Laser scanning provides a novel approach for accessing bryophyte canopy structure

Claudia Gutman

Department of Biological Science

Union College, Schenectady, NY

ABSTRACT

In bryophytes (i.e., moss and their relatives), canopy structure influences light extinction, water fluxes, carbon uptake and productivity. Despite the need to evaluate canopy structure, quantifying surface features has proven problematic. Previously, measurement techniques relied on surface contact probes. This approach is laborious, offers low-resolution data sets, and is inadequate for use in the field or for characterizing large surfaces. This study demonstrates that laser scanning can be used to quantify fine details of bryophyte canopies. Live Bazzania trilobata, Callicladium haldanianum, Campylium chrysophyllum, Dicranum scoparium, Hylocomium splendens, Leucobryum glaucum, Pleurozium schreberi, Polytrichum commune and Sphagnum fuscum individuals from forested habitats in New York State were sampled using a contact probe and an LED based scanner developed for the project. Samples were then lightly painted to increase reflectance and sampled with a commercial laser scanner. Surface roughness height, a parameter that describes variation in canopy depth measures, was calculated from each data source and compared. Surface roughness heights measured with the LED and laser scanners were both predictably related to roughness heights measured with the contact probe. However, surface roughness heights determined by laser scanning had a lower magnitude due to an inability to detect structures deep within the canopy. Scanning did not impose physiological stress as assessed with the chlorophyll fluorescence measure F_v/F_m in dark adapted Bazzania trilobata, Pleurozium schreberi and Sphagnum girgensohnii samples. Consequently, LED scanning may be used for physiological studies on live specimens.