|
Methods:
Structural Analysis |
*Purpose: To compare surface roughness heights determined with the LED
scanner to the valuesderived from the contact probe |
| Species Investigated |
| Callicladium haldanianum |
| Campylium chrysophyllum |
| Dicranum scoparium |
| Hylocomium splendens |
| Leucobryum glaucum |
| Pleurozium schreberi |
| Polytrichum commune |
| Sphagnum fuscum |
| Bazzania trilobata |
|
Photo of boreal forest fieldsite in Essex
County, NY
|
°All
species were collected from forested habitats in Otsego and Essex counties in New York
State during October 2003
|
|
|
|
Contact Probe
Approach |
(click here to see contact probe apparatus) |
Measurement Procedure:
1) Canopy depths for a
5 x 5 cm area were measured at a minimum sample scale of 0.1 cm for a total of 223 sample
points per canopy.
|
| 2)
Canopy depths were detrended and subject to semivariance analysis |
°Semivariance describes
the average squared differences in depth at a given sampling scale (lag). When
semivariance is graphed as a function of lag, semivariance typically increases with lag to
a maximum value and then plateaus.
|
3) Roughness height (Lr), a parameter
defined previously by Rice et al. (2001), was calculated as the square root of
twice the maximum semivariance.
|
Sample semivariance analysis
for Pleurozium schreberi
Max. semivariance = 24.2
Lr = 6.96 mm
|
 |
|
|
|
LED Scanning
Approach |
(click here to see LED scanning apparatus) |
Measurement procedure:
1) A 5.0 x 6.5 cm area of each canopy was scanned
at a sample scale of 2.0 mm in the x-direction, resulting in a maximum of 10,920
depth points2) For each image, a computer program designed for the project
was applied to:
a) Identify the LED stripe
b) Transform (flatten) the image to correct for lens distortion
c) Derive x, y, z coordinates for each point
3) Derived points were then converted to the roughness index, Lr |
Sample semivariance analysis
for Pleurozium schreberi
Max. semivariance = 15.9
Lr = 5.64 mm
|
 |
|
|
|
|
Laser Scanning
Approach |
(click here for the laser scanning appraatus) |
Measurement Procedure:
1) Light
absorption in live bryophytes rendered the laser scanner unable to detect surfaces of live
plants. To increase reflectance from the canopy surface, samples were lightly painted with
a commercial flat white spray paint (#1520 Krylon paint, Sherwin-Williams, Cleveland, OH).
This resulted in a 23 µm coating, which is smaller than the accuracy of the scanner. 2) A 3 x 3 cm area of each canopy was scanned
with a Replica 3D scanner with Reversa 25
optics hardware, resulting in a maximum of 13,077 depth points.
3) Derived points were then converted to the roughness index, Lr |
Sample
semivariance analysis
for Pleurozium schreberi
Max. semivariance = 15.3
Lr = 5.64 mm
|
 |
|
|
|
|