Development and evaluation of a new type of opto-electronic dendrometer

Abstract

A new type of dendrometer, comprising two reflection type photointerruptors and flexible mirrors, was developed to record precisely the diameter changes of tree trunks, and the practicality of this device was examined. The maximum resolution of the detector was 600 nm, due to the quantization noise of A/D conversion. Measurement in the laboratory at a constant temperature demonstrated fluctuations in the output of only three bits of A/D conversion, corresponding to a change of c. 3.6 μm in diameter. There was no thermal drift of the device during measurements. Diameter changes of sapling stems and/or a tree trunk of Castanospermum australe (Leguminosae) and Zelkova serrata (Ulmaceae) were measured by this device. In addition to steadily thickening growth and diurnal diameter changes, all the plants showed spike-like diameter changes of the order of minutes, the discovery of which illustrates the superior performance of this new type of dendrometer.