Upland plant communities — sensitivity to change

The factors that influence changes in the upland plant communities of Scotland, and hence result in changes in the landscape, are examined with particular reference to the decline in the cover of heather moorland. These factors include natural disturbances, such as climate change and fire, but the influence of man-made disturbances on the landscape, notably due to sheep grazing and deforestation, has been much greater. Despite this, it is argued that plant communities differ in their fragility and some current upland landscapes are not particularly sensitive to some types of disturbances, at least under moderate herbivore loads. However, the impact of potential reductions in herbivore loads, in combination with other factors (e.g., climate change and increased atmospheric nitrogen deposition), on the rate of vegetation change cannot be predicted with confidence at present. Understanding the mechanisms underlying spatial and temporal variation in the sensitivity of upland plant communities to increasing disturbances in the future is the challenge facing both ecologists and those interested in landscape management.