Late Holocene forest disturbance in Gisborne, New Zealand: A comparison of terrestrial and marine pollen records

Abstract

A late Holocene (from c. 5500 yr B.P.) record of vegetation change is presented for the Gisborne region, based on pollen, charcoal, and tephra analyses of a terrestrial and a marine core. Up until the time of anthropogenic deforestation about 650 yr B.P., well drained lowland areas were covered with a Prumnopitys taxifolia, and Dacrydium cupressinum‐dominated podocarp/hardwood forest. The poorly drained Dacrycarpus dacrydioides‐dominated alluvial swamp forests were not as vulnerable to fire, and remained on the Gisborne Plains until European drainage and clearance began in the 19th century. In the last 5500 yr B.P., the lowland forests have been disturbed by at least five ashfalls originating from volcanic eruptions in the Central Volcanic Region. Where the terrestrial and marine cores overlap, comparisons of the pollen records show the vegetation changes and taxa present to be comparable. The fire record was not clear in the marine record, as the charcoal curve was diluted with high background levels of reworked charcoal. Sedimentation rates from the marine core indicate tha erosion in the Waipaoa catchment has increased significantly since European clearance of soil‐protecting remnant forest and fern/scrubland and its replacement with pasture.

Keywords:

• charcoal
• deforestation
• disturbance
• El Nino
• fire
• human impact
• New Zealand
• pollen
• Poverty Bay
• tephra
• vegetation history
• volcanism