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Harvard Forest Symposium Abstract 2011

• Title: Stomatal control of canopy conductance
• Primary Author: Jim Wheeler (Harvard University)
• Additional Authors: Noel Michele Holbrook (Harvard Forest)
• Abstract:

  Many mathematical models attempt to predict the transpiration of forest canopies under specific environmental conditions. Usually these models consider the canopy or individual trees as composite resistors, with a resistance value for the wood (sometimes coupled with a capacitor) and a resistance value for the stomata. The resistance of the wood is fixed under most conditions, and the stomatal resistance typically varies as a linear function of water potential. The limited existing measurements of stomatal conductance verses water potential show that this relationship is frequently non-linear.
  
  This project will investigate the behavior of the stomata of canopy trees in situ. How do stomata respond to daily patterns of sunlight and vapor pressure deficit, how do they respond to water stress, and how variable are these responses across the canopy of individual trees. We will combine leaf level photosynthesis measurements, water potential measurements, sap flow techniques and hydraulic measurements to determine how water is distributed throughout the canopy of individual trees, and what role stomata play in controlling this distribution.
  
  
  
  

• Research Category: Forest-Atmosphere Exchange