Upland plant communities - sensitivity to change

The factors that influence changes in the upland plant communities of Scotl and, and hence result in changes in the landscape, are examined with partic ular reference to the decline in the cover of heather moorland. These facto rs include natural disturbances, such as climate change and fire, but the i nfluence of man-made disturbances on the landscape, notably due to sheep gr azing and deforestation. has been much greater. Despite this, it is argued that plant communities differ in their fragility and some current upland la ndscapes are not particularly sensitive to some types of disturbances, at l east under moderate herbivore loads. However, the impact of potential reduc tions in herbivore loads, in combination with other factors (e.g., climate change and increased atmospheric nitrogen deposition), on the rate of veget ation 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 th e challenge facing both ecologists and those interested in landscape manage ment. (C) 2001 Elsevier Science B.V. All rights reserved.