ACCURACY OF TREE GROWTH MEASUREMENTS USING DENDROMETER BANDS

Dendrometer bands are commonly used to make repeated measurements of tree circumference despite their tendency to underestimate first-year growth. Underestimates of growth are generally attributed to slack remaining in the bands after installation. To test for first-year measurement errors, 60 trees were fitted with a second dendrometer band 2 years after installation of the first band. The new bands consistently showed significantly less growth than the old bands (old-band measurements were assumed to represent true growth). Regression equations were developed to relate new-band estimates to true growth. There were no significant differences in regression intercepts for the three tree species tested, but significant differences in regression slopes were detected. Comparisons between canopy and subcanopy trees and between angiosperm species (Nyssa aquatica L. and Nyssa sylvatica var. biflora (Waiter) Sargent) and a gymnosperm (Taxodium distichum (L.) Rich.) explained 95.7% of the variance in regression slopes for the individual species. It appears that in addition to band slack, part of the first-year error in dendrometer band data may result from species differences that are related to bark and stem characteristics.