Functional significance of variation in bryophyte canopy structure

Citation
Sk. Rice et al., Functional significance of variation in bryophyte canopy structure, AM J BOTANY, 88(9), 2001, pp. 1568-1576
Citations number
43
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Plant Sciences
Journal title
AMERICAN JOURNAL OF BOTANY
ISSN journal
0002-9122 → ACNP
Volume
88
Issue
9
Year of publication
2001
Pages
1568 - 1576
Database
ISI
SICI code
0002-9122(200109)88:9<1568:FSOVIB>2.0.ZU;2-Z
Abstract
In most bryophytes, the thickness of boundary layers (i.e., unstirred layer s) that surrounds plant surfaces governs rates of water loss. Architectural features of canopies that influence boundary layer thickness affect the wa ter balance of bryophytes. Using field samples (9.3 em diameter cushions) f rom 12 populations (11 species) of mosses and liverworts, we evaluated the relationship between canopy structure and boundary layer properties. Canopy structure was characterized using a contact surface probe to measure canop y depth along perpendicular transects at spatial scales ranging from 0.8 to 30 mm on 186 points per sample. Semivariance in depth measurements at diff erent spatial scales was used to estimate three architectural properties: s urface roughness (L-r), the scale of roughness elements (S-r), and fine-sca le surface texture, the latter characterized by the fractal dimension (D) o f the canopy profile. Boundary layer properties were assessed by evaporatio n of ethanol from samples in a wind-tunnel at wind speeds from 0.6 to 4.2 m /s and applied to characterize mass transfer using principles of dynamic si milarity (i.e., using dimensionless representations of conductance and flow ). In addition, particle image velocimetry (PIV) was used to visualize and quantify flow over two species. All cushions exhibited the characteristics of turbulent as opposed to laminar boundary layers, and conductance increas ed with surface roughness. Bryophyte canopies with higher L-r had greater c onductances at all wind speeds. Particle image velocimetry analysis verifie d that roughness elements interacted with flow and caused turbulent eddies to enter canopies, enhancing evaporation. All three morphological features were significantly associated with evaporation. When L-r, S-r, and D were i ncorporated with a flow parameter into a conductance model using multiple l inear regression, the model accounted for 91% of the variation in mass tran sfer.