Biotoppflege mit Pferden

Abstract

The aim of the research project was to study the vegetation and landscape changes in a grass-dominated nature reserve, under year-round extensive grazing with free-ranging horses. The project area (107 ha) is located at the southern point of the Danish island Langeland. The herd of Exmoor Ponies (Equus ferus f. caballus) was installed in the area in October 2006. The main goal has been to support a rich plant community under the influence of large herbivores and to optimize ecological conditions for insects, amphibians and birds. Due to its robustness, the Exmoor Pony is well suited for a year-round grazing management. The stocking-rate was limited to a maximum of 0.5 livestock-units (LU) per hectare, in order to avoid additional feeding in wintertime. The sites utilization of grazing animals as well as the development of vegetation and landscape structure under the impact of grazing were examined. The horses had a great impact on the vegetation structures. The grassland consists now of lower and higher growing areas with different habitats on a low scale. Sharp boundaries between habitats have been removed. Through grazing, the ponies kept the grassland and most of the riverside vegetation open. They turned the former monotonous farmland into a botanically and ornithological diverse area. Especially in moist habitats with fluctuating water levels, the grazing impact led to the development of new plant communities. By reducing significantly the vegetation highs and quantities of biomass, seedlings of tree and shrub species were damaged by the horses. The grazing animals slowed down the outspread of bushes in the grasslands and at the forest borders. By that, they turned grasslands with initial shrub invasion back to open grasslands. However, the impact on the forested areas was low. Former pastures and meadows assimilated in their floristic diversity. Although the extension of meadows decreased slightly during the sample period, biodiversity had risen in the project area because of the upgrading of former farmland. Numbers and evenness of species have risen significantly since the grazing started, while weeds in pastureland did not increase. The study showed that it was possible to enhance the structural diversity of former intensive cultural landscape through extensive horse grazing. A rich structured biotope with free access to water resources and woods for shelter is of great importance in year-round grazing projects. The ponies displayed a spatially and temporally varying habitat use preferring nutrient-rich grassland vegetation units and low growing bankside plant communities. Drier or ruderal grassland and high growing reed beds were mostly avoided and frequented increasingly in winter time. Grazing intensities depended on distance from water as well as moisture levels and N supply of the vegetation.