• Colonisation and development of salt mark in the Dee estuary, NW England: Integrating large-scale pattern and small-scale ecological process

      Marrs, Robert H.; Potter, Jacqueline; Huckle, Jonathan M. (University of Liverpool (Chester College of Higher Education), 2000-07)
      The Dee estuary, one of the most important British estuaries in terms of size and conservation value, has been subject to extensive colonisation and development of intertidal mudflats by salt marsh vegetation. In the last century, acceleration of this process has been attributed to the ability of Spartina anglica C.E. Hubbard to colonise bare sediment. The research in this thesis aims to investigate the ecological patterns and processes involved in the development of salt marsh vegetation. These have been examined using a large-scale approach involving remote sensing techniques and a small-scale approach to examine ecological processes at the level of the individual plant and species. Large-scale temporal patterns in the distribution were investigated by analysing a sequence of monochrome aerial photographs dating from 1955 to 1997. At the marsh apex, initial rapid colonisation was followed by a decreased rate of expansion and a reduction in the pioneer zone. This suggested a steepening of the marsh elevation gradient, which is interpreted as the marsh approaching its natural limit of expansion. The rate of salt marsh expansion was consistent across the time sequence for the second target area, a cross-section of the marsh gradient, but with S. a«g/zca-dominated colonisation of mudflats changing to colonisation by a pioneer community co-dominated by S. anglica and Salicornia europaea. Large-scale spatial distribution patterns were further investigated using multispectral remote sensing data from 1997. Radiometric data were used to define the spectral characteristics of the major types of salt marsh vegetation. Airborne Thematic Mapper data were used to classify the reflectance data from the whole marsh to determine the spatial distribution of plant communities based on their spectral characteristics. Mapping of these communities provided a baseline that will be a useful tool for future management of the salt marsh. An experimental approach was used to examine the role of abiotic and biotic factors on the growth and interactions between S. anglica and Puccinellia maritima (Huds.) Parl. In two series of competition experiments, P. maritima exerted a one¬way effect over S. anglica. The intensity of this interaction was increased in environmental conditions favourable to P. maritima, and was greater in terms of above-ground than below-ground biomass. In both experiments, S. anglica exhibited a disproportionate reduction in below-ground competitive interaction in abiotic conditions less favourable to P. maritima. A corresponding increase in rhizomes suggested that this is a potential mechanism by which S. anglica may evade competitive neighbours at low marsh elevations. An appreciation of the importance of scale has led to a multi-scaled and holistic view of the ecological process of salt marsh colonisation and development. Integration of both large and small-scale approaches has provided valuable information on the ecological patterns and processes, and has important implications for current and future management of salt marsh in the Dee estuary.
    • Physiological and behavioural measures of stress in domestic horses

      Young, Tamsin (University of Liverpool (Chester College of Higher Education), 2011-09)
      The welfare of domestic horses has been scrutinised by the scientific community in recent years. Traditional riding and stable management practices have been recognised to be at odds with the physical and behavioural adaptations of the horse. There is, therefore, a growing need to understand how modern horse management can impact on horse welfare. The first study in this thesis assessed the impact of common management practices on physiological stress in the horse. Faecal cortisol was higher in horses that were stabled and exercised, than turned out to grass with no exercise. The effect of exercise alone was also seen to increase levels of salivary cortisol. No change was seen in cortisol following short-term routine husbandry procedures such as exposure to the sound of electric coat clippers, but it was suggested that this required further investigation. The study confirmed exercise increased stress as reflected by cortisol concentration, and indicated that individual stabling may also contribute to elevated stress. The study recommended that horses may benefit from periods of rest and turn out to grass, to reduce stress levels and improve welfare. The measurement of stress for the purpose of welfare assessment is, however, best carried out using an integration of both physiological and behavioural measures. Behaviour scores offer non-invasive, quick and easy methods of assessing stress in domestic animals, but have typically been developed using only behavioural assessment of the stress response. In the second study a scale of behavioural indicators of stress was developed using behavioural and physiological measures for the purpose of assessing stress in stabled domestic horses. Principal component analysis of behavioural reactions and changes in salivary cortisol concentration in response to routine husbandry procedures, revealed three meaningful components that were used as the basis to the stress scale. Behavioural reactions to the husbandry procedures were further analysed by a panel of equestrian professionals using free choice profiling, and results were added to the appropriate components. The final scale comprised of four levels of stress (no stress, low, iii medium and high stress), and each category was further sub-divided into behaviour scores (BS). The scores represented accumulating levels of behavioural indicators of stress within each stress level, and provided indices of physiological stress. The scale offers an easy to use method of welfare assessment in horses, and reduces the need for additional physiological measures to be taken. The scale represented a novel approach to measuring stress, and was used in the final study to measure stress in horses stabled individually, group housed, and in horses moved from stabling to group housing. The effectiveness of the scale at measuring stress, was compared to the effectiveness of measures of heart rate variability (HRV) and faecal cortisol at measuring stress in the same horses. Lower levels of stress were recorded in group housed horses as measured by the BS, but measures of HRV and faecal cortisol showed no difference between those stabled or group housed. Stress levels were unaffected by the move to group housing, but BS declined significantly over the three weeks that the horses remained group housed. The physiological measures did not, however, reflect such a decrease in stress. Stress levels were also compared between horses housed in both environments whilst waiting to be fed. Group housed horses had lower stress levels as measured by the BS. Results provided by the BS were supported by relevant literature, and the scale appeared to be more sensitive than the physiological measures which did not yield significant results with the small sample sizes used in the study. The research confirmed short-term management practices horses are typically exposed to daily, can elevate their stress levels. Further research into which practices put horse welfare at a particular risk, and thus require modification or need to be avoided where possible, is necessary. The findings also suggest horse-owners may need to pay more attention to their horse’s stress levels, to avoid repeated or on-going stress that can jeopardise health and welfare. The scale of behavioural indicators of stress would provide a suitable method by which stress could be monitored and thus become a part of horse management.