The floristic changes of Scottish moorland dominated by heather (Calluna vulgaris, Ericaceae) but unburnt for 50 years and kept checked by moderate grazing

Vegetation and herbivore usage have been monitored since 1969/1970 at four moorland sites where heather (Calluna vulgaris) remained the main species under moderate levels of grazing. Much of the annual growth of the heather was regularly consumed by this grazing, but no burning occurred to remove heather biomass. Two sites were on acidic base-poor soils and had only minor cover of grasses and herbs, their vegetation having most affinity to H10 heath in the National Vegetation Classification of British plant communities. The other two sites were on more base-rich soils, and grasses and herbs had substantial cover; their vegetation showed most affinity to NVC CG11a grassland. One of the latter sites lies at 700 m and Calluna grew poorly being close to its altitudinal limit; the other three sites were at lower altitude and Calluna grew strongly creating dense swards. Over the 43–44 years of observation Calluna increased moderately in height but many subordinate higher plants declined in cover, as measured by point-quadrat recording. Bryophytes increased at three sites largely due to substantial gains of Hylocomium splendens, but other pleurocarpous mosses suffered some declines. At the three lower-altitude sites species number fell by 20–35% between the first and last recordings, but at the high-altitude site there was negligible change in species number. The main drivers of change were the grazing received and the performance of Calluna, and no evidence was found of species composition reacting to climate change or nitrogen deposition. To maintain diversity, timely burning is recommended.