Changes in Two High Altitude Blanket Bogs after the Cessation of Sheep Grazing

Abstract

(1) A 15-year botanical study on the effects of excluding sheep from 350-m2 fenced areas on two high-altitude Eriophoretum blanket bogs has been carried out on Moor House National Nature Reserve. (2) The poverty of the bogs is stressed; they were species-poor, of little cover, and erosion was active. (3) Climate had previously been considered the main factor controlling the vegetation, but the importance of sheep grazing soon became apparent. After 14-year protection both bogs had undergone major changes in species composition, pattern of vegetation and structure. (4) Calluna vulgaris, from an early position of scarcity, grew to dominate parts of each exclosure, whilst the cover of Empetrum nigrum trebled in the same period. However, Empetrum nigrum, after having dominated more than 10% of each bog in the mid-term of the study, finally gave way to Calluna vulgaris. (5) Rubus chamaemorus and Narthecium ossifragum (the latter present only in one exclosure) increased spectacularly, but Trichophorum cespitosum became intermingled in the developing vegetation and lost its distinctive homogeneous community pattern. (6) Leafy liverworts, in particular Diplophyllum albicans, a constant of the high-level Eriophoretum facies, declined; the colonization of bare peat was slow. (7) Botanical composition, structure and density altered in the direction of Calluneto-Eriophoretum, a move recommended as an improvement for wildlife and possibly agriculture. To test the agricultural benefit would require further experiments.