Primary succession in Westland National Park and its vicinity, New Zealand

Abstract

This paper concludes a series on the vegetation of Westland National Park with an outline of the development of vegetation on new surfaces. A particularly long succession, well dated over its latest 14 000 years, is taking place on surfaces formed during the fluctuating retreat of low-altitude glaciers. Surfaces have been classed as gravel slopes, alluvial flats, loose boulders, solid bedrock, landslide scars, and talus slopes. In general, they show a development from open pioneer vegetation, through shrubland and seral forest to “climax forest”, and eventually, a deterioration to heathland vegetation where soils change to gley podzols with impervious iron pans. On poorly drained areas, successions lead to infertile swamps.

Successions at subalpine and alpine levels are slower and none in the district are older than the end of the last major glaciation. Consequently, they do not reach a stage equivalent to the low-altitude heathlands, except where the former glaciers left scoured bedrock that is still almost bare of soil.

Nothofagus menziesii has entered the south-eastern part of the Park, apparently late in post-glacial time. Its rapid colonisation of new surfaces contrasts both with its very slow marginal invasion of other forest communities, and with the delayed entry of native conifers into primary successions where beech is absent.

Keywords:

• primary succession
• Westland, New Zealand
• altitudinal sequence
• gley podzol
• forest
• heathland
• Nothofagus menziesii