Herbivory and plant ecology

The dominance of large herbivore grazing as a factor which limits the extent of the UK montane willow communities is demonstrated by vigorous growth of willow inside large mammal exclosures (e.g. Pollock, 2000). Whilst this suggests a top-down control of the willow community by vertebrate herbivores, much evidence suggests that the associated invertebrate communities are limited by the bottom-up influence of food quantity or quality provided by the willows (e.g. Roininen et al., 1996).

We tested the overall hypothesis that exclusion of large herbivores will lead to several possible ecological interactions of relevance to the gene flow, persistence, development and conservation of the communities. To address this, field experiments were conducted to examine the effect of grazing intensity on insect herbivory, the effect of large herbivore exclusion on pollination biology and seed production and the factors affecting seed and seedling mortality.