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Weights and growth rates, feeding ecology, population ecology and social and spatial organisation of feral goats in the Southern Uplands of Scotland were investigated between 1977 and 1980. Seven populations were described as to their origins, breed type and management. In general, goats in the eastern populations were significantly larger than those in the western populations; those in the central populations were usually intermediate in size. This variation was probably related to variations in range quality.. Observations and faecal analyses showed that the feeding ecologies of goats and hill sheep, a potential competitor, were similar. In general, sheep used freely drained grasslands more and ate proportionately more grass than goats; the latter, possibly as a result of competition, ate more ferns, conifers, rica and rushes than the former. The very heavy use of ferns (bracken) by goats was discussed in relation to previous studies. Population size varied between c. 500 and c. 15 depending partly on the degree of culling. Billies, in general, had lower survival rates than nannies and together with kids their numbers varied within populations more than those of nannies. Reasons for the sex differential in survival and the variability in kid production were discussed in relation to reproductive behaviour, climate and population regulation. Group size varied in a predictable fashion with season, group type and population size. Complete sexual segregation did not occur but older billies tended to associate least with nannies, and especially so in the spring. Goats were spatially organised into hefts i. e. groups of individuals having highly overlapping home ranges; in general there was little overlap between heft home ranges and only billies moved between hefts and then predominantly at the rut. The ecology of feral goats was compared with that of other species with particular reference to the questions of dispersal and territoriality. Recommendations for improved management and future research concluded the thesis.

This programme of research examines the ecology of the threatened perennial Lobelia urens L. (the heath lobelia) which reaches the northern limit of its distribution in the southern coastal counties of England. A survey of the historical evidence of the distribution of the species in England is presented. Restricted to such a small area, L. urens has always been rare in Britain. The six remaining populations were surveyed to describe the phytosociology of communities containing L. urens and the variability of the environmental factors controlling its distribution. L. urens is shown to be a member of rough grass-heath communities dominated by Molinia caentlea and situated on seasonally waterlogged, moderately acidic, nutrient-poor soils. Studies of the demography of L. urens focused on two extant populations. Experimental research was carried out to support these demographic studies both in the field, on plants grown in a common garden, and under the controlled conditions of the glasshouse and laboratory. This information on the ecology of L. urens was used to construct stage-structured population in atrices. Recruitment success in L.urens is shown to be very low in Britain and results suggest that this controls the density of British populations. The availability of seed does not regulate the rate of germination. Instead, recruitment of L. urens at the northern edge of its range is restricted by its specific habitat requirements, along with low summer temperatures and the short growing season. Establishment from seed is facilitated by micro-habitats that provide high light intensities and, more importantly, protection against soil moisture loss. Whilst winter disturbance by herbivores is shown to be essential for successful recruitment, adult growth and survival is better in ungrazed communities. However, even the small plants of the grazed areas are very fecund. The seed forms a large persistent bank that embodies a reserve of individuals and genetic variability which offers protection against extinction. The thesis concludes that the soil moisture status and disturbance regimes at Redlake and Andrew's Wood are limiting the growth rates of the L. urens populations. In order to maintain populations, the redirection of drainage water is prescribed to increase the soil moisture status. L. urens is suited to intermittent soil disturbance, the timing and intensity of which was shown to be important, whilst the duration between grazes was seen to be less critical. Results suggest that the habitat created by occasional heavy winter grazing of fattening cattle would be very favourable to L. urens.

The distribution of suspended algae was investigated in a 69-km length of a small lowland river in the UK, the Nene (annual median discharge at km 91.7 =6 m(^3) s(^-1). Variations in chlorophyll a data collected between 1975 and 1998 by water management organisations at km 91.7 were evaluated against a range of physical and chemical variables. Interpretation was aided by additional sampling between 1993 and 1997.The latter half of the 24-year period had significantly higher temperatures and sunshine-hours and significantly lower ammonium concentrations. Discharge, temperature and sunshine-hours were significant predictors of chlorophyll concentration, particularly between January and June, and spring chlorophyll maxima ranged from 106 to 276 µg L(^-1).Centric diatoms were the most abundant taxa in the main-river and, in the absence of other limiting factors, appeared to be restricted by the availability of silica. There was also evidence that the centric diatoms suffered from severe parasitism. Inter-year phytoplankton abundance was most variable in the summer, and years with abundant submerged macrophytes had particularly low phytoplankton numbers. Spring phytoplankton peaks occurred earlier and had smaller amplitude at downstream sites than those further upstream. Average spring chlorophyll concentrations (April - June) increased significantly between km 22.4 and km 43.9, thereafter remaining high to km 91.7. Spatial trends were attributed to changes in channel morphology, retention time, dead zones, longitudinal variations in current velocity, temperature and silica limitation. An appraisal of the Utermöhl method of counting phytoplankton was made and a new technique proposed, called 'spaced fields'. The spaced fields method accurately identified small changes in phytoplankton abundance and was used to identify short-term temporal and small-scale spatial trends in the Nene.

Background information, essential to a full appreciation of the research presented in the thesis, is submitted in Chapters Two, Three and Four in the form of literature reviews. Chapter Two includes a review of the geology, climate, soils, past management, vegetation history and nature conservation value of Bodmin Moor. The chapter culminates by discussing the proposed future management of grazing on Bodmin Moor. Chapter Three comprises a review of the mechanisms by which grazing affect vegetation. Particular reference is made to the effects of 7 General Introduction variation in grazing practices and interactions between grazing and other environmental variables. Chapter Four provides a review of successional processes with particular reference to the effects of grazing on upland plant community succession and the limits of current knowledge of grazing management in upland habitats. Chapter Five presents the results of phytosociological classification and explores the relationships between environmental variables and vegetation. Chapter Six examines spatial variation in the seed bank of Bodmin Moor in a range of communities at different depths. Chapter Seven presents the results of a Countryside Stewardship monitoring scheme established on Bodmin Moor North SSSI. Chapter Eight investigates the effects of variation in timing, frequency and severity of defoliation, on Molütia caerulea, along a soil moisture gradient. Chapter Nine reviews the preceeding work focusing on the overall implications of the thesis. The structure of the thesis is presented diagrammatically in Figure 1.1.

The cystophorous hemiurid cercariae, Cercaria vaullegeardi and C. calliostomae, are recorded from the digestive gland of Gibbula umbilicalis and the gonad of 'Calliostoma ziziphirtum respectively. The encysted forms are described at ultrastructural level for the first time, and developmental stages redescribed. Specialisation of the anterior region and birth pore of the daughter sporocyst in C. vaullegeardi, and migration of the redia in C. calliostomae, ensure that in neither species does the cercaria, hindered by a bulky immotile cystophorous tail, itself have to migrate through blood vessels or tissues to the site of emergence from the molluscan host. The inoculative mechanism whereby hemiurid cercariae infect the copepod second intermediate host is described for the first time in C. vaullegeardi. Experimental infections of the harpacticoid copepod Tigriopus brevicornis are recorded, and the infection process is related to the ultrastructure of the cercaria and to the feeding mechanics of harpacticoids. The cystophorous tail of C. vaullegeardi is shown to be a device whose shape and construction ensure that the cercarial body is neither damaged by copepod mouthparts nor swallowed, but reaches the host haemocoel during the initial stages of feeding. The metacercaria grows rapidly within T. brevicornis, virtually filling the haemocoel 21 days after infection when maintained at 17°C. The development of the ecsoma from the eversible excretory vesicle is described. Post-larval Gcbius paganellus have been experimentally infected by feeding 21 day-old metacercariae of C. vaullege ardi raised in T. 'brevicornis. Encapsulated metacercariae and adults are recorded from 7 out of 12 species of fish examined for natural hemiuroid infections. The function of the hemiurid ecsoma is discussed in relation both to habitat of the adult within the host pyloric stomach, and to ultrastructural and autoradiographic studies of metacercarial and adult stages.

Large-scale rhizome sampling on the North York Moors together with an assessment of published bracken sampling protocols concluded that small-scale sampling of the rhizome system is inadequate to describe upland bracken stands accurately. It is also concluded that the frond cannot be used as an indicator of the rhizome system before or after treatment to achieve bracken control. An improved sampling strategy is proposed which increases the reliability of data collected and the validity of any conclusions drawn form such data. The structure of bracken rhizome systems, from separate stands on the North York Moors, were found to be distinct from one another and demonstrated intrinsic variation which could affect a differential response to control. The most important components of the rhizome system, when considering chemical control using asulam are: the number of buds likely to remain viable afterwards: the rhizome biomass which may effect herbicide dilution: and the origin of frond production which may affect herbicide distribution. The effect of asulam was to cause severe localised damage to buds and apices detectable one year after treatment but the rhizome dry weight remained unaffected. In one instance asulam appeared to have a stimulatory effect on bracken by breaking bud dormancy, this was related to the characteristics of the stand before treatment. It is recommended that the use of asulam is restricted to pioneer or building stands which have a high number of active buds in relation to dormant buds. and a low rhizome dry weight. Crushing bracken once a year effected a temporary reduction in rhizome dry weight and an increase in frond number (which could improve asulam absorption). A combination of crushing and asulam reduced both bud number and rhizome dry weight and was thus the most successful treatment studied for reduction of bracken vigour. In particular. stands adjacent to valued plant communities should be targeted for control. It is suggested that bilberry could be used as a buffer zone between heather and invading bracken. The use of large-scale bracken control programmes in upland regions was questioned due to the apparent ineffectiveness of asulam on the rhizome system. and the difficulty of implementing a programme of successful follow-up and after-care management. A broad clarification of upland bracken, based on the rhizome, was recognised, and general models of selective bracken control suggested, by evaluation of the rhizome system with regard to the number of dormant and active buds, and the rhizome dry weight.