Floristic changes in grazed-down heather moorland

What is it about?

Vegetation and herbivore usage at three moorland sites were monitored for 43-44 years. Heavy grazing soon caused Calluna to be replaced by graminoid species, and this paper is concerned mostly with the floristics of the new grasslands observed over the last 20-23 years of the study. Compositional changes in this period were minor, with no change in the best-fit allegiances to NVC vegetation types. At one site where the livestock were restricted to a relatively small range within which some reseeding occurred, the vegetation belonged to NVC Lolium-Cynosurus grassland MG6b despite not having been ploughed. At a second site the vegetation was NVC Agrostis-Festuca-Galium grassland U4d with much Luzula multiflora. At the third site the vegetation was NVC U4a but fairly rich in species including some of NVC Festuca-Agrostis-Thymus grassland CG10. This last site has conservation value due both to the rarity of the grassland type in NE Scotland and the occurrence of rare angiosperms. The driver of change at the three sites was thought to be the grazing exerted, and no evidence was found of species composition reacting to climate change or nitrogen deposition.

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Why is it important?

Heather moorland in Britain frequently suffers heavy grazing, with possible consequences for bio-diversity