Regeneration of Pinus sylvestris in a natural pinewood in NE Scotland following reduction in grazing by Cervus elaphus

The occurrence of Scots pine (Pinus sylvestris L.) seedlings and saplings ( <2.0 m in height and suppressed by grazing) and ground characteristics were recorded in a 300 ha block of natural pine forest in 1993. The density of red deer (Cervus elaphus L.) was then reduced by exclosure to approximately 3-4 deer km(-2), which is below the threshold at which pine regeneration s hould occur. Numbers and performance of pine seedlings and saplings were fu rther monitored 2 and 4 years after exclosure. Numbers of young pine increa sed over time. In the three years with observations 97-99% of pine seedling s and saplings were recorded within 20 m of a seed source. Stepwise multipl e regression was used to explore the relationships of pine establishment wi th plot characteristics for (a) all observation plots (n = 178) and (b) plo ts within 20 m of a seed source (n = 154). The factors most closely related to the number of pine seedlings and saplings in 1997 were, for (a), seed-s ource distance, vegetation height, blaebeny cover, slope and deer pellet-gr oup density in 1993, all but the last having negative effects. For (b), veg etation height, blaebeny cover and slope were again selected predictors, an d again had negative effects. Possible mechanisms by which the selected mai n effects may influence pine regeneration are discussed, the positive relat ionship to deer density being considered to reflect the creation of gaps in the sward suitable for germination. However, the amounts of variation expl ained in the models were low, being 16% for (a) and 13% for (b), reflecting the patchy nature and diverse age of the regeneration. (C) 2000 Elsevier S cience B.V. All rights reserved.