Ecological studies of a marine terrace sequence in the Waitutu Ecological District of southern New Zealand. Part 1: The vegetation and soil patterns

This paper presents quantitative descriptions of the vegetation plus associated vascular flora and soils on a sequence of ten marine terraces that extend from a Holocene raised beach a few metres above sea level to a terrace remnant at an elevation of 630 m some 12 km inland. From the floristically rich coastal turf and scrub that occupies the most recent terrace there is a distinct sequence of vegetation. Tall mixed silver beech-podocarp-broadleaved forest on the lower altitude terraces (Terraces 2,to 4, < 150 m elevation) grades via mixed mountain beech-podocarp-manuka woodland through shrubland to open bog on the five terraces above 250 m. A postulated long-term, uninterrupted soil-vegetation chronosequence has not been confirmed. Soil development has been strongly affected by devegetation and surface deflation under periglacial conditions, and differential accumulation of loess during Pleistocene glacial periods. It is concluded that the vegetation pattern is related to a range of soil factors, particularly gradients in profile wetness that are associated with the increasing elevation between terraces and minor differences in topography within terraces. The sequence provides an extensive, essentially unmodified and valuable soilvegetation complex representative of marine terrace ecosystems formerly of widespread distribution nationally, which justifies formal reservation.