Use of thin sections to improve age estimates of Nothofagus pumilio seedlings

DANIELS, L.D.; VEBLEN, T.T.; VILLALBA, R.

ECOSCIENCE (SAINTE-FOY)

Université Laval

Lugar: Montreal; Año: 2007 vol. 14 p. 17 - 22

1195-6860

This paper reports the use of thin-sections to improve precision and accuracy when aging seedlings of Nothofagus pumilio (Poepp. & Endl.) Krasser. We compare two methods for determining the number of rings on 85 basal disks from seedlings: (1) ring counts of wood disks viewed with reflected light, and (2) ring counts of thin-sections viewed with transmitted-light. Samples included 14 to 53 rings. Comparison of ring counts from the two methods revealed discrepancies of 1 to 12 years for 85% of the seedlings. Two sources of error were identified. In 70 of 85 samples, up to 12 incomplete rings explained differences between ring counts of two radii on the same wood disk. Secondly, the small radii, large number of rings, and diffuse porous nature of the wood resulted in frequent errors when visually detecting rings on wood disks. One to three false rings were detected in 15 seedlings. Narrow and suppressed rings in 57 samples resulted in under-estimates of 1 to 12 years for ring counts on wood disks relative to thinsections. Visual crossdating of thin-sections allowed us to identify false and incomplete rings, improving precision and accuracy when determining seedling age. For studies of slow-growing seedlings that require annual or quasi-annual resolution of age estimates, we recommend the preparation and dating of thin-sections as outlined in this paper.