Year-round horse grazing supports typical vascular plant species, orchids and rare bird communities in a dry calcareous grassland

Abstract

Large herbivores, such as robust horse breeds, are increasingly used to develop and maintain open habitats. However, their use on calcareous grasslands has rarely been tested. On the one hand, conservationists fear an unequal use of the pasture with partial abandonment, encroachment or reduced ground light conditions, as well as partial over-grazing with negative effects as soil erosion, latrines, grazing lawns, disturbance to the ground or shrub nesting bird species due to enhanced trampling, or impairing of typical plant species. On the other hand, it is well known that large herbivore grazing is an economical alternative where traditional sheep grazing is no longer profitable. From 2010–2014, we studied horse activity (Koniks), habitat parameters (percent dung, shrub, short vegetation, and bare ground cover), and frequency of orchids and birds using a raster approach within a 90ha year-round pasture. Vegetation composition and structure was sampled on 25m2 plots from 2009 to 2014.All habitat parameters indicated a relatively equal horse utilization of the whole pasture and neither latrines nor partial abandonment were observed. After five years, shrub encroachment on the whole pasture was restricted from 13.7 (±17.0) to 12.0% (±15.3). Vegetation litter was reduced by 60% and the mean number of species typical for dry calcareous grasslands increased by one third on the 25m2 plots. The studied orchid species as well as the target bird species were not impaired by the grazers and plots not occupied by these species showed an equal or even lower grazing frequency. The positive grazing effects such as enhanced site conditions seem to outweigh the potentially negative effects through trampling or grazing. We conclude that in large-scale calcareous grasslands low-intensity year-round grazing with large herbivores is suitable for maintaining and even improving species diversity.