Cover states: Final Report submitted to the National Science Foundation / Grant No. ATM 79-24365 / Foreword states that this item is "in reality, a progress rather than a final report."

No description available.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 116-126). Also available on the World Wide Web.

M.Sc. / This study examined the disturbance and recovery patterns and processes of a subtropical dry forest in Southern Maputaland, South Africa in an attempt to determine how the forest areas interact with non-forest areas in the presence of human-induced disturbances. The KwaNibela Peninsula is an outcrop of land at the northern reaches of Lake St Lucia with patches of forest interspersed in a woodland matrix. The peninsula is inhabited by the local KwaNibela community who utilise the forest resources for a variety of purposes and the question is: how do the vegetation communities and species respond to these disturbances? The forest has increased in extent over the last 71 years; however the degree of forest patch fragmentation has also increased as a result of clearcutting areas of forest for homesteads, kraals, cropland and infrastructure. The floristic and structural changes from areas of core forest to the open woodland show that forest regeneration is taking place, particularly within the young, re-growth stages and certain shade-intolerant species only occur within the forest as mature individuals, with no recruitment under the forest canopy. The presence of open areas/gaps in and around the forest allows the recruitment of shade-intolerant species and this drives forest succession in a woodland environment. The resource use by the local community contributes toward the relatively high levels of regeneration and the forest in KwaNibela can be described as a young and dynamic KwaZulu-Natal Coastal Forest with affinities to related forest types. The vernacular names and uses of 82 plant species and eight animal species were recorded and compared to previously-recorded Zulu knowledge, as well as uses recorded elsewhere in Africa. A considerable number of species were found to have uses and vernacular names that are new to our current recorded knowledge and this study, therefore, reveals that the ethnobotanical knowledge of the Zulu ethnic group in Maputaland is incompletely recorded. A framework for sustainable resource use management was provided, based on the information collated during this study and it was ascertained that managerial efforts should focus on encouraging responsible resource use practices and promoting income and resource alternatives in the attempt to relieve pressure on forest resources while ensuring the long-term sustainability of forest-based livelihoods in this area.

No description available.

Ice (glaze) storms are frequent natural disturbances in eastern deciduous forests. Two opposing hypotheses exist in the literature regarding the effect of glaze on forest succession. In the first view, succession is said to be accelerated as pioneer species sustain greater damage than equilibrium species. The resistant equilibrium species would then fill canopy gaps, shifting the stand to a more advanced stage. Alternatively, extensive canopy damage allows more light to reach the forest floor perhaps favoring the germination and establishment of pioneer seedlings. Survival of these individuals would return the community to an earlier successional stage, or maintain pioneer communities. This study examined the response of the reproduction and susceptibility of tree species (by damage and mortality) two growing seasons after an ice storm, across a moisture and successional gradient. Four stands were studied: <i>Liriodendron</i>, mesic and xeric <i>Pinus</i>, and <i>Quercus</i>. Damage for most species was consistent across stands, with larger trees generally sustaining greater damage than smaller trees or saplings. Mortality increased with increasing stem size and severity of damage for most species. However, while damage to <i>Liriodendron tulipifera</i> was very high, actual mortality was low due to its ability to sprout. Also, because seedling reproduction of pioneer species was stimulated in this stand, succession appeared to be retarded. Succession was accelerated in the mesic <i>Pinus</i> stand where mortality of canopy trees was high and where removal of the canopy stimulated growth and sprouting of understory equilibrium species. Succession of the stands on drier sites (e.g. <i>Quercus</i> and xeric <i>Pinus</i>) appeared unaffected as the composition of tree seedlings remained essentially unchanged after disturbance. Thus, the response of a community to ice damage depends on the interrelated variables of vegetation composition, successional status, and topographic position. / M. S.

Rainfall interception is a primary control over the moisture input to a forested ecosystem through the partitioning of precipitation into throughfall, stemflow, and an evaporated component (i.e. the interception loss). Rainfall interception is a spatially and temporally varying process at multiple scales, but heterogeneity in interception processes are poorly understood and poorly described in the literature. We need to know how net precipitation varies in ecosystems because natural systems are driven by non-linear ecohydrological processes where mean values cannot capture localized effects or the cumulative consequences associated with an extremely heterogeneous input. In this thesis, we present two studies that investigate the heterogeneity of interception loss and throughfall in a forested catchment in the western Cascades range of Oregon. In one study, we examined the spatio-temporal patterns among point measurements of throughfall depth and isotopic composition to determine the cause of isotopic differences between throughfall and rainfall. Our results indicated that the residual moisture retained on the canopy from previous events plays a major role in determining the isotopic composition of the next event's throughfall. Differences between the isotopic composition of throughfall samples could indicate further partitioning of throughfall into various flow-paths from the canopy. The second project examined the question of how vegetation variability and terrain complexity drive interception loss heterogeneity at the whole-catchment scale. We applied a simple interception model to a watershed gridded at a 50 m resolution to investigate the relative importance of topographic and vegetative controls over the spatial variability of interception loss. We found that storm characteristics are crucial regarding the impact of spatial heterogeneities in vegetation and evaporation rates. In the Pacific Northwest climate, interception loss is not highly variable for the majority of the year because the annual precipitation is dominated by large storms with low interception losses. However, the net precipitation input to a watershed becomes extremely heterogeneous in the summer due to high interception loss variability. Summer interception loss could be an important control over the spatial variability of the availability of moisture, coinciding with when vegetation is most water-limited. / Graduation date: 2013

Commercial forestry is recognized for both its economic contribution as well as its environmental impact. Of particular concern, is the soil erosion and sedimentation of watercourses associated with forestry plantations. Environmental laws regulate many of the activities of the forestry sector. It is critical that the forestry sector ensure that its operations are compliant with the legal requirements that govern its use of natural resources. In pursuing legal compliance it is necessary to ensure that erosion control strategies are developed so as to ensure the positive effects of any interventions are optimised. The identification of areas that are particularly at risk to erosion or contribute to sediment delivery is an essential component in prioritising areas for management interventions. Establishing the erosion potential for commercial forestry areas is readily accomplished through the application of existing models. Process based erosion models generally have greater data requirements than the empirically derived USLE-based models. Given the paucity of data available, the latter approach was adopted. Two methods of topographic sub-factor derivation were investigated, those associated with the RUSLE (Renard, Foster, Weesies & McCool1991) and the Unit Stream Power method presented by Moore and Burch (1986). Since no existing methods identifying delivery risk areas existed, a method was developed based on principles and factors identified in the literature. Additionally, methods for identifying topographic assets, in terms of sediment attenuation, were developed. From these models three indices were derived; sediment supply, delivery risk and sediment attenuation. Thereafter, the mean Sediment Supply Index was divided by stream length for small catchments defined within the landscape to derive an index of sediment loading to streams. This index is used to identify priorities for management intervention across the landscape. The mean slope and sediment supply is used to develop buffer width recommendations for the streams draining the catchments, using a method developed by Karssies and Prosser (2001). Using the three indices in conjunction it is possible to make on-site and off-site erosion control recommendations as well as identify and exploit any natural features that can be utilized in erosion control. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002

The structure and composition of mixed-conifer forest (MCF) in central Oregon has been altered by fire exclusion and logging. The resulting increased density, spatial contagion, and loss of fire resistant trees decrease the resiliency of this ecosystem to fire, drought, and insects. The historical and current composition and structure of MCF are characterized by steep environmental gradients and a complex mixed-severity fire regime. This inherent variation makes it difficult to determine the magnitude of anthropogenic effects and set objectives for restoration and management. As a result, there is a lack of consensus regarding how MCF should be managed and restored across the landscape. My primary research objectives were to: (1) Characterize the current structure and composition of MCF and how these vary with environmental setting; and (2) Characterize establishment and tree growth patterns in MCF in different environmental settings. To address these objectives, I collected field data on structure and composition and increment cores across a range of environmental conditions in MCF of the eastern Cascades and Ochoco Mountains. I used cluster analysis to identify four stand types based on structure and composition in the eastern Cascades study area and four analogous types in the Ochoco Mountains study area. Variation in understory composition and the presence of large diameter shade tolerant species distinguish each type. Stand types occupied distinct environmental settings along a climatic gradient of increasing precipitation and elevation. At relatively dry PIPO sites understories were dominated by ponderosa pine. At wetter PIPO/PSME and PIPO ABGC sites understories were dominated by shade tolerant species, but ponderosa pine was dominant in the overstory. At the coolest and wettest PIPO/PSME/ABGC sites understories were dominated by grand fir and shade tolerant species were common in the overstory. In the eastern Cascades current density of all live trees and snags was 432, 461, 570, 372 trees per hectare (TPH) for the four stand types identified. Stand types in the drier Ochoco Mountains were currently less dense at 279, 304, 212, and 307 TPH. Current MCF densities in both areas are 2-3 times higher than densities estimated for the late 19th and early 20th centuries from other studies in those two areas. Reconstruction of cuts in each stand type indicates that the density of large diameter ponderosa pine has been reduced by approximately 50% in all stand types in both study regions. Age histograms demonstrate that current density and composition of MCF stand types is a product of abrupt increases in tree establishment following fire exclusion in the late 19th century. The number of trees established increased after 1900 in all stand types, but the timing and composition of changes in establishment varied with climate. At dry PIPO sites increases in establishment were delayed until the 1920s and 1930s and were composed of ponderosa pine. At PIPO/PSME and PIPO/ABGC sites with intermediate precipitation, establishment was dominated by ponderosa pine prior to 1900, but after 1900 establishment was dominated by a large pulse of Douglas-fir and grand fir. At the wettest PIPO/PSME/ABGC there was less evidence of changes in structure and composition over time. My results indicate that compared to dry pine and dry-mixed conifer sites, relatively productive moist mixed-conifer sites were characterized by large changes in structure and composition. Such sites could be considered more ecologically altered by lack of fire than drier forest types that had high fire frequencies but slower rates of stand development and less plant community change. Radial growth patterns of cored ponderosa pines differed between the eastern Cascades and Ochoco Mountains. In the eastern Cascades mean growth rates and variance decreased during favorable climatic periods after 1900. This is likely related to increased competition, and provides evidence that current stand density lacks a temporal analog in the 18th and 19th centuries. Sensitivity of growth to climate and harvest suggest competition for water in the denser forest of the eastern Cascades, and indicates thinning will increase the diameter growth rate of large old pines. In the Ochoco Mountains, ponderosa pine tree growth was less responsive to climate prior to fire exclusion in the late 1800s, and growth did not respond to fire events. This suggests competition among trees was historically low in this region. After fire exclusion growth became more responsive to wet and dry climatic cycles, which may indicate that increased density and competition made trees more responsive to climate variability. Patterns of slow and fast growth appeared to differ between study regions and likely differ at the sub-regional scale. Further analysis of the relationship between growth and climate in different environmental settings is needed to distinguish where stand development has been modified by disruption of fire regimes. / Graduation date: 2013

In the Pacific Northwest (PNW), concern about the impacts of climate and land cover change on water resources, flood-generating processes, and ecosystem dynamics emphasize the need for a mechanistic understanding of the interactions between forest canopies and hydrological processes. A detailed measurement and modeling program during the 1999 and 2000 hydrologic years characterized hydrological conditions and processes in a 500-600 year old Douglas fir-western hemlock seasonal temperate rainforest. The measurement program included sub-canopy arrays of radiometers, tipping bucket rain gauges, and soil temperature and moisture probes, to supplement a vertical temperature and humidity profile within the forest canopy. Analysis of the precipitation interception characteristics of the canopy indicated that the mean direct throughfall proportion was 0.36, and the mean saturation storage was 3.3 mm. Evaporation from small storms insufficient to saturate the canopy comprised 19% of the net interception loss, and canopy drying and evaporation during rainfall accounted for 47% and 33% of the net loss, respectively. Results of the measurement program were used to modify the Simultaneous Heat and Water (SHAW) model for forested systems. Changes to the model include improved representation of interception dynamics, stomatal conductance, and within-canopy energy transfer processes. The model effectively simulated canopy air and vapor density profiles, snowcover processes, throughfall, soil water content profiles, shallow soil temperatures, and transpiration fluxes for both a calibration period and for an uncalibrated year. Soil warming at bare locations was delayed until most of the snowcover ablated due to the large heat sink associated with the residual snow patches. During the summer, simulated evapotranspiration decreased from a maximum monthly mean of 2.17 mm day����� in July to 1.34 mm day����� in September, as a result of declining soil moisture and net radiation. Our results indicate that a relatively simple parameterization of the SHAW model for the vegetation canopy can accurately simulate seasonal hydrologic fluxes in this environment. Application and validation of the model in other forest systems will establish similarities and differences in the interactions of vegetation and hydrology, and assess the sensitivity of other systems to natural and anthropogenic perturbations. / Graduation date: 2002