Beech-Hardwood Forest Composition, Landforms, and Soil Relationships, North Westland, New Zealand

• Published in: Vegetatio 1993-05, Vol.106 (2), p.111-125
• Main Authors: Stewart, G. H., Basher, L. R., Burrows, L. E., Runkle, J. R., Hall, G. M. J., Jackson, R. J.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Coniferous forests; Forest communities; Forest soils; Fundamental and applied biological sciences. Psychology; Landforms; Nothofagus; Peat soils; Pedogenesis; Soil composition; Soil plant interactions; Soils; Synecology; Terraces; Terrestrial ecosystems
• ISSN: 0042-3106
• DOI: 10.1007/bf00045065

The relationships between forest composition, landforms, and soils were examined in a 2 km⁲ region of river terraces and lower hill slopes on Mt Harata, in north Westland, New Zealand. Ten forest communities were classified from 197 vegetation descriptions using TWo-way INdicator SPecies ANalysis (TWINSPAN). Landforms were classified at all vegetation sample sites using a hierarchical system, and brief soil descriptions were made at 70% of sites. Compositional gradients and their relationship to environmental variation were investigated by detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA). On terraces and fans changes in forest composition were closely related to differences in soil drainage and stage of soil development (functions of surface age, slope, and stability). On recent terraces and well-drained terrace risers, recent and weakly developed yellow-brown earth soils supported beech forest communities characterised by Nothofagus fusca, but on poorly drained older terrace surfaces, well developed gley and peat soils predominated under Nothofagus solandri var. cliffortioides forest. Compositional variation on the hillslopes was broadly related to stage of soil development on different landforms, but relationships were more difficult to detect because of the influence of increasing altitude and tree uprooting, which interrupted soil pedogenesis and promoted the regeneration of even-aged Nothofagus truncata-hardwood stands. Our results confirm the observation that disturbances such as landsliding and windthrow rejuvenate the soil whereas stability leads to old, infertile, and often poorly-drained soils. The compositional variation across different landforms therefore reflects variation in the magnitude and frequency of disturbances. The predominance of windthrow and general lack of landsliding at Mt Harata also suggests that the disturbance regimes of these forests may be different from those of the conifer-broadleaved hardwood forests of central Westland.