Effects of Added Nutrients on Dune Swards Grazed by Rabbits

Abstract

(1) Different combinations of nitrogen, phosphorus and potassium were added to two nutrient-poor, rabbit-grazed dune swards at Holkham, Norfolk. The plant communities included a wide range of annual species with some perennial species, bryophytes and lichens. The complete (+NPK) mixture was also applied at higher concentrations to establish the effect of differing rates of application. (2) Because of intense rabbit grazing in the area, perennial grasses did not dominate the sward, and only very few unpalatable perennials were favoured by nutrient addition. (3) Annual species generally declined in frequency when fertilizer was added, as did the cover of bryophytes and lichens, with a reduction in species diversity. This was most marked with treatments containing nitrogen. The reaction to phosphate and potassium treatments differed according to species. (4) The relatively diverse plant communities at Holkham apparently owe their existence both to low nutrient status and to relatively high rabbit grazing intensity. The importance of differential response to nutrients by species, and of local variation in soil nutrient supply is considered in relation to niche separation.