Published online by Cambridge University Press: 24 August 2009
Plant communities produced experimentally in twometres' square plots on the rubble-covered floor of a limestone quarry showed changes in the cover values that were attributable to the sown grass and to immigrant mosses over a period of three years. Cover values for the mosses were lower in summer than in the following autumn over two cycles, whilst the cover that was attributable to the sown grass, a non-rhizomatous cultivar of Festuca rubra, did not follow a clear pattern. No evidence of directional change was found; this suggests a stable coexistence of the grass with mosses. It is suggested that one property of such a community will be a differentiation of regeneration niches which are favourable to an increase of diversity through immigration.
Episodic persistent flooding and consequent deposition of colloidal limestone on well-established and diversifying vegetation, followed by a single catastrophic incident of compression by the tyres of heavy vehicles, resulted in the loss of F. rubra and mosses, and the ascendency of a perennial survivor (Agrostis stolonifera).