FOREST PERSISTENCE AT COASTAL WAIKATO, 24000 YEARS BP TO PRESENT

Two sites on the western Waikato coast were investigated by pollen ana lysis. Airstrip Bog (alt. 135 m) contained an unbroken record of Late Otiran vegetation from >23 400 +/- 340 years BP to <16 050 +/- 180 yea rs BP. Cold wet conditions existed between 25 000 and 20 000 years BP. Subalpine shrubs grew on the bog and at least two species of Nothofag us on the surrounding hills. Low temperatures with increasing aridity followed, and the bog flora was much reduced. After 17 200 years BP it became warmer and wetter; Nothqfagus extended its range. Throughout t he last 10 000-year record, coastal lowland species including Ascarina contributed pollen to the spectrum. Deep Hole, the second site (2 m a .s.l.), records the existence of a lagoon developed behind a rock sill subsequent to the high Holocene sea level c. 6500 years BP. Drainage of the lagoon occurred about 2610 years BP, and the site passed throug h seral changes until these were interrupted by human intervention. Fu scospora pollen was tentatively identified as N. truncata. Agathis pol len was found only at Deep Hole and only in European times (past 150 y ears). This study provides the first information on the late Pleistoce ne vegetation of coastal Waikato and shows the continuity of forest at low altitudes through glacial times. It establishes the presence of t wo species of Nothofagus and indicates that N. truncata was present in the vicinity of both sites. The study supports other work indicating Agathis was still advancing southwards in the past 150 years.