In thinning, physical damage to the residual trees may result from abrasion during felling and yarding. The amount of damage is primarily a function of the stand geometry, the thinning prescription, and the felling strategy, under a given extraction system. In terms of controlling the level of damage, there are two interdependent aspects to the problem. One is to prescribe a desirable thinning that is compatible with the extraction system. The other is to efficiently engineer the extraction under the given silvicultural constraints. For skyline thinning it is assumed that a geometric model of the stand, and of the extraction system, provides a framework for examining potential physical damage, in terms of this interdependence. Based on a three-dimensional model, skyline thinning is simulated, and indices of potential damage are enumerated. For a sample stand of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), the potential damage is studied as a function of the prescription, and the system parameter that determines the felling directions. Three different selection prescriptions are examined; a Low, a Crown, and a Graded. The synthetic data is discussed in terms of frequency distributions, and as a function of the parameter mentioned. It is demonstrated that the system is very sensitive to this parameter. While the effect of the different prescribed thinnings might be thought to be intuitively obvious, some enigmatic phenomena are apparent. It is proposed that such a study is a means of examining both the silvicultural and engineering aspects of the problem of physical damage in the residual stand, for a skyline thinning system. It is hoped that such deliberation will provide a rational framework to determine the effect of this damage upon thinning regimes. / Forestry, Faculty of / Graduate

Numerous studies highlighted sharp declines in abundance of red oak species (Quercus spp., Section Erythrobalanus) in the southeastern United States. Red oaks are major components of bottomland forests, provide important ecological services, and are a critical source of hard mast for wildlife and high-value timber (Oliver et al. 2005). Bottomland hardwoods are usually managed with natural regeneration, and maintaining a component of red oak can challenge forest managers, given sporadic acorn production (masting behavior), and lack of advance regeneration establishment prior to disturbance. This study investigated the development of hardwood advance regeneration in relation to understory light availability and stand structure in mature closed canopy stands following silvicultural treatments. Improved understanding of red oak natural regeneration can better clarify any relationship between seedling abundance, available understory light, and residual basal area. Results will aid in selection of appropriate management techniques to sustain dominance of red oaks within bottomland hardwood forests.

Thesis (Ph. D.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 50-53). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1991. / Typescript (photocopy). Includes bibliographical references (leaves 64-69). Also available on the World Wide Web.

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Digitized by Kansas Correctional Industries

The uniform stretching model successfully accounts for the general features of many extensional sedimentary basins. However, the amount of extension measured across normal faults in the upper crust is often thought to be significantly less than that calculated from subsidence analysis and crustal thinning. At present, more complicated models, which incorporate two-layer stretching, multiple stretching phases and flexural rigidity, are used to explain this extension discrepancy. The principal aim of this dissertation is to show that the extension discrepancy can be resolved in the northern North Sea without abandoning the uniform stretching model. Other observations are also explained by minor changes to the model. Basin evolution is addressed both on a small and on a large scale. A kinematic model for hanging wall deformation, which is assumed to occur by arbitrarily inclined simple shear and by differential compaction, is proposed. Fault geometries can be calculated from sedimentary horizons within hanging walls using an inversion scheme based on this model. Results suggest that hanging wall shear is inclined towards the main fault. This implies that the amount of extension across a fault is considerably greater than the apparent horizontal displacement. Syn-rift footwall uplift is explained by combining the simple domino-style fault model with the uniform stretching model. The 'steer's head' cross-sectional geometry of sedimentary basins is usually explained either by fluctuations in sea-level or by increasing flexural rigidity of the continental lithosphere during post-rift cooling. Here, a two-layer stretching model is proposed, where the lithospheric mantle is stretched over a fractionally wider region than is the crust. This accounts for the observed extent of post-rift stratigraphic onlap in the North Sea and does not alter conclusions concerning the extension discrepancy. The geometrical and thermal consequences of lithospheric simple shear are investigated using a numerical model. Results predict that, as for the uniform stretching model, crustal thinning is symmetrical about the basin. Maximum thinning is also coincident with maximum subsidence. However, the magnitude of post-rift subsidence varies across the basin, allowing the uniform stretching model and the lithospheric simple shear model to be distinguished. The different models described here have been applied to regional seismic reflection profiles and well-log information from the northern North Sea. On the best constrained profile, the extension measured across normal faults agrees well with that calculated by subsidence analysis. The major observations are thus consistent with the predictions of the uniform stretching model.

This thesis includes a review of scientific studies of tree injuries following mechanized thinning. Interviews have been made with drivers of single grip harvesters and forwarders in forest thinning and a number of essential factors have been identified as the most important to take into account in order to minimize and/orprevent injuries to stems and roots of remaining trees.

The need for brushing before the first thinning has increased during the last few years. This brushing involves taking away small trees and bushes making it able for the harvester operator to see better and choose the correct trees to be harvested. In today’s silviculture the brushing is often neglected which means that the undergrowth becomes dense and leads to less efficiency for harvesters and a rise in costs. A well brushed first thinning will make the harvesting costs low and time efficient.   In brushing before the 1st thinning all stems below 9 cm d bh are traditionally taken down. This has a tendency to become stereotyped; i.e. brushes are also taken away in areas where  stronger nature conservation should be applied, as in wetlands, edge zones, etc. The harvester operator then gets stuck in these zones which threaten the biodiversity.    This study aims at examining two different types of brushing methods before the thinning, the traditional one and another (new) method where environmental and nature protection aspects were taken into account to a greater degree; i.e. where more stems and undergrowth have been left over and edge zones were not brushed. The study results show that the latter one is to prefer as the more cost efficient one. It also protects the harvester to drive out into the edge zones. This method is also beneficial for the wildlife.   Most harvester operators were positive to a new brushing manual.

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