Light acclimation optimizes leaf functional traits despite height-related constraints in a canopy shading experiment

Within-canopy gradients of leaf functional traits have been linked to both light availability and vertical gradients in leaf water potential. While observational studies can reveal patterns in leaf traits, within-canopy experimental manipulations can provide mechanistic insight to tease apart multip...

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Bibliographic Details
Published in:Oecologia 2015-04, Vol.177 (4), p.1131-1143
Main Authors: Coble, Adam P, Cavaleri, Molly A
Format: Article
Language:English
Subjects:
acclimation
Acclimatization
Acer - growth & development
Acer - metabolism
Acer - physiology
Acer saccharum
Acer saccharum subsp. saccharum
Biomedical and Life Sciences
branches
canopy
carbon
Carbon - metabolism
Carbon Dioxide - metabolism
Carbon Isotopes - metabolism
carbon nitrogen ratio
Darkness
Ecology
forests
growing season
Hydrology/Water Resources
isotopes
leaf water potential
leaves
Life Sciences
Light
microclimate
nitrogen
Nitrogen - metabolism
observational studies
Phenotype
Photosynthesis
PHYSIOLOGICAL ECOLOGY
Physiological ecology - Original research
Plant Leaves - growth & development
Plant Leaves - metabolism
Plant Leaves - physiology
Plant Sciences
shade
stomatal movement
Stress, Physiological
Trees - anatomy & histology
Trees - metabolism
Trees - physiology
vapor pressure
Water - physiology
water use efficiency
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Summary:Within-canopy gradients of leaf functional traits have been linked to both light availability and vertical gradients in leaf water potential. While observational studies can reveal patterns in leaf traits, within-canopy experimental manipulations can provide mechanistic insight to tease apart multiple interacting drivers. Our objectives were to disentangle effects of height and light environment on leaf functional traits by experimentally shading branches along vertical gradients within a sugar maple (Acer saccharum) forest. Shading reduced leaf mass per area (LMA), leaf density, area-based leaf nitrogen (Nₐᵣₑₐ), and carbon:nitrogen (C:N) ratio, and increased mass-based leaf nitrogen (Nₘₐₛₛ), highlighting the importance of light availability on leaf morphology and chemistry. Early in the growing season, midday leaf water potential (Ψₘᵢd), LMA, and Nₐᵣₑₐwere driven primarily by height; later in the growing season, light became the most important driver for LMA and Nₐᵣₑₐ. Carbon isotope composition (δ¹³C) displayed strong, linear correlations with height throughout the growing season, but did not change with shading, implying that height is more influential than light on water use efficiency and stomatal behavior. LMA, leaf density, Nₘₐₛₛ, C:N ratio, and δ¹³C all changed seasonally, suggesting that leaf ageing effects on leaf functional traits are equally as important as microclimatic conditions. Overall, our results indicate that: (1) stomatal sensitivity to vapor pressure deficit or Ψₘᵢdconstrains the supply of CO₂to leaves at higher heights, independent of light environment, and (2) LMA and Nₐᵣₑₐdistributions become functionally optimized through morphological acclimation to light with increasing leaf age despite height-related constraints.
ISSN:0029-8549
1432-1939
DOI:10.1007/s00442-015-3219-4