Using fibre-optic sensing for non-invasive, continuous dendrometry of mature tree trunks

Dendrometry is the main non-invasive macroscopic technique commonly used in plant physiology andecophysysiology studies. Over the years several types of dendrometric techniques have been developed,each with their respective strengths and drawbacks. Automatic and continuous monitoring solutionsare being developed, but are still limited, particularly for non-invasive monitoring of large-diametertrunks. In this study, we propose a new type of automated dendrometer based on distributedfibre-optic sensing that continuously measures the change in stem circumference, is non-invasive, andhas no upper limit on the trunk diameter on which it can be installed. We perform a three-monthvalidation experiment during which we deploy a fibre-optic cable at three localities around thetrunks of two specimens of Brachychiton. We verify the accuracy of this new method throughcomparison against a conventional point-dendrometer, and we observe a consistent time lag betweenthe various measurement locations that varies with the meteorological conditions. Finally, we discussthe feasibility of the fibre-based dendrometer in the context of existing dendrometric techniques andpractical experimental considerations.