Wet site timber harvesting often results in rutted and/or compacted soils. These impacts damage inherent site and soil properties and can reduce subsequent pine seedling survival and growth. Site preparation treatments such as bedding, disking, and fertilization are often employed on harvested sites to mitigate these impacts; however, their effectiveness has not been fully documented. Moreover, a distinction between rutting and compaction has not been made in previous research. This study’s objectives were to quantify the effects of rutting and compaction on site and soil properties and pine seedling growth and survival, and to quantify the effectiveness of bedding, disking, and fertilization in mitigating these impacts. Six wet pine flats were salvage logged following Hurricane Hugo in the fall of 1989. High soil moisture conditions during the salvage operations resulted in compaction and rutting damage. Two studies were established to quantify the effects of trafficking on the functions and productivity of wetland sites. One study addressed soil compaction while the other addressed soil rutting. Each study consisted of three sites, each containing four trafficked and four untrafficked plots. Four site preparation treatments, one on each disturbance plot, were installed in the fall of 1991. The four treatments were 1) no treatment, 2) bedding, 3) disking, .and 4) disking and bedding. The treatment plots were further split with half of each plot receiving 227 kilograms per hectare of 10-10-10 fertilizer. Genetically improved seedlings were hand-planted on the treatment plots in February, 1992. The site preparation treatments did not completely ameliorate compaction or rutting effects on pine seedling growth and survival. Rutting reduced pine seedling second-year height growth, total volume, and survival by 43, 90, and 9 percent, respectively. Compaction reduced second-year height growth by 31 percent and seedling survival by 14.5 percent. Bedding resulted in 35 and 106 percent greater second-year height growths and 117 and 421 percent greater seedling volumes than disking on the rutted and compacted sites, respectively. Phosphorous fertilization had an additive effect to the site preparation treatments and increased pine seedling height growth by 54 and 65 percent and seedling volume by 125 and 155 percent on the rutted and compacted sites, respectively. The factors that affected pine seedling growth and survival were water supply and movement and phosphorous supply. Management implications for wetland sites suggested by this study are as follows: 1) avoid rutting and compaction when possible, 2) schedule wet-site harvesting during the driest periods of the year, 3) use specialized wet-site harvesting equipment when needed, and 4) use bedding and fertilization for site preparation. / Master of Science

Harvesting of forested wetlands in the Atlantic and Gulf lower coastal plains has the potential to cause intense site disturbance. Often, as a result of poor pre-harvest planning, silvicultural activities are performed on wetland soils highly susceptible to rutting and puddling. Potential decreases in pine productivity have been connected with increased soil strength and decreased aeration that are commonly remnants of site disturbances associated with wet-weather harvesting. A simple and economical rating system is needed to identify soils susceptible to disturbance by various types of equipment. The use of such a system could lower the impact on wetland soils and lower the cost of extensive site preparation methods. Logging efficiency and operational productivity could also be increased by identifying equipment types compatible with site conditions. The purpose of this study was to characterize and model soil strength as a function of soil physical properties and site characteristics. The soil strength model was subsequently used to develop a trafficability hazard index. Forested wetland sites in the South Carolina coastal plain were characterized to develop the trafficability hazard index. The study site consisted of three blocks located on poorly drained loblolly pine plantations. Five sequences of measurements were taken consisting of soil moisture, water table depth, and soil strength. The five sequences of measurements were taken over a wide range of soil moisture contents and water table depths to characterize the effects on soil strength. Bulk density, porosity, texture, organic matter, and hydraulic conductivity were also determined to characterize the blocks and identify effects on soil strength. Evaluating the effects of these properties on soil strength identified two relatively easily determined soil properties that could be used for the trafficability index. Volumetric moisture content and penetration resistance of the A horizon were used due to their relationships with trafficability and ease of determination. Estimates of pressure applied to the soil by harvesting equipment were used to find the limits of the sandy loam A horizon to support various types of equipment. Equipment pressures were compared to soil penetration resistance pressures estimated by soil moisture. The trafficability hazard index presented used general ground pressures for various harvesting equipment, but use of specific equipment pressures would provide the best results. Using the trafficability hazard index, sites with less than optimal conditions for traffic can be avoided or special harvesting equipment can be identified to limit site disturbance. / Master of Science

M. S.

Graduation date: 1990

This study examines sediment storage and transfers in gullies of coastal British Columbia, and how logging affects sediment storage and transfers. Both fluvial and debris flow transport of sediment occur in gullies, and the amount of fluvial transport of sediment which occurs will affect the magnitude of a subsequent debris flow. Coarse woody debris (CWD) may affect the storage and transfer of sediment in the gully channel, and logging can affect the supply and type of CWD. To determine whether logging affects storage and transfer of sediment in gullies, sediment budgets were constructed for gullies in four treatment classes: A. Logged, slash full, no recent debris flows : "slash-full (SF)." B. Logged, slash removed, no recent debris flows : "slash-clear (SC)." C. Logged, naturally scoured by debris flows : "torrented (T)." D. Unlogged, naturally loaded with CWD : "unlogged (U)." Each sediment budget had input to the channel, storage in the channel, and output from the channel estimated. Significant differences between treatment types occurred, summarized below. Treatment classes grouped together (in brackets) did not have significant differences. Budget term : Input, greatest→least, Torrented→Slash-full→(Unlogged and Slash-clear). Budget term : Storage, greatest→least, Torrented→Unlogged→Slash-clear. Budget term : Output, greatest→least, Slash-clear→(Torrented and Unlogged)→Slash-full. One objective of the study was to assess the effectiveness and feasibility of cleaning slash from the gully channels. To be effective, cleaning slash must either reduce the magnitude of a debris flow in a treated gully, or else reduce the likelihood of initiation of a debris flow in the treated gully. Removal of slash will reduce the volume of a subsequent debris flow by about 15 percent, simply from the reduction in the amount of CWD. Reduction in sediment stored in the treated channel may reduce the volume of a debris flow by a further 4 percent. There is no evidence that removing slash will decrease the likelihood of initiation of a debris flow.

This study examines sediment storage and transfers in gullies of coastal British Columbia, and how logging affects sediment storage and transfers. Both fluvial and debris flow transport of sediment occur in gullies, and the amount of fluvial transport of sediment which occurs will affect the magnitude of a subsequent debris flow. Coarse woody debris (CWD) may affect the storage and transfer of sediment in the gully channel, and logging can affect the supply and type of CWD. To determine whether logging affects storage and transfer of sediment in gullies, sediment budgets were constructed for gullies in four treatment classes: A. Logged, slash full, no recent debris flows : "slash-full (SF)." B. Logged, slash removed, no recent debris flows : "slash-clear (SC)." C. Logged, naturally scoured by debris flows : "torrented (T)." D. Unlogged, naturally loaded with CWD : "unlogged (U)." Each sediment budget had input to the channel, storage in the channel, and output from the channel estimated. Significant differences between treatment types occurred, summarized below. Treatment classes grouped together (in brackets) did not have significant differences. Budget term : Input, greatest→least, Torrented→Slash-full→(Unlogged and Slash-clear). Budget term : Storage, greatest→least, Torrented→Unlogged→Slash-clear. Budget term : Output, greatest→least, Slash-clear→(Torrented and Unlogged)→Slash-full. One objective of the study was to assess the effectiveness and feasibility of cleaning slash from the gully channels. To be effective, cleaning slash must either reduce the magnitude of a debris flow in a treated gully, or else reduce the likelihood of initiation of a debris flow in the treated gully. Removal of slash will reduce the volume of a subsequent debris flow by about 15 percent, simply from the reduction in the amount of CWD. Reduction in sediment stored in the treated channel may reduce the volume of a debris flow by a further 4 percent. There is no evidence that removing slash will decrease the likelihood of initiation of a debris flow. / Arts, Faculty of / Geography, Department of / Graduate

The relationships between local and catchment-wide land use patterns and the spatial distribution of stream habitat variables within the Grande Cascapedia drainage basin were investigated using a geographic information system (GIS). Stream habitat variables including substrate composition and channel morphology were sampled at 48 study sites, ranging from highly disturbed to relatively pristine forest conditions in 2nd to 5th order tributaries. Land use and geology-structure variables were extracted for each catchment at four spatial scales using a GIS. The transition between pool-riffle and boulder-rapid morphologies occurred between channel gradients of 1.5% and 1.7%. The surface grainsize distribution is affected by the hydraulic power of the reach, while the subsurface grainsize distribution is associated with the degree of valley incision. The amount of logging within a 1 km radius of a sample site increases the occurrence of fine sediment within the substrate. There was, however, a surprising lack of relationship between the majority of road density metrics and the level of fines within the substrate.

Forest harvesting is blamed for a perceived increase in the flashiness and turbidity of the Cascapedia River's water. This has raised questions over the source of the sediment (harvest parcels, roads, or stream banks) and its potential impact on the sedimentology of the river. The objectives of this research are twofold. The first is to ascertain if harvesting operations are associated to a widening of low-order tributaries, creating a source of sediment. The second is to determine if variations in the sedimentology along four segments of the Cascapedia can be associated to harvesting operation intensity. Firstly, analysis of stream width in low-order tributaries shows that, once the variations associated with basin area and D50 are removed and within the range of harvesting in our dataset, there appears to be a 25% increase in width associated with the harvesting activities of the last five years, as well as with road density, both in a 60 m stream buffer for a number of the sampled streams. Secondly, the models relating harvesting intensity and changes in sedimentology are sensitive to a few sites or contrary to theory. Future studies should determine the underlying hydrological processes responsible for stream enlargement and the process of sediment deposition.

No description available.

No description available.