Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003. / Thesis documentation sheet inserted. Appendix reprints five papers and manuscripts co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.

Spatial competition indices for Scots pine and birch growing in heterogeneous Caledonian forest in Glen Affric were developed. Competition indices (CIs) have frequently been used in empirical models of individual tree growth. However, the contribution of CIs to the predictive ability of growth models is often very small. The poor performance of CIs may relate to the choice of spatial descriptors and functional form of the index. To improve CI performance a novel approach utilising neural networks and simulated annealing for the optimisation of CIs was developed.

Scots pine (Pinus sylvestris L.) represents around 16% of the area of commercial conifer plantations in Great Britain, but around 30% in north and north-eastern Scotland. Most of the timber produced from these forests goes into lower-value markets such as fencing and panel products, and only a small proportion is converted into high-value structural timber. In order to maximise financial returns from this resource in the medium and long term, it will be necessary to increase the outturn of structural timber. However, this requires knowledge of the variation in those wood properties that influence structural timber performance and of the effects of silviculture on wood quality. Changes in silvicultural practices in recent decades—wider initial spacings, a preference for artificial regeneration, and an increased use of mechanised thinnings, have led to concerns about the suitability of Scots pine timber for use in structural applications due to potentially poorer stem form, a greater proportion of juvenile wood and larger, more numerous knots. As part of the research presented here, novel predictive equations were developed for the key physical, mechanical and branching properties that determine structural timber quality in Scots pine, namely: microfibril angle, wood density, clearwood bending strength and stiffness, and branch number, size, insertion angle and status (alive or dead). Simulations were carried out using these equations to examine the effects of different silvicultural regimes on each wood and branch property of interest. Based on these simulations it is recommended that in order to produce high quality Scots pine timber, trees are planted at narrower initial spacings and grown on longer rotations than currently prescribed, and, where appropriate, thinnings should be delayed. Together, these measures will restrict final branch size and the amount of mechanically inferior juvenile wood in the final crop.

No description available.

Inaug.-Diss.--Giessen. / Lebenslauf.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005. / Appendix includes papers co-authored with others. Includes bibliographical references. Issued also electronically via World Wide Web in PDF format; online version lacks appendix.

Thesis (Ph.D.)--Aberdeen University, 2007. / Title from web page (viewed on Mar. 2, 2009). Includes bibliographical references.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003. / Thesis documentation sheet inserted. Appendix includes reprints of five papers and manuscripts, four co-authored with others. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix.

No description available.

Clean laboratory technology and pure culture techniques were combined to determine the effect of ectomycorrhizae on the uptake of lead by Pinus sylvestris L. seedlings. By culturing the ectomycorrhizal fungus, Pisolithus tinctorius (Pers.) Coker and Couch, in liquid Hagem's medium with different concentrations of lead (0, 50, 250 and 500 ng/g sol), it was determined that the fungus readily takes up lead from such and aqueous medium. It was also determined that the pH of the medium controls the amount of lead in solution that can be taken up by the fungus. A series of growth studies where Pisolithus was cultured on Hagem's agar indicated that the growth of the fungus is reduced when the lead concentration in the medium is approximately 25 ug/g sol. It was estimated that a lead concentration of approximately 1,000 ug/g sol may completely inhibit the growth of the fungus. Furthermore, it was determined that the acetate ion is inhibitory to the growth of Pisolithus. By culturing mycorrhizal and non-mycorrhizal seedlings of P. sylvestris and analyzing the seedlings' roots, stems and leaves for their lead concentrations, it was determined that ectomycorrhizae facilitate the uptake of lead. Ectomycorrhizal roots can take up more lead from a vermiculite/hydroponic solution mixture because of their greater surface area and exploration of vermiculite surfaces as well as their increased production of lead solubilizing acids. This additional lead found in mycorrhizal roots, however, does not appear to be translocated to the above ground portions of the seedlings. This increased uptake of lead by mycorrhizal roots is expected to take place in natural soil systems as well. / Master of Science