Topic C
The effects of horse grazing on species diversity in permanent pasture on an organic farm in Worcestershire
Grasslands are affected by their management, including the effects of grazing animals (e.g. Putman, 1986).
In this investigation the seasonality of plant growth meant that the time of data collection could affect the species recorded. Reading indicated that most grassland species would be visible above ground during the summer. It was also clear that grassland surveys usually use 2m x 2m quadrats. The student decided to use two measures. The first was species diversity (i.e. the total number of species found in each quadrat). The second measure she used was species abundance indicated by Domin scores.
The two adjacent permanent pastures used in this study had been established for at least 15 years and grazed exclusively by horses for the past 10 years. The stocking rate had varied during that time but the pattern of management had been the same throughout. The two pastures had not been artificially fertilised. In both pastures during late autumn-early spring the horses were allowed to graze the whole field. On the 'grazed field' during the summer the grazing was restricted on a rotational basis and the horse manure removed by hand. The 'rested' field was not grazed during the summer but the grass was lightly mown in late autumn.
References
PUTMAN, R.J. (1986). Grazing in temperate ecosystems - Large herbivores and the ecology of the New Forest. Croom Helm Ltd, London.
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