Abstract Detail

Bryological and Lichenological Section/ABLS

Gutman, C.H. [1], Rice, S.K. [1], Krouglicof, N. [2].

Laser scanning reveals variation in bryophyte canopy structure.

In bryophytes, canopy structure influences the exchange of matter and energy with the environment. Measurement of canopy structure has relied on canopy depth data provided by 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. Laser scanners measure surface features in three dimensions remotely by introducing a plane of light onto the surface. Coordinates along the canopy-light intersection are found using triangulation on an image captured with a CCD camera placed a given angle from the light plane. We evaluated the potential of laser scanning to quantify variation in bryophyte canopy structure. Moss and liverwort canopies with diverse morphologies were collected from northern bog and boreal forest communities in New York State. Canopy depth profiles were measured using a contact probe, an LED based scanner developed for the project, and a commercial laser scanner. Surface roughness height (L_r), a parameter that summarizes variation in canopy depths, was calculated from each data source and compared. Surface roughness heights measured with the LED and laser scanners were linearly related to roughness heights measured with the contact probe. However, L_r values from the laser scanner were lower than L_r derived from the contact probe due to an inability of the scanner to detect surfaces deep within the canopy. This pattern was not evident in the LED scanner as the triangulation angle was adjusted to optimize depth penetration. LED scanning did not impose physiological stress assessed using chlorophyll fluorescence (Fv/Fm) in dark adapted samples of Sphagnum girgensohnii, Bazzania trilobata and Pleurozium schreberi. Specimens (n = 4) were exposed to either high light, LED scanning or low light. In each species, Fv/Fm did not differ between scanned samples and controls, whereas Fv/Fm was reduced in samples exposed to high light.

1 - Union College, Biological Sciences, Schenectady, New York, 12308, USA
2 - Union College, Mechanical Engineering, Schenectady, New York, 12308, USA

Keywords:
chlorophyll fluorescence
surface roughness
light stress
Sphagnum
Bazzania
Pleurozium.

Presentation Type: Paper
Session: 51-3
Location: Magpie (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 1:30 PM
Abstract ID:783