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No description available.

<i>Peridermium pini</i> causes a stem rust of two-needled pine trees, with the greatest problems in the United Kingdom associated with Scots pine forests in north-east Scotland.  It was hypothesised that silvicultural practices are viable options for controlling the incidence of <i>P. pini </i>and that a combination of climatic and biophysical factors may be significant in regulating the incidence of the disease.  <i>P. pini </i>incidence was determined in four Scots pine plantations established in Moray, and in five native pinewoods.  <i>P. pini </i>incidence in the Scots pine forests of north-east Scotland has increased since the previous surveys undertaken in the 1960s.  Mean disease incidence for all plantations was 4.9%, with a range from 4.0% at Cawdor Estate to 5.7% at Darnaway Estate. Age-class, the number of years since thinning, elevation and continentality were statistically significant factors influencing disease incidence.  These factors were used as the basis for a rule-based model to describe the distribution of <i>P. pini </i>within the forests surveyed. A second modelling approach, using Bayesian methods to analyse a large number of datasets, supported the hypothesis that management factors had the major influence on incidence of the disease and that climatic factors added, incrementally, to explaining the spatial distribution of the disease.  Maps produced from the outputs designated the probabilities of <i>P. pini </i>incidence into risk classes. Estimation of timber volume losses in infected stands confirmed that the disease would have significant economic impact in most sites if no savage thinnings were undertaken.  This process would have the most significant effect at Altyre Estate. The combination of these modelling approaches with Geographic Information Systems is potentially useful as a decision-support tool for forest managers, enabling greater confidence in judging the potential local significance of the factors affecting disease incidence.

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Classical dendrochronology involves using standard statistical methods, such as correlation coefficients and t-values to crossmatch undated tree-ring width sequences to dated 'master' chronologies. This crossmatching process aims to identify the 'best' offset between the dated and undated sequences with a view to providing a calendar date estimate for the undated trees. Motivated by the successful and routine use of Bayesian statistical methods to provide a fully probabilistic approach to radiocarbon dating, this thesis investigates the practicality of using a process-based forward model known as 'VSLite' at the core of Bayesian dendrochronology. The mechanistic VSLite model has the potential to capture key characteristics of the complex system that links climate to tree-ring formation. It allows simulated, dated tree-ring chronologies to be generated at any geographical location where historical climate records exist. Embedding VSLite within a Bayesian approach to tree-ring dating allows combination of both ring-width data and any available prior information. Additionally, instead of identifying the `best' calendar date estimate, the Bayesian approach allows provision of probabilistic statements about a collection of possible dates, each with a specific (posterior) probability. The impact of uncertainty in the VSLite input parameters on the model output has been systematically investigated in this thesis, and the VSLite-based approach to Bayesian tree-ring dating has been explored using both simulated and real data. Results of implementing the new VSLite-based approach are compared with those using current classical and Bayesian approaches. An option for reducing the need for preprocessing data is also investigated via a data-adaptive rescaling approach. Having established the effectiveness of using the mechanistic forward model as the core for Bayesian dendrochronology, the practicality of adopting it to aid in dating in the absence of suitable local master chronologies is also explored.

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No description available.

No description available.

The limited range of commercial timber species in Great Britain has led the forestry sector to consider wider planting of other species. This research addresses wood properties, particularly relevant to structural timber, of noble fir, Norway spruce, western red cedar and western hemlock in Great Britain. Sampling covered three regions to get a representative sample for the country. Bending stiffness, bending strength, density and twist distortion from drying were assessed. The results showed high yields of C16 for all these species, with Norway spruce and western hemlock performing comparatively well to typical British-grown Sitka spruce. Within this dataset, variation of mechanical properties within trees was more important than differences between species. Strength and stiffness increased with age, whereas density followed different trends in the inner and outerwood. The three properties were modelled based on ring number. The use of acoustic techniques to assess the mechanical properties of wood (in particular stiffness), was investigated in clears, sawn timber, logs and trees. The best results were found combining density with acoustic velocity in sawn timber. The use of acoustic techniques in standing trees was more reliable measuring distances of two or three metres, rather than the commonly used one metre; most likely due to a change in the wave propagation. Tree architecture was studied for timber production and quality. Noble fir described the highest merchantable taper profile. Branchiness varied importantly with height in the stem, and models were built for number, diameter and angle of branches. Western red cedar and western hemlock had fewer but thicker branches compared to noble fir and Norway spruce. Future work should produce grading machine settings and address the variation of timber quality and merchantability under different silvicultural regimes. This thesis concludes that the four species investigated can contribute to diversity the timber industry in Great Britain.

The tropics are a key part of the global biosphere. Specifically, the woodland environments not only moderate large scale climate dynamics, but are also crucial in the global carbon cycle. Despite this, tropical dendrochronological studies are rare due to the uncertainty in annual dating from the minimal seasonality in most tropic environments. Without distinct annual tree rings, dendrochronological dating methods do not work, therefore other dating methods are required before long term forest growth analyses can be made. Alternatives such as radiocarbon and stable isotope measurements can be expensive and require high resolution measurement in order to identify seasonality. This thesis introduces a novel dating method for tropical trees using calcium as a tracer of annual wood formation. Laser Ablation-ICP-MS provides a fast, high resolution method for measuring mineral elements which could potentially provide a solution to the dating of tropical trees. Initially, Scots pine provided an excellent testing species for the development of both the methodological and analytical dating methods proposed through this thesis. It's well defined, annually dated ring structure formed the basis of seasonal signal detection and the development of an objective analysis for dating. This was achieved by the continuous measurement of calcium, and utilising a threshold detection approach to define annual growth cycles with respect to extreme peaks in the tracer data-series. The initial success of the calcium dating method using pine allowed for testing the technique on a tropical trees species from Cameroon which lacks distinct rings. Along with radiocarbon dating, the robustness of the calcium dating method for this tropical species was assessed. Promising results were initially found however, these could not be replicated and validation of this method proved problematic. Finally, radiocarbon dates were used to assess the nature of the oxygen and carbon stable isotopic series from the single tree of the same species from the tropical calcium tests. Results showed that despite the clear cyclic signal present in the oxygen isotope record, this did not represent an annual signal. These results reinforce the problems associated with tropical dendro analysis.