Provenance variation in the New Zealand species of Nothofagus

Provenance variation was studied in the growth and morphology of seedlings of silver beech (Nothofagus menziesii), red beech (N. fusca), hard beech (N. truncata), black beech (N. solandri var. solandri), and mountain beech (N. solandri var. cliffortioides). Seedlings were grown for 2½ years in replicated provenance experiments at Rangiora and Rotorua. Silver beech was shown to be a genetically variable species, with strong differentiation into regional ecotypes and possibly altitudinal clines. North Island provenances from lower altitudes grew the fastest and had the biggest leaves. Exceptionally small leaves, which turned a claret red in winter, were a feature of two low-elevation provenances from Westland. Red beech seemed a comparatively uniform species, with only minor genetic variation apparent in the growth rate and appearance of seedlings from a comprehensive range of provenances. Hybridism with N. solandri was prevalent in several seedlots. Hard beech was poorly represented in the study. At Rotorua, the local Mamaku Plateau provenance was the most vigorous, but was the slowest-growing at Rangiora. In the black beech - mountain beech complex there was considerable provenance variation in the size, shape, colour, and arrangement of leaves, as well as in the branching habit and growth rate of seedlings. Clinal genetic variation in seedling growth rate was demonstrated in a series of altitudinal provenances of mountain beech from the Craigieburn Range, Canterbury. Seedlings of black beech grew faster than those of mountain beech, had a characteristic interlacing habit, with distant, orbicular leaves, and were partially deciduous in winter. A third form of N. solandri was recognised, with seedlings in many ways intermediate between those of mountain beech and black beech. These undifferentiated populations of N. solandri occur on well-drained, low-altitude sites in the South Island. The seedlings are of erect habit, have relatively large leaves, and are among the fastest-growing of all the New Zealand beeches.