The University of Arizona

Seasonal diets of sheep in the steppe region of Tierra del Fuego, Argentina.

G. Posse, J. Anchorena, M.B. Collantes

Abstract


Sheep diets were determined seasonally for large flocks grazing year-round in 2 landscape types of the Magellanic steppe of Argentina. A tussock-grass steppe of Festuca gracillima Hooker f. dominates the uplands of the whole area. On acid soils (Quaternary landscape), woody variants of the steppe prevail; on neutral soils (Tertiary landscape), woody plants are almost absent and short grasses and fortes are abundant. Principal taxa consumed throughout the year were: Poa L., Deschampsia P.Beauv., and "sedges &rushes". Consumption of woody species and of the dominant tussock-grass Festuca gracillima increased notably in winter. Despite the large proportion of species in common, diets differed significantly between landscapes. In the Quaternary landscape, which has a higher botanical diversity, diets were more dissimilar among seasons and had a higher annual diversity index. Because of their different composition of forage types the 2 landscapes differed in their overall grazing value. The Tertiary landscape, with a low floristic diversity but richer in highly preferred species as Poa spp. would be a more risky grazing area in winter, when an ice sheet or a snow cover limits harvesting of the lower layer of short grasses and forbs.

Keywords


tertiary sediments;festuca gracillima;Festuca;tussock grasslands;steppes;steppe soils;species diversity;diet;woody plants;sheep;seasonal variation;Argentina;canopy;forage

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