A commentary on canopy tree mortality in Westland rata-kamahi protection forests.

Authors: G. H. Stewart, T. T. Veblen
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1982, Issue N.Z.J.For. 27(2) 1982, pp 168-188, Aug 1982
Publisher: New Zealand Institute of Forestry

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Abstract: The apparently excessive canopy tree mortality in the rata-kamahi forests of Westland has resulted in the widespread belief that persistence of the forest cover in this area may be endangered. Browsing by the Australian brush-tailed possum (Trichosurus vulpecula) is commonly believed to be the cause of the widespread mortality. Consequently', research has been directed towards studies of possum diet and vegetation condition under varying possum densities. However, browsing by possums does not appear to be the sole cause of the tree mortality. Natural stand dynamic processes appear to contribute importantly to the observed mortality patterns. The development of even-aged stands following massive disturbances such as mass movements and windthrow and, thus, the presence of groups of senescent trees appears to be an important contributory factor. Possum browsing (as well as other lethal influences) may be affecting stands already susceptible as a result of natural stand dynamic processes.

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