variables, it appeared that one-year-old stands satisfied requirements of bobwhite quail and wild turkey; stands aged three years were deficient in food plants and probably too densely vegetated. Nine-year-old stands still provided browse for white-tailed deer. Post-canopy closure stands (15 to 22 yrs) were of little value to wildlife. In native forest stands (72 yrs), understory forage production was comparable to the post-canopy closure stands, while mast production, as estimated by Oak basal area and density, was more than adequate for good deer and turkey habitat. The present value of converted stands to wildlife depends on their size and interspersion with native forest and other cover types. Their future value could vary significantly depending on the silvicultural treatments applied.