REGENERATION DYNAMICS OF ALLUVIAL GAPS IN A WARM TEMPERATE RAIN-FOREST IN NEW-ZEALAND

Gaps formed by stream laid gravels in a warm temperate Podocarp-Angios perm rain forest in New Zealand were quickly invaded by 41 free-standi ng woody species. Height-age curves for the eight most frequent specie s were used to construct a 12 yr chronosequence which showed 18 specie s arrived by 0.9 yr and 33 by 1.9 yr. This rapid invasion was supplied from both gaps and mature forest and fitted the Initial Floristic Mod el coupled with a Facilitation Mechanism. Over the 12 yr period, stem density and births peaked at 0.9 yr and deaths at 1.9 yr with a natali ty of 39.5/m2, a mortality of 38.5/m2 and nearly 99% dying as seedling s. Plant height increased to 5.1 m at 12.1 yr with height increment pe aking at 43 cm/yr at 7.3 yr. Maximum potential heights ranged from 4 t o 60 m and were positively correlated with longevity which varied from 20 to 1150 yr for 19 known species. A decline in height increment to 0.9 yr showed a below-ground component in intraspecific competition wi th significant negative correlations between stem density and height i ndicating a later above-ground component. There was no significant hei ght competition amongst the 11 most frequent species and only one sign ificant negative interspecific association. This suggests high species coexistence for which 'Equal chance' was probably the major mechanism . Given this coexistence, rapid species arrival, early sexual maturity and similar density and height-age patterns, the main dynamic variabl es may be maximum height, longevity and height increment, all of which are, partly, genetically programmed. Most dynamic affinities are with tropical forest, although height growth and species richness are warm temperate.