Distribution of native forest in the upper Clutha district, Otago, New Zealand

The upper Clutha district extends from steep, glaciated mountains along the South Island Main Divide to broad plateaus and terraced valleys further do wnstream, and covers an annual precipitation gradient from 4000 mm to 400 m m. Tall forest prevails from the valley floors to the subalpine tree limit in north-western headwaters, but southwards down the rainfall gradient beco mes increasingly confined to small pockets. Nothofagus is overwhelmingly do minant, with N. menziesii prevailing in the north-west and N. solandri var. cliffortioides in drier country to the east. Pockets of forest in the sout h of the district can consist of either species. Nothofagus fusca co-domina tes with the other Nothofagus species at low altitudes through part of the Matukituki catchment, and over a small area by Lake Hawea. Low-altitude N. menziesii forest in the Makarora Valley has a similar composition to forest s west of the Main Divide, and includes several conifer species and a wide range of broadleaved trees, notably Weinmanni. a racemosa. The hardiest con ifers, Podocarpus hallii and Phyllocladus alpinus, are widely distributed i n the Nothofagus forests of the district and also dominate small stands of native trees on otherwise treeless mountains. In the moister part of the di strict Kunzea ericoides and Leptospermum scoparium are successional to broa d-leaved forest, whereas in the drier parts they are self-perpetuating. Gre y scrub, dominated mainly by Discaria toumatou, is widespread on slopes whe re rainfall is low, and on river flats under higher rainfall. Small trees o f Sophora microphylla and Olearia spp. occur locally in this scrub.