The implications of red deer grazing to ground vegetation and invertebrate communities of Scottish native pinewoods.
Abstract
The effect of grazing by red deer (Cervus elaphus) was assessed in eight native pinewoods (dominated by Pinus sylvestris) in the Scottish Highlands in 1991 and 1992 by comparing ground vegetation and invertebrate communities in grazed forest with adjacent ungrazed deer exclosures. Grazing was associated with less Calluna vulgaris and more grass. Vaccinium myrtillus cover remained the same, but grazed V. myrtillus was half the height of ungrazed V. myrtillus and had almost twice as many of its apical tips removed. Lepidopterous larvae formed 60% of all invertebrates. Four species comprised 96% of larvae, with those of Hydriomena furcata most numerous (39%). Forests in the west (Argyll) had, on average, more than 7-fold fewer lepidopterous larvae than those in the east (Deeside). Rates of decrease towards the west differed between species. On average, numbers of lepidopterous larvae in grazing exclosures were almost 4-fold higher, Hymenoptera, chiefly ants (Formica rufa) 3-fold higher, and Coleoptera, Araneae, Diptera and Plecoptera all 2-fold higher than in grazed forest. The importance of deer grazing and tree density in determining larval abundance and their subsequent potential for affecting insectivorous birds in pinewoods are discussed.