Late Pleistocene and Holocene vegetation history, Central Otago, South Island, New Zealand

Abstract

Pollen diagrams from upland blanket bogs and mire‐pool complexes on the southern Garvie Mountains and the Old Man Range, and from a sag pond mire on the slopes of the Kawarau Gorge, record the vegetation history of the last 12 000 years in Central Otago, the driest region of New Zealand. During the late‐glacial/early Holocene these subalpine sites supported grassland/shrubland vegetation. Trees or tall scrub were absent. Tree ferns became increasingly common in the early Holocene, most likely as small stands in damp, sheltered locations. At 7500 yr B.P. a coniferous forest of Prumnopitys taxifolia, Dacrycarpus dacrydioides and Podocarpus abruptly replaced the previous grassland communities at lower altitudes, while a coniferous scrub of Phyllocladus alpinus and Halocarpus bidwillii formed the upper treeline. The reafforestation of Central Otago and adjacent regions was completed 2000 years after podocarp‐dominant forest began to occupy coastal regions. The delay is attributed to drier climates in the interior of the southern South Island during the early Holocene. From 6000 yr B.P. Nothofagus menziesii began to spread through the higher altitude forest, and shortly after 3000 yr B.P. N. fusca type forest began to replace the previous treeline dominants, Phyllocladus and Halocarpus. Treeline may have risen slightly in the mid to late Holocene. From 600 yr B.P., repeated fires destroyed both lowland and upland forest and tall scrub communities. First bracken, and then grassland, replaced the burnt forest. These fires were a consequence of Maori exploitation of the Otago hinterlands.