New Zealand Journal of Botany abstracts

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Dendroecological studies in New Zealand 1. An evaluation of tree age estimates based on increment cores

D. A. NORTON

School of Forestry, University of Canterbury
Private Bag, Christchurch, New Zealand

J. G. PALMER
J. OGDEN

Department of Botany, University of Auckland
Private Bag, Auckland, New Zealand

Abstract Tree-ring counts from increment cores are widely used in ecological studies for determin- ing tree ages. In New Zealand many canopy trees are slow-growing and long-lived, and have extremely narrow rings. Single rings or groups of rings may be absent on some radii. Such narrow and absent rings cause difficulties in ring counting and necessitate careful sample preparation. The errors associated with age estimates derived from cores which do not reach the chronological centre of the tree (partial cores) are discussed. Four partial core lengths and three methods of estima- tion were used on cross-sections of known age from Agathis australis, Libocedrus bidwillii, Nothofagus solandri, and Prumnopitys taxifolia. It is concluded that mean errors may be less than +10% where the core length represents 90% of the geometric radius (half the measured diameter) but increase with shorter cores. However, much greater errors may apply to individual estimates, up to ± 78% in one case. Moreover, the direction of the error (above or below the true value) is largely depend- ent upon the early growth conditions and is unpre- dictable. These errors appear to occur for three main reasons: eccentric growth, age dependent growth variations, and other growth variations.

Keywords dendroecology; tree-age estimates; population dynamics; growth rings; tree growth; dendrochronology

Received 13 June 1986; accepted 12 September 1986
New Zealand Journal of Botany, 1987, Vol. 25: 373-383
0028-825X/87/2503-0373$2.50/0 © Crown copyright 1987

PDF file of entire paper: medium quality (813K); (scanned from paper original: notes about this process)

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