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- Title
Contribution of competition for light to within-species variability in stomatal conductance.
- Authors
Loranty, Michael M.; Mackay, D. Scott; Ewers, Brent E.; Traver, Elizabeth; Kruger, Eric L.
- Abstract
Sap flux ( J S) measurements were collected across two stands dominated by either trembling aspen or sugar maple in northern Wisconsin. Observed canopy transpiration ( E C- obs) values derived from J S were used to parameterize the Terrestrial Regional Ecosystem Exchange Simulator ecosystem model. Modeled values of stomatal conductance ( G S) were used to determine reference stomatal conductance ( G Sref), a proxy for G S that removes the effects of temporal responses to vapor pressure deficit ( D) on spatial patterns of G S. Values of G Sref were compared to observations of soil moisture, several physiological variables, and a competition index ( C I) derived from a stand inventory, to determine the underlying cause of observed variability. Considerable variability in G Sref between individual trees was found, with values ranging from 20 to 200 mmol m−2 s−1 and 20 to 100 mmol m−2 s−1 at the aspen and maple stands, respectively. Model-derived values of G Sref and a sensitivity to D parameter ( m) showed good agreement with a known empirical relationship for both stands. At both sites, G Sref did not vary with topographic position, as indicated by surface soil moisture. No relationships were observed between G Sref and tree height ( H T), and a weak correlation with sapwood area ( A S) was only significant for aspen. Significant nonlinear inverse relationships between G Sref and C I were observed at both stands. Simulations with uniform reductions in incident photosynthetically active radiation ( Q0) resulted in better agreement between observed and simulated E C. Our results suggest a link between photosynthesis and plant hydraulics whereby individual trees subject to photosynthetic limitation as a result of competitive shading exhibit a dynamic stomatal response resulting in a more conservative strategy for managing hydrologic resources.
- Publication
Water Resources Research, 2010, Vol 46, Issue 5, pn/a
- ISSN
0043-1397
- Publication type
Article
- DOI
10.1029/2009WR008125