Experiments on the effects of fertilizer and rabbit grazing treatments upon the vegetation of a limestone quarry floor.
Vegetation colonization in Clipsham Old Quarry, near the Leicestershire/Lincolnshire border, was studied in 1980-84. Quarrying finished about 40 years before experiments on fertilizer application and rabbit grazing were carried out. Low rates of compound (NPKMg) fertilizer was applied to some plots in 1981-82, and additional fertilizer applied to split plots in 1983-84. Grazing was manipulated by summer or all-year caging of some plots to keep rabbits out. The initial mean vegetation cover was 21.4%. This did not change over the study period in control plots (no fertilizer, unrestricted grazing), but all other treatments produced some increase. All-year protection from grazing gave an increase to 52% cover, while combinations of protection plus fertilizers gave 35-84% cover. Species richness over the whole experimental area increased from 34 to 39 species/m2, with no clear treatment effects. Species frequency within plots increased significantly in 8 of the 12 treatments, and was highest with double fertilizer application with or without protection from summer grazing by rabbits. Flowering was highest with double fertilizer application, and was also consistently increased by summer caging. Plant frequency trends are tabulated for 17 species, and 4 classes of response to treatments are described, including decreases attributed to competitive exclusion. The results are discussed in relation to natural trends, and to management practices for maintaining or enhancing diversity in species-rich quarry communities.