Browsing by Author "Bullock, Bronson P."
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- Culture and Density Effects on Tree Quality in Midrotation Non-Thinned Loblolly Pine PlantationsGreen, P. Corey; Bullock, Bronson P.; Kane, Michael B. (MDPI, 2018-02-09)Six non-thinned loblolly pine (Pinus taeda L.) culture × density study sites in the Piedmont and Upper Coastal Plain of the Southeast U.S. were used to examine the effects of two cultural intensities and three planting densities on solid wood potential as well as the proportion and position of product-defining defects (forks, crooks, broken tops). A tree quality index (TQI) was used to grade stems for solid wood potential. The results show that an operational management regime exhibited a higher proportion of trees with solid wood product potential than did a very intensive management regime. Trees subject to operational management exhibited product-defining defects higher on the stem; however, the proportion of stems with defects was not significantly different from the intensive management. Planting densities of 741, 1482, and 2223 trees per hectare (TPH) exhibited a relatively narrow range of the proportion of trees with solid wood product potential that were not significantly different. Density did not have a significant effect on the heights of the product-defining defects. These results show that management intensity and less so planting density, affect the solid wood product potential indicators evaluated and should be considered when making management decisions.
- Diameter Distributions of Juvenile Stands of Loblolly Pine (Pinus taeda L.) with Different Planting DensitiesBullock, Bronson P. (Virginia Tech, 2002-02-08)Diameter distributions of juvenile loblolly pine (Pinus taeda L.) with different planting densities were characterized utilizing a two-parameter Weibull distribution. Trend analysis was employed to describe the effects of planting density, age, relative spacing, and rectangularity on the estimated diameter distributions for juvenile loblolly pine. A reparameterization of the two-parameter Weibull distribution was sought to reduce the dispersion of the estimated shape parameter. Methods that quantify the amount of inter-tree spatial dependency in a particular stand were applied. Empirical semivariograms were derived for each plot over all ages to enable spatial trend recognition. Moran's I and Geary's C coefficients were estimated for ground-line diameters from ages 2 to 5, and for breast height diameters from ages 5 to 11. Though there was no discernable trend in the presence of significant spatial autocorrelation with planting density, an initial negative trend with age was present, but leveled off by age 5. A conditional autoregressive model was utilized to evaluate the amount of spatial influence stems in a stand have on one another. The occurrence of significant spatial influences was positively associated with age through age 8, the trend then leveled off; no recognizable trend was detected with planting density. These indices help to describe stand dynamics that are influenced by the spatial distribution of stems. Models to predict the parameters of the two-parameter Weibull distribution were developed to aid in forecasting and simulation of juvenile loblolly pine. Simulations were conducted where a spatial dependency was imposed on the diameters within a stand. The spatial structure simulation enables accurate representations of stem characteristics when simulating forest stands that include spatially-explicit information.
- Modeling Green Weight of Loblolly Pine (Pinus taeda L.)Bullock, Bronson P. (Virginia Tech, 1998-12-17)Green weight and green weight per unit volume relationships for loblolly pine trees have not been studied extensively and models for predicting weights across broad geographic areas are not readily available. In this regard three basic interrelated issues were addressed in this study: 1) an examination of weight per unit volume relationships, 2) an assessment of how tree, stand, and geographic characteristics affect weight per unit volume relationships, 3) a derivation of models of weight per unit volume for predicting total bole weight and merchantable weight, 4) a derivation of models for predicting green weight directly, and 5) a comparison of objectives 3) and 4). This study showed that green weight per unit volume varies somewhat within stems, but the variation is large. There is no discernable trend by stand characteristics, and the geographic trends were inconclusive. Data from four data sets were combined and region-wide prediction models for total green weight, green weight to any upper merchantable diameter, and green weight to any upper merchantable height were developed for loblolly pine trees.