VTechWorks Repository :: Browsing by Author "Oderwald, Richard G."

Browsing by Author "Oderwald, Richard G."

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Acid deposition effects on soil chemistry and forest growth on the Monongahela National Forest
Elias, Patricia Elena (Virginia Tech, 2008-07-28)
Acid deposition (AD) results largely from the combustion of fossil fuels, and has been found to negatively impact forest ecosystems. AD may acidify soils through base cation leaching or Al mobilization, may cause accumulation of nitrates and sulfates in soils, and in some cases has been related to forest decline. The Monongahela National Forest (MNF) lies downwind from many sources of AD pollution, and average deposition pH is around 4.4. Therefore, managers are concerned about the possible deleterious effects of AD on the forest ecosystem. During the 2006 Forest Plan revision, evaluation of site sensitivity to acidification was specifically stated as a step in the Forest's adaptive management process. To meet this management objective, forest practitioners must understand the effects AD has on the forest, prescribe appropriate practices, and be able to monitor for future changes. To address the needs of MNF managers we used Forest Inventory and Analysis (FIA) sites to evaluate forest growth patterns on the Forest and determined the relationship between growth and key indicators of soil acidity. Furthermore, we used those relationships to create a map of site resistance to acidification across the MNF. To further develop a monitoring scheme we assessed two soil sampling protocols and two soil analysis methods for their suitability for monitoring AD-related changes in soil chemistry. Additionally, we evaluated the utility of dendrochronological and foliar sampling as AD-specific monitoring methods. Across all FIA sites on the MNF periodic mean annual volume increment (PMAVI) ranged from -9.5 m³ha⁻¹yr¹ to 11.8 m³ha⁻¹yr¹, suggesting lower-than-expected growth on two-thirds of the sites. Growth was compared to soil indicators of acidity on 30 FIA sites. In the surface horizon, effective base saturation (+), Ca concentration (+), base saturation (+), K concentration (+), Fe concentration (-), Ca/Al molar ratio (+), and Mg/Al molar ratio (+), were correlated with PMAVI (p ≤ 0.1). In the subsurface horizon pH_(w) (+), effective base saturation (+), Al concentration (-), and K concentration (-) were correlated with PMAVI. Site resistance to acidification was mapped based on site parent material, aspect, elevation, soil depth, and soil texture. There was a significant (p ≤ 0.1) positive correlation between PMAVI and a resistance index developed using five soil and site factors. Resistance was also compared with key soil indicators of AD-induced decline on 28 sites across the forest, and pH, effective base saturation, and Al content were found to be the best indicators related to resistance index. Resistance index was used to create a map of the MNF, of which 14% was highly resistant (RI ≥ 0.7), 57% was moderately resistant (0.7 > RI > 0.45) and 29% was slightly resistant (RI ≤ 0.45). The first of our monitoring program evaluations compared soil sampling and analysis methods on 30 FIA plots. Analyses of variance showed that soil pH, effective base saturation, Ca/Al molar ratio, and sum of bases varied significantly with sampling protocol. We also compared lab analyses methods and found that if sampling by horizon, a linear relationship can be used to estimate Ca/Al_SrCl₂ ratio using NH₄Cl extractions. The second monitoring approach evaluated the utility of a northern red oak (Quercus rubra L.) dendrochronology on two FIA plots. This analysis suggests that pollution on the MNF caused a decrease in growth rate during the 50-year period from 1940 to 1990. There were no differences among ring width increment and basal area increment between the two sites. From 1900 to 2007 the two sites showed 58.5% similarity in growth trends, but these could not be attributed to a dissimilar influence of AD. The third monitoring approach evaluated the relationship between foliar and soil chemical indicators. Across FIA plots, nutrient concentrations varied by tree species. The first year results from a potted-seedling study suggest that soil acidity influences growth, and foliar concentrations are related to growth rates. This evaluation of the effects of AD on the MNF can be used to develop adaptive management plans and a monitoring program that will meet the AD-related objectives of the 2006 Forest Management plan.
Analysis of Red Oak Timber Defects and Associated Internal Defect Area for the Generation of Simulated Logs
Winn, Matthew F. (Virginia Tech, 2002-12-05)
Log sawing simulation computer programs can be a valuable tool for training sawyers as well as for testing different sawing patterns. Most available simulation programs rely on databases from which to draw logs and can be very costly and time-consuming to develop. In this study, a computer program was developed that can accurately generate random, artificial logs and serve as an alternative to using a log database. One major advantage of using such a program is that every log generated is unique, whereas a database is finite. Real log and external defect data was obtained from the Forest Service Northeastern Research Station in Princeton, West Virginia for red oak (Quercus rubra, L.) logs. These data were analyzed to determine distributions for log and external defect attributes, and the information was used in the program to assure realistic log generation. An attempt was made to relate the external defect attributes to internal defect characteristics such as volume, depth, and angle. CT scanning was used to obtain internal information for the five most common defect types according to the Princeton log data. Results indicate that external indicators have the potential to be good predictors for internal defect volume. Tests performed to determine whether a significant amount of variation in volume was explained by the predictor variables proved significant for all defect types. Corresponding R2 values ranged from 0.39 to 0.93. External indicators contributed little to the explanation of variation in the other dependent variables. Additional predictor variables should be tested to determine if further variation could be explained.
An Assessment of the Utility of a Non-Metric Digital Camera for Measuring Standing Trees
Clark, Neil A. (Virginia Tech, 1998-09-18)
A method is set forth which makes use of a commercially available, non-metric, solid-state matrix camera to capture spatial and spectral data from an individual tree bole that can be used to measure characteristics about the stem. In this study diameters and heights were measured and used to estimate the volume of 20 red oak (Quercus spp.) stems ranging in diameter at breast height from 16 to over 60 cm and height from 12 to 20 meters. Images were taken from four orthogonal directions around the each stem. Diameter estimates from matching camera to stem distances (3 to 15 meters) of opposite sides were arithmetically averaged. Two arithmetic averages from perpendicular directions were then geometrically averaged. It was found that locating the camera farther from the tree led to more consistent results over the entire stem while locating it closer to the tree provided the most precise estimates provided the inclination angle did not exceed 45 degrees. This method resulted in geometric mean diameter estimates within ± 4 cm for all heights combined when obtained at a distance of 12 m or greater using a 95 % chi-square maximum anticipated error statistic. Error increases with increased stem height from ± 3 cm to ± 7 cm for heights from 1 to 20 meters. In general, the error is equivalent to 3 times the instrument precision, which varies with distance. Two-thirds of the time volume estimates were within 8 percent, which is quite an improvement over the 30 percent interval afforded by an appropriate volume equation.
A Biosocial Case Evaluation of Wood Biomass Availability Using Silvicultural Simulations and Owner Intentions on Family Forests in Virginia and North Carolina
Brinckman, Matthew Douglas (Virginia Tech, 2010-05-17)
Interest in wood-based bio-energy systems in the United States is increasing and may play a part in future renewable energy initiatives (Dincer 2000). Family forests have potential to play an important role in supplying wood biomass for energy production. However, access depends mostly on the management intentions among family forest owners. Enhanced biomass markets in regions where family forest ownership dominates could increase productivity by reinvigorating the low-value merchandizing required to accomplish silvicultural objectives. Given diverse owner objectives and forest types on family forests, estimates of biomass availability must include both biophysical and social aspects of procurable feedstock. This thesis chronicles a biosocial case study that estimates potential biomass supply from 51 family forests in Virginia and North Carolina. The study occurred within a woodshed centered on the future site of an impending ethanol plant in Mecklenburg County, Virginia. A survey instrument using the theory of planned behavior was used to measure ownership characteristics and intention to harvest. Forest attributes were collected during property visits to estimate potential yields resulting from silvicultural simulations. Results reveal that forest cover-type and tree size significantly affect owner intentions to harvest and owner attitudes toward harvesting partially mediate this relationship. Outputs from silvicultural simulations correspond with those made using Forest Inventory and Analysis data within the study region. Disproportionality was examined by coupling social and biological drivers of sustainable wood biomass availability. Implications of the research include refined estimates of potential supply and demonstrating a multi-scalar, mixed-method approach for assessing wood biomass availability.
Carbon Pools and Fluxes as an Indicator of Riparian Restoration
Giese, Laura (Virginia Tech, 2001-01-12)
Riparian forests are integral components of the landscape. The inherent biogeochemical processes that occur in such forests provide numerous benefits to wildlife and society. Maintaining good water quality is a major benefit from riparian forests and therefore, the maintenance, creation, or restoration of riparian forests is indispensable. This study was designed to broaden current knowledge of the complex, interrelated biogeochemical processes and determine indices for riparian forest restoration based on the various carbon pools/fluxes that may represent restoration success. This study was implemented on the Savannah River Site, an Environmental Research Park, where several riparian forests are recovering from thermal disturbances. The streams in these forests were subjected to thermal discharges that increased flows and resulted in removal of soil and a decline in the amount of woody vegetation. Two of these riparian forests are at different ages post-disturbance and represent different stages of recovery, which provides an exceptional opportunity to study successional processes in riparian forests and enhance restoration efforts. Linear transects perpendicular to the main stream channels were established in 2 recovering riparian forests of different ages (two areas in Pen Branch ~ 8 years post-disturbance; Fourmile Branch ~ 12 years post disturbance) and an undisturbed (thermally) more mature riparian forest (Meyer's Branch ~ 60 years). Along these transects quantitative data were obtained on above and belowground carbon pools and fluxes. Carbon pools exhibited a close correlation with riparian forest development. Biomass and carbon pools increased with increasing riparian forest stand age. The importance of the herbaceous carbon pool declined relative to the total above ground biomass, and the root carbon pool increased with forest age/succession. In general, net primary production (NPP) in young riparian forests (~8-10 years) rapidly approached and even exceeded NPP of more mature riparian forests. Once the herbaceous stage of succession was surpassed, the litterfall component of NPP plays a greater role riparian forests. As a woody overstory became established (after ~ 8-10 years), annual litterfall rates as a function of NPP were independent of forest age. Establishment of woody species occurred ~8 to 10 years after thermal disturbance and litterfall amount in young riparian forests rapidly became comparable to mature riparian forests. Lateral litter movement from the riparian forest toward the stream was less than the amount of litter (carbon pool) deposited from upstream into the riparian forest during a flood event. Overall lateral litter movement supplied less energy to the stream system than vertical inputs. A decline in riparian forest floor biomass was observed with increasing riparian forest development. However, a difference in foliar forest floor percent carbon lended itself to a minimal increase in the forest floor carbon pool with increasing riparian forest age. Woody debris in riparian forests comprised a relatively small carbon pool compared to tree and soil carbon pools. The species composition of litter appeared to be more of an overriding factor influencing decomposition rates than forest age. The influence of litter quality was evident in the decomposition rates of the different litter composites used in this study. In all 4 sites the litter composite from the mature riparian forest decomposed significantly more than the litter composites from the younger riparian forests. The fairly rapid decomposition of red maple (Acer rubrum L.), which was one of the main components in the mature riparian forest litter composite, influenced the greater decomposition rate. The litter composites from the younger riparian forests were similar and both included more decomposition resistant litter types, specifically waxmyrtle (Myrica cerifera L.) and alder (Alnus serrulata (Ait.) Willd.). Decomposition rates did not differ between the individual successional stages. Riparian forests are intimately associated with their hydroperiod. During flood events the riparian forest receives inputs of organic matter and sediment, and the amount of deposition may decrease along a distance gradient from the main stream channel. The differential amount of inputs could affect forest productivity. However, in these riparian forests, a distance gradient effect was not observed. Trends in herbaceous biomass were evident along a microtopographic moisture gradient. The ridge and swale microtopography prevalent in the younger riparian forests counteracted a distance from the stream channel gradient effect across the riparian forest. This study provided knowledge of how carbon pools and fluxes change with riparian forest recovery from disturbance as well as through different seral stages. Implementing the findings of this study will enhance restoration evaluation efforts to ensure that these areas continue to provide the numerous benefits gleamed from them.
Characterization of Vascular Plant Species Composition and Relative Abundance in Southern Appalachian Mixed-Oak Forests
Hammond, Daniel N. Jr. (Virginia Tech, 1997-12-16)
Eight study sites were established in mid-elevation, south aspect, mixed-oak forests in the Ridge and Valley and Allegheny Mountain physiographic provinces of Southwestern Virginia and West Virginia to address questions concerning the variability in species composition, richness, and relative abundance of vascular plant species in those communities. All forest strata were sampled using a nested plot design. Variability in species richness and species composition was found to be high. Total species richness values ranged from 84 to 273, and Sorrenson's Coefficient of Similarity index values indicated that approximately 46, 38, and 51 percent of the species in the overstory, mid-story, and herb stratum were the same among sites, respectively. However, despite differences in composition and richness, K-S tests revealed significant differences in the distribution of ranked relative abundance only in the mid-story at two sites. Differences did occur in the relative abundance of twelve growth form categories. While tree seedlings and perennial herbs dominated, on average, woody vines and fern species represented substantial coverage on sites in the Allegheny Mountains. Correlations among forest strata were weak. The greatest amount of variation in species richness was attributiable to the standard deviation of a forest site quality index (FSQI), which was thought to represent the variation in microtopography across each site. The lack of correlation and high variability in plant species richness and composition, despite similarities in topographic characteristics, reinforce the inherent weaknesses involved with using the chronosequence approach to studying ecological responses in the Southern Appalachian mixed-oak region. Future remeasurement and long term monitoring of these study sites, following the implementation of silvicultural manipulations, will provide the information needed to make inference on the effects of forest management practices on Southern Appalachian mixed-oak forests.
A comparative analysis of wood-supply systems from a cross- cultural perspective
Laestadius, Lars (Virginia Tech, 1990-07-06)
An analytical tool must combine sufficient scope with cultural neutrality to be adequate for analyzing problems across technological style boundaries. The concept of a wood-supply system is proposed, defined as a mechanism generating a consistent flow of wood to a set of wood-consuming mills, beginning its work with the severing of trees and ending it by feeding a pulping digester or head saw. The contrast in wood flow between the wood-supply systems of the Southern United States and Sweden is explored. The systems accommodate surges in wood-consumption rates and changes in wood-supply difficulty differently .. The South maintains a small wood inventory by keeping considerable production capacity idle; Sweden keeps little capacity idle by maintaining a large cushion of wood inventories. The implications of differences in relative cost between wood in inventory and forcibly idle production capacity are discussed. As a result of the historically motivated emphasis on accounting for capacity in Sweden and for wood in the South, costs associated with wood inventories and idle capacity appear to have been overlooked in a mirror-image pattern. The transfer of equipment between harvesting styles whose evolution has been governed by different relative costs has a high risk of failure. Southern equipment is cheap, uncomplicated. robust, and dependable in order to survive forced idleness and to produce without buffer inventories. Swedish equipment is expensive, complex, sensitive, and less dependable, due to the freedom to produce at capacity and the occurrence of large buffer inventories. Equipment manufacturers need to estimate the relative cost of idle wood and idle capacity when analyzing equipment exports across style boundaries. Suggestions for further work include an exploration of the relative cost in each region, and the development of unbiased methods of accounting for idle resources. It is also suggested that the different interpretations of the concept of forestry in Europe and North America be explored.
Components of logging costs
Loving, Easton (Virginia Tech, 1991-06-15)
Twenty-four independent logging businesses in the Southeastern United States were analyzed in a general systems approach to document the components of logging costs for mechanized operations, assess the sensitivity of these components to external stimuli, and to identify and describe the business management techniques adopted by contractors to insure survival and profitability. The contractors' cost records for 1988 and 1989 were analyzed to meet the study's first two objectives and interviews with each participant facilitated identification of survival and profitability strategies. The general interviews and on-site observations of the harvesting systems provided background information for evaluating the costs and identifying business management techniques. The contractors' records were summarized into six cost components: 1) consumable supplies, 2) labor, 3) equipment,4) insurance. 5) contract hauling, and 6) administrative overhead. Contractors were stratified by trucking strategy, ranging from those who hauled all of their own wood to contractors relying exclusively on contract truckers. Consumable supplies, labor, and equipment accounted for approximately 75% of total costs for the average contractor in 1988 and 1989. The concept of excess logging capacity was evaluated. Analyses indicate that excess capacity exists in many areas of the Southeastern U.S., and excess capacity influences cost structures and survival strategies. Discussion with most contractors and evaluation of direct costs of excess capacity indicated that contractors are unable to achieve marginal efficiencies due to the large number of suppliers in some areas. Four major business survival strategies were identified during the study. Equity dissolution and diversification were the prevalent strategies, suggesting that the late 1980s and early 1990s favor harvesting systems that are downwardly elastic in terms of production.
Cost and Productivity Analysis of Southeastern U.S. Logging Contractors from 1996 to 1997
Omohundro, Christopher Colon (Virginia Tech, 1999-03-19)
A group of 22 independent southeastern U.S. logging contractors provided 44 contractor-years of detailed cost and production information. Information was collected on demographics, operational characteristics, and business strategies for the participants. Precipitation was statistically proven to not be a good predictor of production, accounting for 2% of the weekly variation. High production through periods of favorable harvesting did not occur. Loggers contracting for the same mill in the same general area had higher than average production in the winter months and lower than average production in the summer months. Summary analyses for the entire population found that the cost of producing an additional ton dropped in 1997 by $0.90, but fixed annual costs rose. Predicting costs on the basis of production for the population was misleading. A comparison of total costs for individual firms with the population average (regression equation) found that the equation underestimated costs by as much as $408,000 and overestimated costs by as much as $528,000. Contracted services expenditures increased in 1997, as expenditures for equipment, consumables, and labor decreased. Over the study period, total costs per ton increased by 3.7%, but total production increased by 3.9%. The relationship between key cost components revealed strong evidence to disprove previously held theories. A major portion of the population increased production but experienced increased costs per ton. Replacement purchases of equipment tended to be of similar capabilities and technology and did not reduce labor costs. Trends in supply and equipment costs per-unit were not found in the expected fashion.
Design and testing of a prototype in-line chip quality monitor
Auel, John B. (Virginia Tech, 1996-09-06)
This project involved the design and testing of a prototype in-line chip quality monitor for gathering process control information for the manufacturers of wood chips. This monitor specifically addresses three common complaints with current chip sampling procedures. Chip sampling occurs too late in the process. It is inadequate. It is too infrequent to develop management information. The monitor is composed of a double screen drum separator to divide chips into oversize, accepts, and pins/fines. Counterbalanced tip buckets are used to weigh each size class. Tip bucket cycles are recorded by a computer via magnetic proximity switches attached to each bucket. This information is then used to chart production of chip size classes, updated continuously over the sorting period. This monitor is capable of sorting one ton of chips per hour. Two trials were conducted to test the monitor. One in a lab environment, and one on site at a chip mill. Both trials compared monitor output with independent samples classified using a Williams classifier. The trials showed that outputs were consistent with Williams output. This monitor can effectively chart chip distribution information. This process control information provides the manufacturer with immediate knowledge of chipper performance.
Design and testing of a sawdust dryer and a suspension sawdust burner
Egolf, Arthur R. (Virginia Tech, 1992-05-05)
The objectives of this research were to modify and test a prototype sawdust dryer designed by Arrowhead Forest Products and a sawdust-fueled suspension burner developed at Virginia Tech. The dryer was designed to process green sawdust at small to medium-sized sawmills and pallet mills. The sawdust burner was designed to be the heat source for the dryer and serve more general needs. A series of trials were conducted to develop the operating parameters of the dryer and measure the dryer's effectiveness at reducing moisture content to 0%. Separate tests were conducted on the burner to determine maximum heat outputs and combustor efficiencies using sawdust fuel of various moisture contents and particle sizes. The sawdust dryer proved capable of reducing the moisture content to 0% after several passes through the system. The sawdust burner produced close to 400,000 BTU's/HR at calculated efficiencies over 90% and proved relatively insensitive to ranges of fuel moisture contents and particle sizes.
Detection and prediction of biodiversity patterns as a rapid assessment tool in the tropical forest of East Usambara, Eastern Arc Mountains, Tanzania
Sengupta, Nina (Virginia Tech, 2003-11-20)
As a strategy to conserve tropical rainforests of the East Usambara block of the Eastern Arc Mountains, Tanzania, I developed a set of models that can identify above-average tree species richness areas within the humid forests. I developed the model based on geo-referenced field data and satellite image-based variables from the Amani Nature Reserve, the largest forest sector in the East Usambara. I then verified the model by applying it to the Nilo Forest Reserve. The field data, part of the Tanzanian National Biodiversity Database, were collected by Frontier-Tanzania between 1999 and 2001, through the East Usambara Conservation Area Management Program, Government of Tanzania. The field data used are rapidly collectible by people with varied backgrounds and education. I gathered spectral reflectance values from pixels in the Landsat Enhanced Thematic Mapper (Landsat ETM) image covering the study area that corresponded to the ground sample points. The spectral information from different bands formed the satellite image-based variables in the dataset. The best satellite image logistic regression and discriminant analysis models were based on a single band, raw Landsat ETM mid-infrared band 7 (RB7). In the Amani forest, the RB7-based model resulted in 65.3% overall accuracy in identifying above average tree species locations. When the logistic and discriminant models were applied to Nilo forest sector, the overall accuracy was 62.3%. Of the rapidly collectible field variables, only tree density (number of trees) was selected in the logistic regression and the discriminant analysis models. Logistic and discriminant models using both RB7 and number of trees recorded 76.3% overall accuracy in Amani, and when applied to Nilo, 76.8% accuracy. It is possible to apply and adapt the current set of models to identify above-average tree species richness areas in East Usambara and other forest blocks of the Eastern Arc Mountains. Potentially, managers and researchers can periodically use the model to rapidly assess, monitor, update, and map the tree species rich areas within the forest. The same or similar models could be applied to check their applicability in other humid tropical forest areas.
Developing a Natural Resource Database for Geographic Information System
Hassouna, Khaled M. (Virginia Tech, 1997-03-13)
Geographic information systems ( GIS ) are an effective tool for land management. By studying the land formations and land cover of a site, much information about the tree and animal species inhabiting a site can be estimated. The managers of public or private lands may find the concept of a multi-layer analysis of their land useful in discriminating locations based on their many characteristics. I created a database of a small area with no previously specified objective. I produced a group of map layers emphasizing the methodology and the ability of making any number of overlays or combinations of layers. I estimated the time and cost involved in producing these layers. I produced layers of: elevation, slope, aspect, watershed-depression, watershed-flow direction, watershed-streams, and roads. I created a group of categorized data layers: elevation, slope, aspect, erosive slope, watershed-flow accumulation, buffered roads, and buffered streams. I made some combinations of different layers explaining the potential uses of such combination. I used the work of my graduate colleagues to illustrate the importance of such work when combined in natural resources management. Combinations were made of: forest cover, average temperature, solar radiation, and slope position.
Development of a method for implementing group selection in Appalachian hardwoods
Boucher, Britt A. (Virginia Tech, 1989-05-05)
A method is described for implementing group selection regeneration in Appalachian hardwoods. The diverse set of definitions of the method, and the current forest demands are combined to form a flexible system of implementation that can accommodate public as well as private forests. Group selection is used where an uneven-aged silvicultural system is required and multiple objectives demanded. Several types of information are collected in a sample of the forest and then used to make the selection decision of which groups of trees to remove, and which groups to leave.
Diameter Distributions of Juvenile Stands of Loblolly Pine (Pinus taeda L.) with Different Planting Densities
Bullock, 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.
Dimensionally Compatible System of Equations for Tree and Stand Volume, Basal Area, and Growth
Sharma, Mahadev (Virginia Tech, 1999-10-28)
A dimensionally compatible system of equations for stand basal area, volume, and basal area and volume growth was derived using dimensional analysis. These equations are analytically and numerically consistent with dimensionally compatible individual tree volume and taper equations and share parameters with them. Parameters for the system can be estimated by fitting individual tree taper and volume equations or by fitting stand level basal area and volume equations. In either case the parameters are nearly identical. Therefore, parameters for the system can be estimated at the tree or stand level without changing the results. Data from a thinning study in loblolly pine (Pinus taeda L.) plantations established on cutover site-prepared lands were used to estimate the parameters. However, the developed system of equations is general and can be applied to other tree species in other locales.
Documentation of Productivity and Efficiency Relationships for a Group of Southern Logging Contractors
Walter, Michael J. (Virginia Tech, 1998-08-06)
A case study examined contractor demographics, business characteristics, costs and production information from twenty-three tree-length logging firms in six southern states from 1988 to 1994. Firms were evaluated in regard to the economic efficiency with which they converted inputs - dollars of capital, consumables, labor, overhead and insurance and contract hauling - into outputs - tons of wood delivered to the mill. While the firms exhibited a wide range of efficiency, average annual efficiency of all firms combined seemed to be relatively stable for the time period. Firms delivered between 20,000 and 250,000 tons of wood annually with a median of 61,000 tons. Coastal plain operations tended to be the largest, followed by piedmont, then Appalachian mountain operations. Annual production as a function of annual expenditures showed no obvious economies of scale in operation size. Most contractors increased annual production during the study, five contractors had production levels in the final year of the study that were less than their first year. Efficiency generally improved in firms that increased production gradually through better utilization of existing capacity. Contractors expanding their operations to increase productivity seemed to suffer efficiency losses more often than gains. Those firms that hauled their own wood had higher efficiencies than firms that contracted out trucking. There were no significant efficiency differences between loggers in the three physiographic regions within their respective trucking strategies. Efficiency generally declined as average annual hauling distance increased, however a regression equation explained only 18% of the variation in total economic efficiency.
Dynamic modeling of branches and knot formation in loblolly pine (Pinus taeda L.) trees
Trincado, Guillermo (Virginia Tech, 2006-06-15)
A stochastic framework to simulate the process of initiation, diameter growth, death and self-pruning of branches in loblolly pine (Pinus taeda L.) trees was developed. A data set was obtained from a destructive sampling of whorl sections from 34 trees growing under different initial spacing. Data from dissected branches were used to develop a model for representing knot shape, which assumed that the live portion of a knot can be modeled by a one-parameter equation and the dead portion by assuming a cylindrical shape. For the developed knot model analytical expressions were derived for estimating the volume of knots (live/dead portions) for three types of branch conditions on simulated trees: (i) live branches, (ii) non-occluded dead branches, and (iii) occluded dead branches. This model was intended to recover information on knots shape and volume during the simulation process of branch dynamics. Three different components were modeled and hierarchically connected: whorl, branches and knots. For each new growing season, whorls and branches are assigned stochastically along and around the stem. Thereafter, branch diameter growth is predicted as function of relative location within the live crown and stem growth. Using a taper equation, the spatial location (X,Y,Z) of both live and dead portion of simulated knots is maintained in order to create a 3D representation of the internal stem structure. At the end of the projection period information on (i) vertical trend of branch diameter and location along and around the stem, (ii) volume of knots, and (iii) spatial location, size and type (live and dead) of knots can be obtained. The proposed branch model was linked to the individual-tree growth and yield model PTAEDA3.1 to evaluate the effect of initial spacing and thinning intensity on branch growth in sawtimber trees. The use of the dynamic branch model permitted generation of additional information on sawlog quality under different management regimes. The arithmetic mean diameter of the largest four branches, one from each radial quadrant of the log (i.e. Branch Index, BI) and the number of whorls per log were considered as indicators of sawlog quality. The developed framework makes it possible to include additional wood properties in the simulation system, allowing linkage with industrial conversion processes (e.g. sawing simulation). This integrated modeling system should promote further research to obtain necessary data on crown and branch dynamics to validate the overall performance of the proposed branch model and to improve its components.
Effect of season of harvest and site quality on hardwood regeneration on the Virginia Piedmont
Kays, Jonathan (Virginia Tech, 1985-03-05)
Many existing Piedmont hardwood stands are composed of trees that are largely under 45 cm in diameter and contain a desirable oak component, as well as large amounts of undesirable red maple and sourwood. In stands under even-aged silviculture, season of harvest can be used as an effective management tool to favor different species compositions. If oak or other hardwood production is the management objective a dormant season harvest will result in increased sprout vigor of all oak as well as non-oak species. If pine conversion is the objective then a growing season harvest will reduce the vigor of all hardwood species and allow for easier competition control. The higher densities of all classes of regenerants on better sites indicates control will be more difficult.
Effects of European Gypsy Moth Defoliation in Mixed Pine-Hardwood Stands in the Atlantic Coastal Plain
Davidson, Christopher Bryn (Virginia Tech, 1997-10-28)
As populations of the European gypsy moth (Lymantria dispar L.) move into the southeast, laboratory studies indicate that the potential exists for defoliation and possible tree mortality in mixed pine-hardwood stands. This dissertation describes a field study that was initiated to determine the susceptibility and vulnerability of pure and mixed stands of loblolly pine, oaks and sweetgum in pine-oak and pine-sweetgum cover types in the Atlantic Coastal Plain physiographic province. Sixteen stands were defoliated between 1992 and 1996. Stand susceptibility was significantly related to stand composition; stands with a greater proportion of susceptible species experienced greater defoliation. Oaks and sweetgum were heavily defoliated. Pines did not suffer extensive defoliation, and results of the study indicate that the probability of widespread gypsy moth defoliation in pine plantations appears to be low. A multiple linear regression model for the prediction of mean stand defoliation is also presented. Trends in tree mortality were similar to those previously described in northeastern forests. Susceptible tree species were heavily impacted, however, oaks displayed greater vulnerability than sweetgum. Suppressed and intermediate trees in the understory, and trees that were in poor or fair condition, had a greater probability of dying subsequent to defoliation. However, under- and overstory basal area mortality rates were not significantly different in the pine-oak type, and stem mortality rates were not significantly different in either type. Loblolly pine mortality was observed, but it was difficult to isolate the source, and thereby determine whether gypsy moth defoliation was a primary causal factor. In general, the potential for extensive pine mortality in mixed pine-hardwood stands does not appear to exist. Logistic regression was found to be a useful tool in the prediction of individual tree mortality and two logistic regression equations were derived and validated for use in pine-oak and pine-sweetgum cover types.

Browsing by Author "Oderwald, Richard G."

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