Long-term effects of free-ranging cattle and ponies on the soil and vegetation of reseeded grasslands in the New Forest, England

Abstract

The New Forest, England, includes an extensive area of semi-natural vegetation that is grazed by free-ranging cattle and ponies. Between 1947 and 1958, several areas of nutrient-poor acid grassland were fenced and sown with pasture seed mixtures with the aim of improving the animals’ food resources. After the swards had established, the fences were removed and the leys, known locally as reseeded lawns, have since been grazed continuously. Drawing upon data from previous studies and reports, we investigated changes in the vegetation and soils of these lawns, and in their use by grazing animals, over a period of < 75 years. The sown species, among them Lolium perenne and Trifolium repens, were soon replaced by Agrostis capillaris and rosette-forming forbs such as Hypochoeris radicata and Leontodon autumnalis. After about 1996, the cover of Danthonia decumbens and various Carex spp. increased, and heathland species, especially Calluna vulgaris, began to encroach onto the lawns. This floristic succession was associated with declining productivity and lower nutritional quality of herbage, and reduced use of lawns by livestock. We present various lines of evidence indicating that the main driver of these changes was declining soil phosphorus (P), caused in large part by its export from lawns in excreta and in the bodies of animals leaving the New Forest. We conclude that, through their selective use of habitat, free-ranging livestock can strongly influence vegetation processes at larger spatial scales and may contribute positively to the conservation value of pastoral landscapes.