Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees

Anthony R. Ambrose, Wendy L. Baxter, Christopher S. Wong, Stephen S O Burgess, Cameron B. Williams, Rikke R. Næsborg, George W Koch, Todd E. Dawson

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Optimality theory states that whole-tree carbon gain is maximized when leaf N and photosynthetic capacity profiles are distributed along vertical light gradients such that the marginal gain of nitrogen investment is identical among leaves. However, observed photosynthetic N gradients in trees do not follow this prediction, and the causes for this apparent discrepancy remain uncertain. Our objective was to evaluate how hydraulic limitations potentially modify crown-level optimization in Sequoiadendron giganteum (giant sequoia) trees up to 90 m tall. Leaf water potential (Ψl) and branch sap flow closely followed diurnal patterns of solar radiation throughout each tree crown. Minimum leaf water potential correlated negatively with height above ground, while leaf mass per area (LMA), shoot mass per area (SMA), leaf nitrogen content (%N), and bulk leaf stable carbon isotope ratios (δ13C) correlated positively with height. We found no significant vertical trends in maximum leaf photosynthesis (A), stomatal conductance (gs), and intrinsic water-use efficiency (A/gs), nor in branch-averaged transpiration (EL), stomatal conductance (GS), and hydraulic conductance (KL). Adjustments in hydraulic architecture appear to partially compensate for increasing hydraulic limitations with height in giant sequoia, allowing them to sustain global maximum summer water use rates exceeding 2000 kg day−1. However, we found that leaf N and photosynthetic capacity do not follow the vertical light gradient, supporting the hypothesis that increasing limitations on water transport capacity with height modify photosynthetic optimization in tall trees.

Original languageEnglish (US)
Pages (from-to)713-730
Number of pages18
JournalOecologia
Volume182
Issue number3
DOIs
StatePublished - Nov 1 2016

Fingerprint

Sequoiadendron giganteum
fluid mechanics
hydraulics
leaves
leaf water potential
tree crown
stomatal conductance
carbon
sap flow
diurnal variation
nitrogen content
water use efficiency
carbon isotope ratio
transpiration
nitrogen
isotopes
solar radiation
leaf area
water
photosynthesis

Keywords

  • Hydraulic conductance
  • Hydraulic limitation
  • Sap flow
  • Sequoiadendron giganteum
  • Tree size
  • Xylem conduit widening

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Cite this

Ambrose, A. R., Baxter, W. L., Wong, C. S., Burgess, S. S. O., Williams, C. B., Næsborg, R. R., ... Dawson, T. E. (2016). Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees. Oecologia, 182(3), 713-730. https://doi.org/10.1007/s00442-016-3705-3

Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees. / Ambrose, Anthony R.; Baxter, Wendy L.; Wong, Christopher S.; Burgess, Stephen S O; Williams, Cameron B.; Næsborg, Rikke R.; Koch, George W; Dawson, Todd E.

In: Oecologia, Vol. 182, No. 3, 01.11.2016, p. 713-730.

Research output: Contribution to journalArticle

Ambrose, AR, Baxter, WL, Wong, CS, Burgess, SSO, Williams, CB, Næsborg, RR, Koch, GW & Dawson, TE 2016, 'Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees', Oecologia, vol. 182, no. 3, pp. 713-730. https://doi.org/10.1007/s00442-016-3705-3
Ambrose AR, Baxter WL, Wong CS, Burgess SSO, Williams CB, Næsborg RR et al. Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees. Oecologia. 2016 Nov 1;182(3):713-730. https://doi.org/10.1007/s00442-016-3705-3
Ambrose, Anthony R. ; Baxter, Wendy L. ; Wong, Christopher S. ; Burgess, Stephen S O ; Williams, Cameron B. ; Næsborg, Rikke R. ; Koch, George W ; Dawson, Todd E. / Hydraulic constraints modify optimal photosynthetic profiles in giant sequoia trees. In: Oecologia. 2016 ; Vol. 182, No. 3. pp. 713-730.
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