Vegetation of a coastal sand dune system in southern New Zealand

Abstract

The introduction of vigorous exotic species has destroyed much of the native sand dune vegetation along the coasts of South Island, New Zealand. However, some dunes built by the native cyperad Desmoschoenus spiralis still remain in the southwest.The dunes at Cole Creek, on the West coast of South Island, were chosen as a relatively pristine study area. 15 transects were laid through semi‐fixed dunes into dwarf forest. Environmental measurements were taken at regular intervals through the dunes: pH, soil moisture, organic matter, conductivity, nutrient status and elevation. Classification and ordination of these data demonstrated that two major environmental areas were present ‐ open dune and dwarf forest ‐ with an abrupt ecotone between them. Vegetation analyses revealed a loosely‐banded pattern, parallel to the sea. Vegetation types with few but constant species such as Desmoschoenus spiralis and Calystegia soldanella, predominated in the open dune. Forest species were rarely found seaward of the dune/forest boundary, though there was evidence the Spatial Mass Effect was operating.Multiple regression and canonical correlation of the vegetation and environmental factors showed that the main factors affecting vegetation patterns were the environmental complex related to distance from the sea, elevation above mean tide, soil alkalinity and moisture.