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Experiments on the Effects of Fertilizer and Rabbit Grazing Treatments Upon the Vegetation of a Limestone Quarry Floor
B. N. K. Davis, K. H. Lakhani and M. C. Brown
Journal of Applied Ecology
Vol. 30, No. 4 (1993), pp. 615-628
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2404241
Page Count: 14
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1. A study is described in which two very low levels of fertilizer application and three levels of rabbit grazing treatments were used to accelerate the colonization of a limestone quarry floor from an initial mean vegetation cover of 21.4%. A factorial experiment was laid out with six randomized blocks, each with six plots. An `extra-fertilizer' treatment was added later by splitting the plots. 2. All treatment combinations were studied over 5 years for their effects upon the percentage cover of vegetation, species richness, species frequency and the number of species in flower. 3. There was virtually no change in mean percentage cover values in the control plots (no fertilizer, unrestricted grazing), but all the other treatments produced some increase. This was especially evident with all-year protection from grazing (increase to 52%), and with combinations of protection plus fertilizers (increases to 35-84%). 4. There was a gradual increase in species richness over the whole experimental area during this period from 34 species m-2 to 39 m-2, but the effects of particular treatment combinations were less distinct. Species frequency within plots increased significantly under 8 of the 12 treatments. Highest values resulted from double fertilizer applications with or without protection from summer grazing by rabbits. The double fertilizer combination gave the greatest number of species in flower. 5. Trends for individual species were examined and four classes of response to treatments are described, including declines attributed to competitive exclusion. 6. These results are discussed in relation to natural trends, and to management practices for maintaining or enhancing diversity in such species-rich quarry communities.
Journal of Applied Ecology © 1993 British Ecological Society