Individual study: Implications of red deer Cervus elaphus grazing to ground vegetation and invertebrate communities in native pinewoods in the Highlands of Scotland
Baines D., Sage R.B. & Baines M.M. (1994) The implications of red deer grazing to ground vegetation and invertebrate communities of Scottish native pinewoods. Journal of Applied Ecology, 31, 776-783
Young of forest grouse species, particularly capercaille Tetrao urogallus in Scotland, are associated with bilberry Vaccinium myrtillus, consuming their leaves and shoots, and lepidopterous larvae. The effect of grazing of ground vegetation by red deer Cervus elaphus was assessed in eight native pinewoods in the Scottish Highlands.
Study sites: Eight native pinewoods across the Scottish Highlands: Glen Tanar, Ballochbuie, Abernethy, Glen Feshie, The Black Wood of Rannoch, Meggernie, Black Mount and Tyndrum were selected. These formed a rough east-west transect. Ground vegetation was dominated by a mosaic of heather Calluna vulgaris, bilberry and cowberry Vaccinium vitis-ideae.
The effect of deer grazing: The effect of grazing of ground vegetation by red deer was assessed in the eight pinewoods in 1991 and 1992 by comparing vegetation and invertebrate communities in grazed forest with adjacent ungrazed deer exclosures.
Grazing by red deer was associated with 44 % less heather cover and over twice as much grass. Bilberry cover remained the same, but grazed bilberry was half the height and less than half the biomass of ungrazed bilberry in exclosures, and had almost twice as many of its apical tips and buds removed.
On average, numbers of lepidopteran larvae in grazing exclosures were almost 4-fold higher, Hymenoptera, chiefly ants Formica rufa 3-fold higher, and Coleoptera, Aranaea, Diptera and Plecoptera all 2-fold higher than in grazed forest.
Conclusions: Deer grazing reduced the quality of bilberry, and lepitopteran larvae were almost 4-times more numerous in the deer exclosures. Reductions in larval abundance may have knock on effects upon those animals dependant upon them for food. For example peak larval abundance occurs in June, coinciding with the hatching period of many insectivorous birds. Local and declining species such as capercaillie have poor chick survival and this has been linked to reduced insect abundance in recent decades.
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://links.jstor.org/sici?sici=0021-8901%28199411%2931%3A4%3C776%3ATIORDG%3E2.0.CO%3B2-A