Search

The fundamental question of this thesis addresses the suitability of spatial point processes for the modelling of plant communities with the aim of understanding the mechanisms that sustain biodiversity and allow species coexistence through an analysis of a biodiverse plant community in Western Australia. Terrestrial plants are non-motile organisms and hence interact mainly with their nearest neighbours. Therefore, plant community dynamics need to be modelled in a spatial context. Spatial point process models describe the arrangement of objects in space and derive information on inter- and intra-species interaction through an analysis of the objects’ relative position. However, there has been a lack in appropriate methodology since previous applications of spatial point processes have analysed data sets of much smaller complexity and research has been mainly theory driven. This thesis develops new methodology suitable for this context. It provides parsimonious tools for the exploratory data analysis and derives multivariate methods for spatial point pattern data for the first time. In addition, three models of increasing complexity are fitted to the data and their suitability is assessed. This thesis has provided a number of statistical tools that may also be successfully applied in other situations, notably where highly multivariate data sets of spatial patterns occur. The methods are suitable in the context of plant community dynamics and their application to the study data set has made contributions to the development and validation of existing ecological theories on biodiversity. Furthermore, they informed specifically on intra- and inter-species interaction structures in the study data set and are ultimately contributing to conservation.

Picea sitchensis is an important tree species for UK forestry and is at the forefront of prototype clonal breeding programs. These can only be implemented using in vitro, culture therefore cryopreservation technology development is imperative such that elite germplasm can be conserved, without compromise to genetic integrity, whilst phenotypic validation of selected genotypes is undertaken. Three explant types were transferred from the Northern Research station, Roslin to the University of Abertay, Dundee where cryopreservation testing was initiated. Each explant comprised of different anatomical complexities varying from the simplest dedifferentiated embryogenic suspensor masses, to matured somatic embryos and whole tissue shoot-tip apices. Before cryopreservation was initiated in vitro cultures were stabilised and characterised at UAD. Shoot cultures showed different growth responses between genotypes and between culture locations, but biochemical profiling of oxidative stress markers, ethylene and DNA methylation did not confirm stress or epigenetic change as the cause of these differences and physiological recalcitrance. A cryopreservation protocol, using a programmable freezer (Planar), was successfully developed and is reported for the first time for P. sitchensis embryogenic suspensor masses (ESM). Post-LN survival rates of up to 100% were observed in several genotypes. Encapsulation-dehydration was successfully utilised to cryopreserve P. sitchensis mature somatic embryos reported for the first time. Recovered embryos were able to re-initiate into dedifferentiated non-embryogenic masses (NEM) (up to 100%) and embryogenic suspensor masses (ESM) (up to 20% post -LN) as a source of material to mass multiply cryopreserved clonal offspring. Major steps were progressed for the most recalcitrant conifer explant in the project, shoot-tip apices, with essential pre-treatment steps established. Critical cryogenic factors were determined through thermal analysis using Differential Scanning Calorimetry. The study concluded with the initiation of technology transfer of cryopreservation methods to the Northern Research Station to establish the UK’s first conifer cryobank. These systems were preliminary validated. Further implementation will proceed out with the timescale of this project but based on recommendations generated from this thesis.