Effects of Ungulates on Structure and Species Composition in the Urewera Forests as Shown by Exclosures

Seventeen exclosures were built by the New Zealand Forest Service within Urewera forests over the period 1961-68 to exclude ungulates. Forest structure and species composition inside and outside these exclosures were compared in 1980-81. Some relatively shade tolerant species such as the fern Asplenium bulbiferum, the liane Ripogonum scandens, the sub-canopy shrubs Geniostoma ligustrifolium and Coprosma australis and the canopy species Beilschmiedia tawa were less abundant in certain tiers outside the exclosures than inside. By contrast, only a few species were more abundant outside then inside the exclosures. These included the unpalatable shrub Pseudowintera colorata, turf-forming Uncinia species and Cardamine debilis. Overall density and species richness for small diametered trees and for the sapling tier were lower outside the exclosures than inside. Despite the large reduction in ungulate numbers throughout Urewera forests these introduced browsing animals, particularly deer, still affect the structure and composition of most forest types.