An Ecological Investigation at a Junction Between Two Plant Communities in Coombsdale on the Derbyshire Limestone

Abstract

In Coombsdale, Derbyshire, a rendzina has been rapidly converted into a shallow acid humus soil (limestone ranker) dominated by the calcifuge Deschampsia flexuosa. Stages in the transformation are: (1) surface leaching of the rendzina; (2) invasion by seedlings of D. flexuosa; (2) elimination of many established calcicoles, notably Festuca ovina, by "interference" from Deschampsia flexuosa; (4) accumulation of more humus;.(5) failure of seedling regeneration in calcicolous species. On the rendzina, the slow growth rate of calcicoles and calcifuges is primarily an effect of nutrient deficiencies but fatalities occur during drought. Surface leaching is associated with an increase in available P and is followed by an increase in the density of both calcicoles and calcifuges, resulting in closure of the turf. Desiccation is less effective on the ranker because of the higher moisture-holding capacity. Limestone ranker soils revert to rendzinas on burning and probably also following severe drought and erosion. It seems likely that, in many situations in Derbyshire, limestone rankers will occur as transient phenomena initiated by a succession of abnormally moist summers.