Tree productivity models based on annual ring widths for contemporary and subfossil scots pine in Ireland.

Abstract

Ring width series from Pinus sylvestris L. are used to compute empirical growth functions for a number of sites, including two subfossil pinewood sites. These empirical functions are corrected for non-proportionality of annual ring width and stem volume increment. Significant correlations between stem diameter and tree productivity allow the corrected curves to be interpreted as current, mean tree productivity on each site. The trends evident in the productivity curves correspond with reported changes in pine productivity with age. A comparison of relative productivity on the sites sampled indicates that trees growing on mineral substrates achieve higher current annual production than trees growing on peat at all ages. The rate of increase is also greater, and maximum productivity is achieved in older trees on mineral soils. Minimum relative productivity occurred in subfossil pines which grew on a midland raised bog. The observed differences in productivity are primarily attributed to differences in soil nutrient status and drainage. It is suggested that productivity curves might be used in conjunction with information on stand density, and calibrated with quantitative productivity data to yield estimates of absolute stand productivity. This would be particularly useful in the study of subfossil woodlands where direct measurements are not possible.