Laser scanning reveals bryophyte canopy structure.

We evaluated laser scanning as a method to provide depth measurements for bryophyte canopies at fine spatial scales to derive surface roughness (Lr), a structural parameter. Depths to the first vertical canopy contact were measured on 5 x 5 cm2 areas of 27 bryophyte canopies using a contact probe, a commercial laser scanner and a scanner employing a laser diode striper (LED scanner). Laser scanning adequately distinguished structural types, but scanner configuration led to differences in the magnitude of Lr. LED scanning did not damage photosystem II function in three bryophyte species, Bazzania trilobata, Sphagnum girgensohnii and Pleurozium schreberi, as evidenced by no change in the chlorophyll fluorescence parameter FV/FM following LED scanning, but a decrease when subjected to high light. A previously published boundary layer conductance model was parameterized with surface roughness values determined using a laser scanner and compared with the results obtained with contact probe measures. The resulting parameters of the functional models did not differ significantly from each other.