Physiological consequences of height-related morphological variation in Sequoia sempervirens foliage

Abstract

This study examined relationships between foliar morphology and gas exchange characteristics as they vary with height within and among crowns of Sequoia sempervirens D. Don trees ranging from 29 to 113 m in height. Shoot mass:area (SMA) ratio increased with height and was less responsive to changes in light availability as height increased, suggesting a transition from light to water relations as the primary determinant of morphology with increasing height. Mass-based rates of maximum photosynthesis (A(max,m)), standardized photosynthesis (A(std,m)) and internal CO(2) conductance (g(i,m)) decreased with height and SMA, while the light compensation point, light saturation point, and mass and area-based rates of dark respiration (R(m)) increased with height and SMA. Among foliage from different heights, much of the variation in standardized photosynthesis was explained by variation in g(i,) consistent with increasing limitation of photosynthesis by internal conductance in foliage with higher SMA. The syndrome of lower internal and stomatal conductance to CO(2) and higher respiration may contribute to reductions in upper crown growth efficiency with increasing height in S. sempervirens trees.

Relationships Between Tree Height and Carbon Isotope Discrimination

“…Internal conductance has been shown to increase with light or height (Le Roux et al 2001;Warren et al 2003). In two tall species, however, g i and g s declined linearly with increased h (Ambrose et al 2009;Mullin et al 2009;Woodruff et al 2009). Patterns of g i with h must be interpreted cautiously in light of the challenges to accurate measurement associated with g i methodologies (Bickford et al 2009;Pons et al 2009).…”

“…This hypothesis can be tested by thorough accounting of the vertical gradients of the above-mentioned key variables that influence D, both within the canopies of tall trees and across the sunlit tops of trees of different heights (e.g. Mullin et al 2009).…”

“…Measuring within-canopy gradients avoids the assumptions of space-for-time substitution, however, and provides useful information on the combined light/hydraulic impacts on D, as well as information on withintree homeostatic adjustments (Hubbard et al 2002;Ishii et al 2008). Since both approaches are useful, combining them in future studies may reveal more information than studying only tree tops or only within-tree gradients (Mullin et al 2009). Fourth, as noted earlier, comprehensive measurements of environmental and physiological drivers of D with h are needed within studies, including light, humidity, gravitational potential, hydraulic conductance, gas exchange, leaf mass per area, leaf nutrients, woody anatomy, and leaf area:sapwood area ratios.…”

The need for a canopy perspective to understand the importance of phenotypic plasticity for promoting species coexistence and light‐use complementarity in forest ecosystems

“…A marked example is the vertical variation in leaf morphology of S. sempervirens, the world's tallest tree species. (Ishii et al 2008;Koch et al 2004;Mullin et al 2009;Oldham et al 2010). In S. sempervirens, leaf mass per area (LMA) can change as much as 2.5-fold within the crown of a single tree (Fig.…”

How Do Changes in Leaf/Shoot Morphology and Crown Architecture Affect Growth and Physiological Function of Tall Trees?

“…For example, in Scots pine, light intensity increases exponentially with increasing height in the crown, but the rate of change in leaf morphology decreases, resulting in a non-linear relationship between morphology and light intensity (Stenberg et al 2001). Leaf morphology also tends to be different between the top-most leaves of tall and short trees even when both are growing in similar light conditions (Woodruff et al 2008;Ambrose et al 2009;Mullin et al 2009). The leaves of an epiphytic sapling growing atop a 30-m tall Japanese cedar (Cryptomeria japonica) tree tend to be more expanded than the leaves of its mother tree, even though both leaves occur adjacent to each other in the same light environment, suggesting that light is not the only factor influencing leaf morphology in tall trees ( Fig.…”