Recovery of a dwarf birch (Betula nana) population following reduction in grazing by red deer (Cervus elaphus)

Summary

In Britain Betula nana is a nationally scarce plant, its distribution being limited by climate, heather burning and grazing by deer and sheep. The recovery of a population of B. nana was monitored for several years inside a Scots pine regeneration exclosure in N.E. Scotland. Browsing pressure was reduced in the exclosure but a few red deer (amounting to 3–4 km^?2) were deliberately retained. B. nana stem density increased after red-deer density was reduced. Over the same period there was a reduction in browsing inside the exclosure. B. nana stem density was negatively related to heather height, deer presence and tree canopy cover. Comparisons of growth were made with plants outside the exclosure between 1998 and 2000, the mean annual increment of stems, allowing for browsing loss, being respectively 1.25 and 0.45 cm for inside and outside the exclosure. Most stem basal diameters inside the exclosure were smaller than outside. Reducing red deer density to 3–4 km^?2 on similar upland sites with peaty soils could lead to regeneration of B. nana.