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Summary
This report provides an update on the results of an exclosure study in Lake Okataina Scenic Reserve, Bay of Plenty. In 1984, three 20 x 20 m plots were established, two of which were fenced to exclude: a) dama wallaby only, and b) dama wallaby and red deer. The third plot remained unfenced. The objective was to assess the respective impacts of dama wallaby and red deer on the forest understorey.
The results show that dama wallaby mainly impacted on the seedling layer, drastically reducing seedling density and diversity, and causing the disappearance of preferred food species. Red deer did not prevent seedling establishment to the same extent, but prevented seedlings from maturing into saplings. Thus, both species had a profound effect on the composition and structure of the forest understorey, and together effected a severely depleted forest understorey.
Effective control of dama wallaby alone is likely to have some benefit for the forest ecosystem, but control of both species, wallaby and red deer, would be required to achieve full recovery of regenerative processes. Palatable species would likely return.
After five measurements over 33 years, the study now provides a good understanding of the short to medium-term effects of wallaby and red deer on the forest understorey at Lake Okataina Scenic Reserve. An understanding of long-term effects, e.g. effects on composition and structure of the forest canopy, would require ongoing monitoring. However, sufficient information may already be available in the published literature or through the Department’s National Biodiversity Monitoring and Reporting System.