Tuesday, April 14, 2015

A Great Year for Flowering Rata Vines on the 5 Mile Track, Okarito

The forests of South Westland are unique to the area due to the effects of glaciation 12-20 thousand years ago. Throughout the rest of the South Island, forests are predominantly beech trees. On the West Coast there is a distinctive “beech gap”, where beech trees have failed to re-colonise after the forest was removed during the ice age, and  glaciers covered all the land down to the sea-shore. After the glaciers receded this land was recolonised by tree species that had their seeds spread by birds or wind, unlike the beech which seeds are spread by gravity or water.
One of the more noticeable tree species occupying the “beech gap” is the southern rata, related to the northern pohutakawa, and the iron woods of the pacific region. Rata trees cover the mountain sides around Franz Josef and display a profusion of red flowers in January and February. Bee keepers exploit this profusion of nectar bearing flowers by positioning bee hives near the rata forests. Stacked bee hive boxes lie alongside the road like mini condominiums. Rata honey has a distinctive earthy smell.
Unfortunately rata trees are a highly desired food source for the introduced pest, the Australian brush tailed possum. A cat sized marsupial, possums were introduced into New Zealand to establish a fur trade, and have become a major environmental pest. You may see these animals as road kill, distinctive with the curled black tail and red or grey fur. Possums strip the flowers and leaves of the large rata trees and eventually kill them by long term defoliation, leading to the collapse of the forest canopy and its replacement with less palatable shrubs.
In an effort to protect the rata forests and their associated ecosystem, the Department of Conservation (DOC) conducts periodic possum culling operations, using poison baits dropped over the forests by helicopter. 

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