Individual study: The effect of summer sheep grazing vs. annual autumn mowing on vegetation composition and structure of four chalk grasslands in the Netherlands
Mitchley J. & Willems J.H. (1995) Vertical canopy structure of Dutch chalk grasslands in relation to their management. Vegetatio (now Plant Ecology). Plant Ecology, 17-27
Late summer/autumn mowing (and removal of cuttings) and sheep-grazing are often used in the management of calcareous grasslands in Western Europe. In this present study, the effect of summer sheep grazing vs. annual autumn mowing on vegetation composition and structure of four chalk grasslands in the Netherlands was assessed through analysis of leaf canopy overtopping relationships (using a non-destructive point quadrat method) followed by harvest of the above-ground plant material; the paper primarily compares the efficacy of these two methods of vegetation analysis, but also gives insight into the influence on vegetation structure and composition that the two management regimes have on chalk grassland vegetation.
Study sites: Four chalk (Mesobromion dry brome) grasslands characterised by tor-grass Brachypodium pinnatum were selected and surveyed in August 1985:
Wrakelberg Nature Reserve (50°52'N; 5º55'E) - since the early 1960's the grassland was managed by annual mowing and removal of cut material, usually in late October; no fertilizers had been applied during this period.
Kunderberg Nature Reserve (50º52'N; 5°56'E) - ancient grassland; between 1961 and 1980 the site was managed by annual mowing, between 1980-1983 most of the slope was managed by late autumn burning, then subsequently annual mowing was re-introduced
Gerendal Nature Reserve (50°50’ N; 5°50'E) ‘mown site’ - upto 1967 a heavily fertilized (false oat-grass Arrhenatherum elatius-dominated) hay meadow, since when (after Nature Reserve designation) fertilizer application ceased with succession towards a Mesobromion community. Since 1970 it has been managed by mowing in late October.
Gerendal Nature Reserve ‘grazed site’ - a 0.75 ha area to the south of the mown site; since 1973, managed by summer sheep grazing resulting in short vegetation of patchy appearance.
Sampling: At the three ungrazed sites in August, photosynthetically active radiation (PAR) was measured. Analysis of leaf canopy overtopping relationships was carried out using a point quadrat method, followed by stratified harvest of above-ground plant biomass.
In the annually mown grasslands, tall B. pinnatum growth was evident, this reduced PAR in the lower canopy and suppressed most smaller plants except those able to reach the higher canopy levels, e.g. wild marjoram Origanum vulgare. In contrast, summer sheep-grazing (grazing intensity or grazing dates not given in original paper) resulted in a reduction of dominance of tall graminoids (such as B. pinnatum) and taller, grazing-sensitive herbs, e.g. O.vulgare and meadow vetchling Lathyrus pratensis, and an increase in grazing-tolerant species, e.g. smaller rosette-forming herbs, e.g. rough hawkbit Leontodon hispidus and shorter graminoids, e.g. glaucous sedge Carex flacca and quaking grass Briza media.
In terms of management for conservation of calcareous grassland plants therefore, summer sheep-grazing was generally more preferable to autumn mowing.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.springerlink.com/content/p124540773868623/fulltext.pdf