Structure and Composition of New Zealand Beech Forests
Seen from either the inside or the outside, pure beech forest in New Zealand has a very different appearance from conifer broadleaf forest. Externally (Fig. 71
), for example when viewed on the steep side of a mountain valley, beech forest has a uniform, generally dark green colour and a smooth to moderately uneven surface. There are no emergent j trees. There is none of the tangled profusion of the conifer broadleaf
Figure 72 (opposite) Interior of red beech (Nothofagus fusca) and silver beech (N. menziesii) forest near the Maruia Saddle, South Island. Photo: J. H. Johns.
forest within the beech forest (Fig. 72
), particularly when rainfall is moderate or low. There are clearly fewer species present and because of the sparse undergrowth and absence of vines, one can walk freely among the rough-barked trunks. Vascular epiphytes too are generally absent, although there are often epiphytic mosses and lichens on the trunks and branches. The forest floor has a deep carpet of leaf litter, soft cushions of the pale green milk moss (Leucobryum candidum
) and masses of the translucent fans of the kidney fern (Trichomanes reniforme
). Among the scattered shrubs which may be present, the small leaved Styphelia
) fasciculata, S. juniperina
(soft and prickly mingi-mingi respectively), Coprosma rhamnoides
and C. microcarpa
are most frequently encountered. Light filtering through the attractive layers of the beech foliage contributes to the typically tranquil, orderly atmosphere of this type of forest. Beech forest becomes more complex with higher rainfall, as on the west of mountains at higher altitudes. Its growth appears more luxuriant, largely as a result of the profusion of lichens, mosses, liverworts and moss-like filmy ferns clothing the forest floor and trunks and branches of the trees. Where the canopy is partly open there are also more species of small trees and shrubs involved although none is restricted to beech forests. Broadleaf (Griselinia littoralis
)Pseudopanax simplex, Coprosma foetidissima
and others may contribute to a subcanopy and there is often a shrub layer of small-leaved coprosmas, the smallleaved Myrsine divaricata,
the mountain horopito (Pseudowintera colorata
) and others.
Larger ferns on the forest floor include the well-known crepe fern or Prince of Wales Feathers (Leptopteris superba) and Blechnum discolor. Two small flowering plants growing in moss cushions are characteristic of this type of forest — Luzuriaga parnflora with spreading wiry stems, two-ranked leaves and large spongy white berries, and Libertia pulchella with half erect fans of grasslike leaves.
These wet beech forests in New Zealand are sometimes swathed in mist; forests of a similar character elsewhere in the world are often referred to as cloud or mossy forest, or more romantically 'goblin forest' or 'elfin woodland'.
At the other extreme, some of the beech forests in relatively dry sites on the east of the South Island mountain axis are among the simplest of forests anywhere, consisting of virtually a single species — mountain beech.
As a generalisation, where there is a trend away from mild, moist conditions and fertile soils towards cooler or drier conditions and less fertile soils, or combinations of these, there is often a transition from conifer broadleaf to beech forest.