This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The similarity between the true heath and the grass heath suggests that a heath may ultimately pass into pasture. Heaths may, in fact, at their margin, grade into dry pastures without Ling or other heath plants. This is merely the illustration of a natural law of succession. The transition of heath into pasture in this manner, however, must not be confused with the existence of vestiges of true heath or grass heath amongst neutral grassland, for in this case cultivation has been the determining factor. It is true that the result is largely the same, but the originating cause (and process) is dissimilar. This fact may be illustrated by the study of a heath locally and its marginal transition to pasture or grass heath, and the comparison between this type and the possible representa-tion of a vestigial heath in the same area.
In the transition from heath to pasture it is interesting to note the elimination of the Ericaceous dry-soil types, and the persistence or appearance of ordinary meadow types. Once the Ling and Heath, or Furze, or Oak, or Pine are removed, a new flora comes into existence. The transition from grass heath which thus results is very easy, into a normal, dry pasture. Indeed, many dry pastures may be found to retain a few traces of their former condition, including some dry-soil types, as Mountain Everlasting, etc. By drainage, the wet-heath types also disappear, and there may then be little left to indicate the former character of the vegetation.