Floristics and structure of mire-forest ecotones, west coast South Island, New Zealand

Abstract

Two ecotones between a raised ombrogenous mire and forest on the west coast of the South Island, New Zealand, were investigated. Changes in floristics across the first ecotone parallel changes in the underlying sediments and peat depth. The mire appears to be located in an old river channel and may not have changed greatly in extent since it was formed. Contrary to some other studies of west coast, there was no evidence for forest invasion of the mire; indeed the forest was apparently unable to establish on the raised area of the mire. The vegetation sequence in the second ecotone appears superficially to represent mire invasion of forest. However, there were large dead tree stumps, presumably Dacrydium cupressinum, and abundant D. cupressinum regeneration, which suggest that this area is more likely to be going through normal D. cupressinum regeneration processes. Pronounced structural boundaries observed in both ecotones may represent old fire boundaries. I conclude that the position of the mire-forest ecotone is relatively stable, because it is determined by the underlying sediments, but that the floristics and structure of the ecotones themselves are dynamic, and respond to a variety of disturbance process including fire and stand replacement.

Keywords:

• ombrogenous mire
• vegetation dynamics
• fire
• vegetation change
• Dacrydium cupressinum