Hydrostatic constraints on morphological exploitation of light in tall Sequoia sempervirens trees

Hiroaki T. Ishii, Gregory M. Jennings, Stephen C. Sillett, George W. Koch

Research output: Contribution to journalArticle

64 Scopus citations

Abstract

We studied changes in morphological and physiological characteristics of leaves and shoots along a height gradient in Sequoia sempervirens, the tallest tree species on Earth, to investigate whether morphological and physiological acclimation to the vertical light gradient was constrained by hydrostatic limitation in the upper crown. Bulk leaf water potential (Ψ) decreased linearly and light availability increased exponentially with increasing height in the crown. During the wet season, Ψ was lower in the outer than inner crown. C isotope composition of leaves (δ13C) increased with increasing height indicating greater photosynthetic water use efficiency in the upper crown. Leaf and shoot morphology changed continuously with height. In contrast, their relationships with light availability were discontinuous: morphological characteristics did not correspond to increasing light availability above 55-85 m. Mass-based chlorophyll concentration (chl) decreased with increasing height and increasing light availability. In contrast, area-based chl remained constant or increased with increasing height. Mass-based maximum rate of net photosynthesis (P max) decreased with increasing height, whereas area-based P max reached maximum at 78.4 m and decreased with increasing height thereafter. Mass-based P max increased with increasing shoot mass per area (SMA), whereas area-based P max was not correlated with SMA in the upper crown. Our results suggest that hydrostatic limitation of morphological development constrains exploitation of light in the upper crown and contributes to reduced photosynthetic rates and, ultimately, reduced height growth at the tops of tall S. sempervirens trees.

Original languageEnglish (US)
Pages (from-to)751-763
Number of pages13
JournalOecologia
Volume156
Issue number4
DOIs
StatePublished - Jul 1 2008

Keywords

  • Hydrostatic limitation
  • Light interception
  • Maximum tree height
  • Morphological plasticity
  • Water use efficiency

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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