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Floodplain woodlands are valuable environments, providing a diverse habitat for many riparian and land-based species. It is now recognised that the continual loss of floodplain woodland has impoverished the national biodiversity of riparian environments, and measures have been brought in both nationally and through the European Commission to halt the decline. This has however, highlighted a deficiency that has existed for many years in the field of river hydraulics. The representation of complex riparian vegetation environments within river models remains an area not adequately addressed. This research presents experimental investigations into floodplain woodland vegetation, with a view to improving the representation of these vegetations within numerical models. Floodplain woodland hydrodynamics were explored with scaled-down (1:8) stag gered arrays of single stem and multi-stem model trees at planting densities of 8.8, 19.8 and 80.6 plants per m 2. The planting densities investigated correspond to the recommended planting densities cited by the Forestry Commission UK. Roughness factors, including Manning's n, the Darcy-Weisbach friction factor / and the bulk drag coefficient Ca were computed for the different model tree and planting density combinations. Velocity measurements within the arrays were investigated, and a study to determine the optimum sampling strategy was carried out to obtain representative velocity and turbulent kinetic energy measurements within the model tree arrays. The optimum sampling locations for streamwise velocity appeared to be clustered around 0.3 s and 0.7 s, where s is the lateral or longitudinal spacing between the model trees, while for turbulent kinetic energy the optimum location was 0.5 s. Full scale drag force versus velocity tests of floodplain woodland trees were carried out and a drag area parameter CdA.Uo derived. The trees experienced little to no bending at low velocities, with force varying linearly with the square of velocity, while considerable deflection was observed at higher velocities, with force varying linearly with the velocity. Physical parameters including height, diameter, mass and volume of the wood are compared against the drag area parameter, with mass and volume showing a stronger correlation than height or diameter. The increase in the drag area parameter due to the presence of foliage was also investigated. The numerical incorporation of floodplain woodland vegetation is presented with respect to two-dimensional depth-averaged numerical modelling. A reach of the River Laver in North Yorkshire, England was modelled to assess the hydraulic impact of the conversion of arable land to floodplain woodland.

An emerging theme in global climate modelling is whether land covers created in the clearance of tropical humid forests influence water exchange between remnant forest patches and the atmosphere, and, if so, how this affects regional and global water exchange. Fieldwork presented in this thesis ascertains whether the amount of water transferred to the atmosphere from a humid tropical forest situated in Sabah, Northern Borneo, Malaysia, differs between its edge and interior due to the influence of surrounding clearings through horizontal heat transfer. Using satellite imagery to measure the shape and size of tropical forests, field measurements of water transfer were extrapolated to continental and global levels to infer how differences in water exchange with the atmosphere between forest edges and interiors may influence regional and global forest-atmosphere water exchange. Mean sap flow in trees within 50 meters of a forest-clearing boundary was found to be 73% greater than that in trees further into the forest; an observation supported by the decreased canopy temperature also recorded there. Evaporation from the forest canopy constituted a high fraction of annual rainfall (33%), but showed no edge effect similar to that of sap flow. Edge plots, however, expressed evapotranspiration rates 22% lower than forest interiors (657-890 mm yr-1), owing to the lower number and size of trees there. One edge plot, however, exhibited evapotranspiration 49.5% greater than that of forest interiors. Gradients of air temperature, vapour pressure deficit and wind speed from the adjacent clearing to the forest interior indicated that warm, dry air moving from the clearing to the forest was the most credible cause of increased sap flow of trees near the forest edge. This hypothesis was supported by a strong correlation between the amount of vapour in the air moving from the clearing and tree water use. It was estimated that the influence of differences in water transfer to the atmosphere between the edges and interiors of tropical forest would not alter global water transfer to the atmosphere by more than 0.25-4%, or by 4-7% in the most fragmented tropical continent, Africa. However, it remains unclear whether the inclusion of tropical forest edge effects within climate models is necessary, as the pioneering nature of this thesis, and of existing studies reviewed within it, means that solid conclusions will be dependent upon future work. This thesis concludes with suggestions for future research that will most effectively consolidate the provisional conclusions and recommendations herein.

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The tropical high forests of West Africa have been under stress due to a greater dependence on wood resources. Logging rate has more than doubled within the last decade. However, the exact effects of logging on vegetation composition and the degree of canopy opening that should be created in the forest to ensure the regeneration of timber tree species are not known. Three major experiments were carried out to determine the ecophysiological responses of timber tree species in different irradiances and red:far-red ratios. (1) 16 tree species were grown in six neutral shade treatments (2, 6, 27, 42 and 65% full sun) and their growth assessed by standard measurements used in growth analysis (biomass, height, stem diameter, leaf area, leaf production and mortality). (2) Eight species, of which six were also used in the shade house experiment, were grown in a series of artificially-created gaps in two forest sites differing in annual rainfall. Gaps created received 1-2, 5, 10, 15, 30 and 66% full sun. (3) Possible differences in the results between shade house and forest experiments due to differences in light quality (red:far-red ratio) were tested separately. Differences in red:far-red ratio has little effect of growth but showed some influence on allocation of biomass. Seedling growth response of species were higher in shade houses compared to the two field sites and higher in the wet compared to dry forests. Sixteen tropical timber tree species were ranked on an ecological (shade tolerance) gradient based on their differential growth response to light. The results indicate that the ranking of species on an ecological gradient is robust and potentially more reliable than intuitive classification of species into groups.

This is a study of methods whereby decisions on thinning and felling forest stands can be made relevant to the primary objective of a forest enterprise. Various investment criteria are considered and guidelines on the criterion that should be applied to a given situation in forestry are given. Maximising the present worth of an estate is taken as the most suitable financial objective for most forestry enterprises in Britain. A method is produced to estimate the most appropriate discount rate to use taking into account both death duty risks and diversification of the total investment portfolio; and a model is developed to simulate the effect of different management decisions on the value of the investment criterion. Several methods of maximising the investment are considered and an integer programming solution is used in an attempt to choose near optimal management decisions.

The purpose of the present study was to extend the principles and methods developed in Strathdon over a wider area. It was decided to work with Sitka spruce at twelve forests in north-east Scotland, restricting sites to areas of at least 0.5 ha free of check in closed canopy stands of Queen Charlotte Island provenance. The project was planned in four stages:- (i) to determine and evaluate the more influential site factors affecting Sitka growth and to derive yield prediction equations from the regression analysis of sample plot data. (ii) to test the accuracy of these equations and their suitability as a, method of forest capability assessment (iii) to investigate and compare an alternative physiographic approach to forest capability assessment. (iv) to produce forest capability maps amplified by forest notes which would include descriptions of important factor effects and their implications for management. Seventy three temporary sample plots were randomly selected within suitable stands to cover as wide a range of sites as possible within the study area, and site factor and tree growth data were collected from each plot. Correlations multiple regression and factor analyses were then carried out on this data and yield prediction equations produced. In assessing yield, allowance was made for the ubiquitous presence of initial check by using the growth rate after check deduced from age/height curves of felled trees. The sample plots were grouped into three nuclei (each containing several forests) and four elevation classes to investigate the variation of site/growth relationships and to determine the size of areas for which, simple yield equations of adequate predictive ability could be derived. In the second field season a further fifty four sample plots were randomly selected in the six main forests to test the predictive ability of the above equations. An investigation into the-variability of soil factors and tree growth was also carried out, for sample plots ranging from 0.01 to 1.00 hectare, because an unexpectedly poor relationship was found between Sitka growth and the level of extractable nutrients. The site factors most significantly correlated with Sitka yield were total nitrogen and phosphorus in the organic horizon, geomorphic shelter, elevation, position-on-slope, winter (and annual) rainfall and the mean accumulated soil (and air) temperature in the growing season. The adverse effect of poor- soil drainage is more important at sites where meteorological factors are not limiting, and Sitka growth is significantly poorer on soils derived from ultrabasic parent materials and hornblende schist.

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No description available.

The objective of this study was to develop refined procedures for the economic analysis of stand treatments for timber production. This objective has been achieved by a review and explicit statement of the economic principles relevant to the analysis of stand treatments. Based on these principles, procedures for the analysis of silvicultural investments are proposed and demonstrated. The review of economic principles indicated that the appropriate class of criteria for the analysis of stand treatments are expected Present Certainty Equivalent Value. However, these criteria were also shown to be incomplete due to the failure of the Separation Theorem to hold under imperfect markets. This incompleteness and the theoretical requirement that the quantity and price of inputs and outputs, of investment ensembles, be measurable limits these criteria to defining efficient investment emsembles. Although these criteria were found to be incomplete, they do provide a means of organizing the measurable information associated with alternative stand treatments in a way that contributes to the selection of an optimum combination. The review also points out the necessity of correctly identifying the opportunities for productive transformation in the analysis of investments. In addition, the requirement to estimate real prices, which define exchange opportunities in a manner consistent with the concepts of intertemporal choice is identified. The maximization of expected Present Certainty-Equivalent Value of wealth gain is proposed as the rule and criterion for the economic analysis of stand treatments. The elements of the analysis procedure relating to (1) the level of analysis, (2) its duration, (3) the interval within the analysis period, and (4) treatment possibilities considered are discussed and a standard for each proposed. In addition, the requirements for estimates and measurements of the quantity and price of inputs and outputs are discussed. Standards for these estimates and measurements are identified in three categories; the requirements for the calculation of expected Present Certainty-Equivalent Value of wealth gain, the timber management requirement, and the measurement requirements. The procedures for the analysis of stand treatments are demonstrated for a hypothetical compartment of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in western Washington. The treatments considered in the analysis include thinning, fertilization, and regeneration. The conclusion of the study is that the procedures proposed and demonstrated are feasible and practical under current conditions. Further, the information resulting from these analyses will contribute to a more efficient allocation of resources in timber production. Additional study of the economic theory of investment choice is recommended with particular attention being concentrated on the theory of exchange in imperfect markets, and the role of information in the selection of uncertain alternatives. However, the major opportunity for additional study is in the collection of information and the development of estimation techniques required to forecast the quantity and price of inputs and outputs associated with investments in timber production.