exclosures

Making use of existing fences as ready-made exclosures, this study aimed to assess the long-term effects of cattle grazing on forest margins. Results indicated: 1) that cattle browsing and trampling has an impact on vegetation species composition, structure and regeneration; 2) that the effects of a particular grazing regime may take many decades to dissipate; and 3) that the impacts of cattle change with stock intensity. Some plant species appeared to be highly palatable to cattle and only occurred on sites without cattle.

There has been considerable ongoing debate about the extent to which the impacts of introduced deer on native vegetation have replaced those of moa, and since the 1980s there have been major changes in thinking about the impacts of deer and ratites on ecosystems. Although it has long been known that deer caused a predictable sequence of changes in forest understorey composition, recent work has shown that the foliage of species preferred by deer contains lower concentrations of fibre – and decomposes faster – than avoided species.

Species abundance, species richness, and ground cover were measured over 10 years on nine paired grazed and exclosure plots in short-tussock grassland in the early stages of invasion by Hieracium species. With and without grazing, H. pilosella and H. caespitosum increased markedly and H. lepidulum increased locally. In contrast, 50% of all other common species and species groups, and total, native, and exotic species richness declined significantly.