On the diameter growth rates of red beech (Nothofagus fusca) in different parts of New Zealand
- Department of Biogeography and Geomorphology, Research School of Pacific Studies, The Australian National University, Canberra, Australia
The relationships between age and diameter for red beech (Nothofagus fusca) at six sites in the South Island and on Mt Colenso in the North Island of New Zealand are illustrated and discussed. Red beech trees of one diameter varied in age by up to 150 years, but in anyone area the correlation between age and diameter was significant. The coefficient of slope of the linear regressions of age on diameter ranged from 1.0 to 3.0 years/m. The maximum longevity of the species was c. 500 years. Plotting the mean altitudes from which the samples were obtained against their mean growth rates revealed a steep and significant trend. The maximum average (between trees) growth rate was c. 1.0 m/year for stands at the lower limit of the species, falling by c. 0.076 m/year for every 100 m of altitude gained. These growth rate relationships are compared with data from other species of Nothofagus, in particular N. menziesii. It is suggested that if growth rate is taken to be a component of the competitive balance between these two species, this balance varies continuously with altitude, red beech gradually losing its advantage as it ascends. The struggle for dominance may occur in the seedling and sapling stages following colonisation of limited microsites by seedlings of both species.