POPULATION-DYNAMICS OF THE NIKAU PALM, RHOPALOSTYLIS-SAPIDA (WENDL-ET-DRUDE), IN A TEMPERATE FOREST REMNANT NEAR AUCKLAND, NEW-ZEALAND

Survival, growth rate and fecundity are described for a population of the New Zealand nikau palm, Rhopalostylis sapida, based on six years of data for survival and growth, and seven years of data for fecundity. Transition matrix analyses were compared for height-classified (size) and frond scars-classified (approximate age) life-tables. Estimates of 1.004 (height), and 1.007 (scars), were obtained for the finite rate of increase, suggesting that this population is a numerically stable component of the temperate forest in which it is found. Nevertheless, differences between the initial and stable stage distributions, especially for the height-classified analysis, indicated that the present population size structure was not consistent with the measured rates of growth and survival. Specific disturbances over approximately the last 30-40 years may account for these differences. Measures of sensitivity, elasticity, and selective pressure revealed that the high survival rate for palms in the mature and immediately pre-reproductive stages had the strongest influence on population growth rate. Faster growth through the seedling and juvenile stages would also markedly increase population growth rate. Population growth rate was relatively insensitive to changes in fecundity. R. sapida shows similar life history properties to several tropical palms, and other long-lived tree species in general.