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Harvard Forest Symposium Abstract 2011

• Title: Seasonal patterns of foliar reflectance in relation to leaf nitrogen and photosynthetic properties in two tree species with a contrasting growth habit, Quercus rubra and Betula papyrifera
• Primary Author: Sophie Dillen (University of Antwerp)
• Additional Authors: Nathan Phillips (Boston University)
• Abstract:

  Seasonal patterns of foliar reflectance in relation to leaf nitrogen and photosynthetic properties in two tree species with a contrasting growth habit, Quercus rubra and Betula papyrifera
  
  
  
  S.Y. Dillen, M. Buonanduci and N.G. Phillips
  
  
  
  Spectral reflectance measurements can provide insights into the physiological performance of leaves. Recent studies suggest a possible link between leaf photosynthetic potential and certain reflectance indices. The occurrence of such a link could be of great value for remote sensing and modeling of vegetation carbon fluxes. We studied seasonal patterns in foliar reflectance in relation to leaf nitrogen as well as structural and photosynthetic properties in two tree species with a contrasting growth habit, red oak (Quercus rubra) and paper birch (Betula papyrifera) at Harvard Forest, Petersham, USA. On a monthly basis the maximum rate of carboxylation (Vcmax) and the maximum rate of electron transport (Jmax) were estimated from leaf-level gas exchange measurements in the upper crown.
  
  
  
  Paper birch continuously produced leaves from early May until late June, while the mature red oak individuals typically had one flush of leaves at the start of the growing season. Both bud flush and leaf fall were significantly earlier in paper birch than in red oak, 10 and 14 days earlier respectively. From June onward, when leaves were fully expanded, oak leaves were characterized by higher values of leaf mass per unit area (LMA), nitrogen concentration (Nmass) and content (Narea) and Vcmax compared to birch leaves.
  
  
  
  Seasonal patterns in leaf photosynthesis and morphology were marked by parallel changes in reflectance indices such as the chlorophyll index (CI) and the photochemical reflectance index (PRI). Differences in leaf photosynthesis and morphology between red oak and paper birch were only apparent from leaf spectra during spring and fall. Thus, between-species differences in leaf nitrogen or photosynthesis in the middle of the growing season could not be acquired through leaf spectral properties. If these observations at leaf level are still valid at canopy level, detection of species may be possible through remote sensing at key times of the growing season, i.e. during fast-changing stages of leaf development and senescence.
  
  

• Research Category: Physiological Ecology, Population Dynamics, and Species Interactions