Comparison of altitudinal sequences of vegetation on granite and metasedimentary rocks in the Preservation Ecological District, southern Fiordland, New Zealand

Abstract

Vegetation and soils were sampled along paired altitudinal sequences on granite and adjoining metasedimentary rocks from sea level to treeline at approximately 900 m elevation at Dusky Sound, Fiordland. Soils derived from granite are less fertile, and are inferred to provide less rooting volume than those on metasediment. Nothofagus menziesii alone dominates the continuous tall forest on metasediment; in the forest on granite, four or more species form the canopy. On granite, treeline is depressed by 150 m, and shrubland and grassland alternate on mineral soil and peat respectively, at altitudes supporting N. menziesii forest 11 – 15 m tall on metasediment. Total species richness and density of woody stems are greater on granite, but mean tree basal area is consistently less than that on metasediment. The dominance/diversity models tested indicate that community structure changes with altitude in different ways on the two substrates, a pattern that is difficult to explain until we know more about the influence of the environment on dominance/diversity relations.

Keywords:

• plant communities
• granite
• dominance and diversity
• New Zealand