Post-management vegetation change in upland heather moorland, with particular reference to the nutrient status of soils
: Lake Vyrnwy Estate, Powys, Mid Wales

  • Ronald Johnston

    Student thesis: Doctoral Thesis


    A major component of the vegetation cover in the area chosen for this study consists of heather moorland. This provides an essential habitat for diverse populations of ground-nesting moorland birds. Common heather - Calluna vulgaris (L) Hull - is typically the dominant species of this semi-natural habitat, providing both nutrition and cover for these bird populations.

    Much heather-dominated vegetation is in a successional stage and management is required to prevent its progressive transformation into rough grassland and woodland scrub. Traditionally management by burning and more recently by mowing has been used to achieve this by encouraging the growth of young heather, through the removal of senescent stands of Calluna vulgaris in the degenerate phase of its life cycle. These forms of management however may also have the effect of creating conditions which favour faster growing, acidophilous grasses which may replace Calluna vulgaris over time as the dominant species.

    This study investigates the hypothesis that particular management treatments may have specific influences on the composition and nature of the post-management vegetation complex. Particular attention is given to the nutrient status of soils, associated with each of the management treatments chosen for investigation. The influence of this on the long-term floristic composition and vertical stratification of the Callunetum is considered.

    Stands of vegetation belonging to different management regimes were used as the elements of chronosequences, which were utilised to investigate vegetation change over time in relation to particular management treatments. Vegetation was described from quadrats located within this framework and quadrat-specific soil samples were taken for chemical analysis.

    Dendrochronology was explored as a method for determining the age of Calluna plants in each treatment category from which the efficiency of different methods of removing the Calluna canopy was assessed. Multivariate methods of classification (TWINSPAN) and indirect gradient analysis (DECORANA) were used to reveal pattern in the vegetation data, which might be attributable to the management treatments defining each of the chronosequence stages.

    TWINSPAN was successful in identifying homogenous groups of samples on the basis of species associations peculiar to particular treatment categories. DECORANA proved successful in suggesting environmental gradients which might be responsible for these groupings.

    Data obtained from the chemical analysis of soil samples was used to compare soil nutrient status in each of the treatment categories, representative of the chronosequence stages. The vegetation and soils data-sets were then combined for use in direct gradient analysis (CANOCO), to investigate the combination of management treatments and soil nutrient status as factors influencing the formation of the species associations identified at each of the chronosequence stages.

    Finally, management goals are discussed in the context of the results of these analyses and the role of these procedures as the basis for an extended investigation into post-management, plant / soil inter-relationships as an influence on successional trends is evaluated.

    Date of Award1998
    Original languageEnglish


    • Plant ecology
    • soils
    • vegetation
    • environmental management

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