Sheep-Grazing with Different Foraging Efficiences in a Dutch Mixed Grassland

Abstract

(1) In 1972, 11 ha of woodland, heathland and previously manured pasture was fenced in for a sheep-grazing experiment. The different grazing intensities in the grassland area were quantified, since it is considered a prerequisite for the establishment of heterogeneous vegetation patterns, i.e. closely grazed areas, roughness and shrub. (2) Grazing intensity, implying associated effects of treading and dunging (occupancy), can be estimated by dunging intensity. Grazing intensity implying the defoliation by animals can be estimated using exclusion cages. Despite the fact that both methods show a degree of inaccurancy they seem appropriate for nature conservation purposes. (3) Peak standing crop (including standing dead material, but excluding litter) reached 210 g m-2 in Leontodon autumnalis, 420 g m-2 in Holcus lanatus, 510 g m-2 in Agrostis capillaris, 730 g m-2 in Agrostis stolonifera, 830 g m-2 in Juncus acutiflorus, and 1130 g m-1 in Juncus effusus communities in October 1981. (4) Grazing intensity expressed as efficiency of foraging was 0.89 in Leontodon autumnalis, 0.30 in Holcus lanatus and 0-09 in Agrostis capillaris communities over a 6 month period from June to November 1981. (5) Low species diversity was related to very low efficiency of foraging, whereas species diversity was relatively high for foraging efficiencies ranging from moderate to high. (6) Grazing at an average stocking of 3 sheep ha-' resulted in a smaller area (13%) with a short turf ( 36 cm), and a much larger area (69%) with intermediate turf. (7) Measurements of foraging efficiency can enhance the ideal situation in which authorities in charge of management, knowing the herbage accumulation, could indicate preferred proportion of structural components and then determine the appropriate stocking density.