An Automated Instrument for the Measurement of Bark Microrelief

Bark microrelief is of importance to the physiological ecology of forested ecosystems because it has been documented to influence the distribution of corticolous lichens, stemflow generation, and forest biogeochemical cycles. Hitherto no instrument existed to characterize the inherent variability of bark microrelief with high spatial resolution. Our newly designed prototype instrument consists of a hinged ring, laser rangefinder, and motor linked to a standard laptop. The prototype produces trunk cross sections at a 0.33 degrees horizontal resolution and detects bark-ridge-to-furrow heights at < 1 mm resolution. The prototype was validated by comparing measurements of bark microrelief between the instrument and digital calipers. The mean absolute error of the prototype as a percentage of the measured average microrelief was 1.0%, with a mean absolute error of 0.83 mm. Our bark microrelief prototype instrument can supply critical requisite information of bark microstructure that can be used by researchers to interpret the distribution of lichens and bryophytes on tree surfaces, relate stemflow yield and chemistry to bark microrelief, and provide detailed measurements of the changes of bark microrelief with stem dehydration. In short, the prototype instrument can be used to gain a more holistic understanding of the physiological ecology of forest ecosystems.