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Sheep on heather-grass mosaic The subject


Spatial pattern and process in the fragmentation of heather moorland.

Problem definition

Current decisions on management of heather moorland are based on the ‘40%’ rules of thumb. The rule states that heather moorland will not be significantly damaged as long as the average heather utilisation does not exceed 40%. This rule does not consider the spatial distribution of vegetation and utilisation. Even under an average heather utilisation of 40%, the heather utilisation will locally exceed this percentage. High grazing pressure on heather moorland can lead to fragmentation of the heather and invasion of grasses. The lack of understanding of the interaction between plants and herbivores can prevent sustainable management of heather moorland.


  1. To understand the processes behind the spatial distribution of heather utilisation across a heather moorland.
  2. To understand processes behind initialisation and expansion of fragmentation of a heather matrix.
  3. To understand the roles of sheep, deer and rabbits in heather fragmentation.
  4. To supply an alternative to the 40% rule of thumb, which takes into account the spatial distribution of heather utilisation.


  1. Quantify the interaction between vegetation pattern and herbivore utilisation distribution under different sheep densities.
  2. Study the interaction between herbivores and heather/grass mosaics through a simulation model.
  3. Study the interaction between different herbivores and the influence of the interaction on performance and vegetation pattern.
  4. Evaluate hypothesis through the study of the dynamic behaviour of the simulation model based on different theoretical and empirical assumptions (virtual experiments). Experiments carried out with HOOFS.


Dr. A.J. Hester, Plant Ecology & Community Dynamics Program, Macaulay Land Use Research Institute
Dr. C.J. Legg, Institute of Ecology and Resource Management University of Edinburgh


Dr. J.A. Beecham, Animal Ecology in Grazed Ecosystems Program, Macaulay Land Use Research Institute
Dr. D.R. Miller, Land Use Change Program, Macaulay Land Use Research Institute
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