Total protein and macroelement content in selected psammophilous grassland species under free-range sheep grazing in Kozki Nature Reserve

Psammophilous grasslands are among the most valuable but also severely threatened habitats protected within the Natura 2000 network and, like most grassy ecosystems, they are also subject to secondary succession. Grazing has turned out to be an adequate conservation measure in inland sand ecosystems. Sheep are small ruminants which ingest plant species ignored by other livestock species; they also eat some undesirable plants containing toxic alkaloids and glycosides. The study objective is to assess the macroelement content of plants ingested by sheep of the breed called Świniarka. Regarded as being of low value, these plants occur in the sward of psammophilous grasslands in Kózki Nature Reserve. The Braun-Blanquet method was used to study the vegetation cover and identify the type of a plant community. The total protein, phosphorus, potassium, magnesium and sulphur content in the aerial biomass of selected plant species (Armeria maritima, Calamagrostis epigejos, Carex praecox, Corynephorus canescens, Cynoglossum officinale, Dianthus deltoides, Juniperus communis, Koeleria glauca, Sedum acre and Thymus pulegioides) was determined. The analysed plant species occurred in the floristically rich psammophilous grasslands of the Vicio lathyroidis-Potentillion argenteae alliance, Spergulo-Corynephoretum association and in a community with the predominance of Calamagrostis epigejos. The biomass of psammophilous grasslands was characterised by a very low content of protein and phosphorus, potassium, magnesium and sulphur, in most cases below the optimum levels that would satisfy the nutritional requirements of animals. The biomass of Cynoglossum officinale had the significantly highest content of protein, phosphorus and magnesium, which could have been the reason why this species, despite its poisonous properties, was ingested by the Świniarka sheep grazing under the poor conditions of psammophilous grasslands. Species typical of psammophilous grasslands, such as Corynephorus canescens or Koeleria glauca, had the lowest nutritional value. C. canescens and Sedum acre were not ingested by sheep.