Sustainability of Beilschmiedia tawa-Dominated Forest in New Zealand: Population Predictions Based on Transition Matrix Model Analysis

Abstract

Beilschmiedia tawa (Lauraceae) is a common canopy tree which is often dominant in lowland forests in the North Island and northern South Island of New Zealand. The sustainability of B. tawa-dominated forests was investigated at Pureora Forest Park, west of Lake Taupo, central North Island, where a range of sites with different extents of disturbance by logging was studied. Demographic studies-estimates of seedfall, recruitment, growth, and mortality rates-yielded data for life history tables. Based on these, Leslie matrix models were used to determine the rate of increase of five populations. Of these, three logged populations were apparently declining, whereas unlogged forest showed moderate population increase. These population studies suggested that B. tawa is a K-selected species capable of regeneration only within forest. The smaller size-classes are shade tolerant and stems accumulate in the stripling size-class. High light conditions are needed for growth from this class to the sapling class.