Sixty Years of Change in a Forest Reserve: Otari Plant Museum, Wilton, Wellington

Abstract

Otari Plant Museum is a reserve of approximately fifty-six hectares on the boundaries of Wellington City. Research for this thesis was designed to complement long-term study of the reserve 1. A 1:5000 scale vegetation map of the reserve was produced. Data collected during the mapping exercise was analysed using the TWINSPAN program, confirming that the vegetation in Otari reserve consists of a podocarp/broadleaf forest remnant, bounded by Dysoxylum spectabile/Melicytus ramiflorus forest and Ulex europaeus/Myrsine australis scrub. Areas of secondary forest have increased in size, and areas which were grassed in the 1930s have developed a dense cover of scrub, containing both native and introduced species. Four permanent plots were re-surveyed, indicating that two species in the podocarp/broadleaf remnant, Beilschmiedia tawa and Elaeocarpus dentatus, are declining in numbers due to poor regeneration, and windthrow of adults. Regeneration of Dysoxylum spectabile is healthy, and the species seems likely to become the predominant canopy tree across the reserve. A comparison of permanent plots with the vegetation of two new plots indicates that the spatial patterns of canopy species are essentially random, although B.tawa shows some tendency toward aggregation. The action of natural successional processes on Otari, and the interactions of plant species are discussed, as are the effects of external agents such as wind, animals and the actions of humans, both through recreation and management. Options for future management are discussed briefly.