An experimental study of the effects of sheep grazing on vegetation change in a species-poor grassland and the role of seedling recruitment into gaps

Published source details Bullock J.M., Hill B.C., Dale M.P. & Silvertown J. (1994) An experimental study of the effects of sheep grazing on vegetation change in a species-poor grassland and the role of seedling recruitment into gaps. Journal of Applied Ecology, 31, 493-507.
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This study is summarised as evidence for the following.

	Action	Category
	Restore/create species-rich, semi-natural grassland Action Link

Restore/create species-rich, semi-natural grassland

A replicated controlled trial from 1984 to 1990 at Little Wittenham Nature Reserve, Oxfordshire, UK (Bullock et al. 1994) found that plant composition on a previously improved pasture hardly changed in response to reduced sheep grazing intensity and no fertilizer. Plant species diversity was still low after six years. The vegetation remained dominated by perennial grasses, with four species making up 80% of records. Herbaceous plants (non-grasses) made up just 0.4% of records. Seventy percent of seedlings growing in artificial gaps in the grass cover were of two grass species, perennial rye grass Lolium perenne and meadow barley Hordeum secalinum. Only 4% of seedlings were non-grass species, and none were species not already found in the paddocks. There was no evidence of a seed bank (gaps with original topsoil did not differ from gaps with topsoil replaced by sterile soil). There were eight levels of sheep grazing: summer grazing to a height of either 3 cm (more intensive) or 9 cm (less intensive), with or without winter and/or spring grazing, but grazing intensity had only small effects on the vegetation. Each treatment was replicated in two 50 x 50 m paddocks. Plants were surveyed using a point quadrat at 64 points/paddock in 1990. Vegetation and topsoil or vegetation-only were removed in September 1990 in five 10 cm diameter circles/paddock and seedlings growing in these areas counted and removed regularly until January 1992.