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The Otago UniversityScience Students'Association1989 Field Report:

Haast.A multidisciplinary study.

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lake. Large leaved Griselinia al;rd Arktotelia wene present along the road or as epiphyes.Supplejack was absent. On the poorest soils on the high spots above the lake, the forest wasreduced to low-canopy dominated by rimu, bog pine, pink pine and celery pine.

A day was spent in the kahikatea forest between branches of the Waita River. Kahikatea isdominant although matai, miro, rimu, P/ly llocla&s, totara (possibly including Hall's,acutifolia, and waihohensis) are present. Griselinia is present as epiphytes. Supplejack andtree ferns ar common, although the forest floor, in strong contrast to the forest north of theHaast River, is dry, open, and easy to walk through. Its open nature is probably at leastpartially due to periodic river flood events, although cattle are present in the area. The forestfloor is covered with a network of drainage channels, often just a few centimetres deep. Thissystem acts mostly to flush the litter from the forest floor, but was noted to have thick litterdeposits (tens of centimetes) locally.

TaphonomyIn the forest situations, leaves from all taxa present are well represented in the forest floorlitter (the very small leaves from divaricate shnrbs were not searched for). The tree fem(Dicksonia squarrosa) and the podocarps; Hall's totara, kahikatea, rimu, miro and matai, allproduce aQundant litter which would be expected to prcserve well. Paniculate inflorescences ofkarnaln (weiwrunia racemosa) were observed both on surrounding trees and on and within thefloor litter (a kamahi inllorescence has been recorded from the Manuherikia Group althoughleaves have not yet been identifred). However, in all the areas where plant material wasaccumulating - in the mires and in pools within the swamp forest, well preserved plant materialis present only on the surface centimetre or two. Beside this, leaves and shoots have decayedand only harder rnaterial, such as wood, is preserved- It is clear that in these 'in situ' litteraccumulations, a dramatic influx of sediment would be necessary to remove litter from the zoneof soil development and provide for their long+errn preservation.

Vegetation History

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My work on the Early Miocene Manuherikia Group, in addition to that of other workers, rhas lead me to believe that the present flora of New Zealand, from an assemblage point of view, Iis of recent, probably Pleistocene age, and is an impoverished relict of the Tertiary flora. Thelack of dramatic change between present floras growing on granite or alluvial soils, or even Ibetween those generally impoverished soils on the west coast, and the rich basaltic soils Faround Dunedin, suggest that, with a few exceptions recent taxa could be accorded'weed Istatus. They are survivors of the ice-ages, or perhaps non-specialised products of recent Ievolution. They are opportunists and pioneer qpes which can 'stick it out'in refugia andquickly colonise a variety of sites when the situation improves. I

IIReferencePole, M.S. (1989) Macropaleobotany of the Miocene Manuherikia Group of NewZealand. PhD thesis, Deparunent of Geology, University of Otago. Unpublished. I

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