SUSTAINABILITY OF BEILSCHMIEDIA-TAWA-DOMINATED FOREST IN NEW-ZEALAND - POPULATION PREDICTIONS BASED ON TRANSITION MATRIX MODEL ANALYSIS

Beilschmiedia tawa (Lauraceae) is a common canopy tree which is often dominant in lowland forests in the North Island and northern South Isl and of New Zealand. The sustainability of B. tawa-dominated forests wa s investigated at Pureora Forest Park, west of Lake Taupo, central Nor th Island, where a range of sites with different extents of disturbanc e by logging was studied. Demographic studies-estimates of seedfall, r ecruitment, growth, and mortality rates-yielded data for life history tables. Based on these, Leslie matrix models were used to determine th e rate of increase of five populations. Of these, three logged populat ions were apparently declining, whereas unlogged forest showed moderat e population increase. These population studies suggested that B. tawa is a K-selected species capable of regeneration only within forest. T he smaller size-classes are shade tolerant and stems accumulate in the stripling size-class. High light conditions are needed for growth fro m this class to the sapling class.