This study is based on a field trial at SLU in Alnarp. The idea behind the study was to see how interspecific competition influence density and annual rings on oaks (Quercus robur). The trial started out from four blocks with four different treatments. Those treatments that were initiated was: no competition, competition with herbs, competition with bushes and competition with herbs + bushes. Test samples from stumps were taken, with help from a hand saw. A total of nine samples were collected and divided on the four blocks with different competition types. With help from x-ray analysis, density and width for individual annual rings with distributed spring- and summerwood, each sample could be analyzed. The result of the study displayed that density and annual rings are affected by interspecific competition depending on type of competing vegetation. Herbs had a slight impact on annual rings, density and share of summerwood, while bushes had the biggest effect. Through the study measurements between different types of competitions it was possible to construe most effect on annual rings and share of summerwood but relatively small effect on density.

In recent years, interest in uneven-aged forestry has been increasing in Britain, particularly for sensitive areas such as recreation and amenity forests. Literature on the economics of uneven-aged forestry is scarce and few operational, uneven-aged forests are available for study. Therefore, in order to quantify the operating costs associated with uneven-aged forestry, a modelling approach was chosen. The resulting model is written in FORTRAN and uses a series of square two-dimensional arrays to represent a block of forest. The block may then be managed by clearfelling and replanting at a specified age, or by a system of group management with a choice of four group sizes. The resulting model was then used to investigate the effect of the following management strategies on operating times: 1. Varying the scale of working (i.e. the group size and forest size) in the uneven-aged forest. 2. Using shortwood or pole-length harvesting systems and a range of machine types within each harvesting system. 3. Varying the length of time taken to transform the structure of the forest from even-aged to uneven-aged. 4. Varying the age of the trees when the transformation from even-aged to uneven-aged structure begins. The results obtained from running the model show that the time taken to carry out an operation is influenced both by the absolute size of the group within the forest block and by the number of groups of that size within the forest block. This fragmentation effect explains why it is difficult to determine the absolute costs of working for a specific group size, because it is the combination of group size, number of groups and forest block size, which determines costs. Most of the results below are based on a range of group sizes from 1.000 ha. to 0.0625 ha., with a block size of 16 ha. Forwarders were penalized when the group size was decreased to 0.0625 ha. (-12% increase over clearfelling), because very small groups do not contain full forwarding loads and a large proportion of total forwarding time is spent manoeuvring into and out of groups. However, the operating times for the three group sizes 1.00 ha., 0.25 ha. and O. 1 1 ha. were very similar indicating that the group size can be quite small before any extra forwarding costs are incurred. On poor sites, the cost differential between the largest and smallest groups is greater. In contrast to forwarding, skidders are most penalized with the decision to adopt an uneven-aged system, and once that decision has been made, there is not a clear increase in costs with decreasing group size. During the transformation period, felling and thinning times in the uneven-aged system are significantly higher than those for the even-aged system, because trees are being harvested prematurely to create the early groups, but this difference is reduced once the forest is transformed. Felling and thinning times increase gradually as the group size decreases, because more care is needed for the felling operation and more time is needed for snedding coarse edge trees. Replanting times for the uneven-aged forest are approximately 8% - 14% higher than replanting times for clearfelling. The results from the model were then analysed using the EXCEL spreadsheet programme to examine, among other things, the cost implications of varying group size, and the relative profitability of uneven-aged and even-aged management. First,optimum ages to begin transformation were found, which varied with the Yield Class and discount rate chosen. Then, the effect of the length of the transformation period was examined and a long transformation period (80-years) was found to be preferable to a short transformation period (40-years). The analysis showed that at high discount rates even-aged and uneven-aged management had similar Net Present Values, but at lower discount rates the even-aged system was preferred. The greatest financial penalty was incurred with adoption of an uneven-aged system, and reducing the group size had relatively little impact on Net Present Values. Other costs and benefits, such as scenic beauty and recreation potential, could not be included in the model, because research relating these values to forest management variables has not been carried out. Therefore, these mostly non-financial factors were discussed for even-aged and uneven-aged forestry, based on a review of the literature.

Global environmental change represents one of the greatest challenges facing forest resource managers today. The uncertainty and variability of potential future impacts related to shifting climatic and disturbance regimes on forest systems has led resource managers to seek out alternative management approaches to sustain the long-term delivery of forest ecosystem services. To this end, forest managers have begun incorporating adaptation strategies into resource planning and are increasingly utilizing the outcomes of forest landscape simulation and climate envelope models to guide decisions regarding potential strategies to employ. These tools can be used alongside traditional methods to assist managers in understanding the potential long-term effects of management and climate on future forest composition and productivity. This study used a spatially explicit forest landscape simulation model, Landis-II, to examine and evaluate a range of long-term effects of current and alternative forest management under three projected climate scenarios within a 50,000-hectare forested landscape in southeastern Vermont, USA. Multiple scenarios were examined within this mixed ownership landscape, allowing for an evaluation of the influence of management and climate on future forest conditions in the region. These simulations indicate that land-use legacies and the inertia associated with long-term forest successional trajectories are projected to be an important driver of future forest composition and biomass conditions for the next 100 years. Nevertheless, climate is projected to have a greater influence on species composition and aboveground biomass over the next two centuries, with forests containing a greater abundance of species from more southerly regions and lower levels of aboveground biomass, resulting in shifts in the future provisioning of ecosystem services. Key words: Vermont, USA; climate change; forests; LANDIS-II; forest adaptation; forest management; above ground biomass; landscape inertia; land use recovery; forest composition

vi, 164 leaves : ill., tables, maps, photos ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1978) from the Dept. of Applied Mathematics, University of Adelaide

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Two studies concerning low molecular weight organic acids in soils were conducted. In the first study, anion exclusion chromatography was used to separate and identify 12 common organic acids, and the accuracy, precision and detection limits of the method were determined. The method was found to be sensitive and accurate to between 1.5 and 9 ��M, depending on the acid in question. The stability of the selected acids was examined, and the large concentration changes observed underscore the importance of timely analysis of soil solutions. No significant interferences were encountered in the analysis of two soil solutions. In the second study, the reaction of a forest soil with oxalic acid at four concentrations was monitored for a period of 96 hours. A large release of aluminum, sulfate, and phosphate was observed, with the greatest release occurring with the highest concentration of added oxalate. Solution aluminum increased by up to a factor of twenty, and though [Al�����] values were consistent with control by thermodynamic equilibrium with an amorphous aluminum oxide phase, exchangeable Al appeared to be the source of the increase. Sulfate increased abruptly at the start of the reaction and continued to rise, though more slowly, throughout the study. Solution phosphate was increased by up to four times and was maintained at the elevated level throughout the study. Changes in both sulfate and phosphate concentrations were attributed directly to exchange with oxalate. The persistence of elevated phosphate concentrations after 96 hours indicates that the effects of oxalate production by mycorrhizae could have lasting effects on the nutrient status of a soil. / Graduation date: 2000

Although there has been extensive research on the geomorphic and ecologic role of large woody debris (LWD) in streams, the dynamics of LWD in streams are poorly known due to various measurement difficulties during floods. In this thesis I present the results of two flume experiments on the dynamics of wood in streams. The first experiment examined the effects of piece interaction on wood transport, while the second evaluated a theoretical model predicting the threshold of movement, and factors controlling the deposition of individual logs. Flume experiments allow us to model the wood movement under a variety of piece geometries, piece concentrations, and hydraulic conditions. The first experiment showed that logs moved in three distinct transport regimes; congested, semi-congested, and uncongested transport. During congested transport the logs move as a single mass and occupy > 33 % of the channel area. Uncongested transport occurs when the logs are moving as individuals and occupy < 10 % of the channel area. Semi-congested transport is intermediate between these two transport regimes and occurs when wood moves in clumps of 2-3 logs. Transport regime was dependent upon the ration of the volumetric input rate of pieces to the flow, and to a lesser degree, the ratios of the piece length to channel width and piece diameter to channel depth. The transport regime was reflected in the deposit. Congested transport deposits have a higher portion of their pieces oriented parallel to flow than uncongested and semi-congested transport. We expect that congested transport will occur in low-order channels where input rates are high and channel geometry is small relative to piece size. Uncongested transport will dominate large channels where input rates are lower relative to flow and channel geometry is large relative to piece size. Our theoretical model and these experiments indicate that the entrainment of individual logs was dependent upon the angle of the piece, and the presence/absence of rootwads. Although previously noted as a first-order control on piece movement, piece length had little effect on the entrainment threshold, but did affect the distance transported. The distance transported decreased with increases in the ratios of the piece length to average channel width (L[subscript log]/w[subscript av]), the piece length to the radius of curvature (L[subscript log]/R[subscript c]), and the piece diameter relative to average depth (D[subscript log]/D[subscript av]). These three ratios comprise the debris roughness. Increased debris roughness caused a general decrease in distance transported. Pieces with high debris roughness can travel further than predicted if they have high momentum, and over 50 % of their channel area deeper than the depth at which the piece floats. These results indicate that flume experiments and theoretical models, tools that have been extensively used to study sediment dynamics, are a useful in examining wood dynamics. / Graduation date: 1998

Poly(lactic acid) / Cellulose Nanocrystals (PLA / CNs) were simultaneously electrospun to fabricate a novel renewable and biocompatible nanocomposite as potential scaffold for bone tissue engineering. CNs were successfully incorporated into the PLA fibers to reinforce the electrospun fiber mat. Thermal, chemical and mechanical analyses were performed to characterize and determine the properties of the scaffold fabricated. Highly porous fibers with fibers diameters in the range of 500-1000 nm were characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Crystallinity of the electrospun nanocomposite was studied by Differential Scanning Calorimetry. Adipose-derived human mesenchymal stem cells (hMSCs) were used to study the cytocompatibility of the nanocomposite scaffold. Life/dead cell assay was performed to determine cell viability of the scaffolds. After one week of cell culture, confocal microscopy indicated that the cells grown on the PLA / CNs nanocomposite were confluent and very well aligned along the fibers while cells cultured on pure PLA fibers were not as confluent as in the developed nanocomposite. This project has demonstrated the feasibility of the fabricated PLA/CNs nanocomposite as a potential scaffold for bone tissue engineering.

Thesis (M.S.)--Oregon State University, 1983. / Typescript (photocopy). Includes bibliographical references (leaves 46-51). Also available via the World Wide Web.