UNC-Chapel Hill GEOG 595 - Lab 5 Compare Stomatal Conductance Models in Modeling Transpiration (3 pages)

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Lab 5 Compare Stomatal Conductance Models in Modeling Transpiration



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Lab 5 Compare Stomatal Conductance Models in Modeling Transpiration

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Pages:
3
School:
University of North Carolina at Chapel Hill
Course:
Geog 595 - Ecological Modeling

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Geog 595 Ecological Modeling Spring 2010 Due March 17 2010 Lab 5 Compare Stomatal Conductance Models in Modeling Transpiration 1 Objectives 1 Understanding three stomatal conductance models in modeling transpiration Jarvis 1976 Ball Berry 1987 and Lenuing 1995 2 Implement the models in C programs 2 Theory Water is an essential resource for plants No plant physiological process can happen without water Plants lose water during the photosynthesis process when stomas open to absorb CO2 in the atmosphere Plants lose more water when the stomas are more open Physiologists use stomatal conductance gsw to describe the openness of stomas It is essential for modelers to numerically describe how stomatal conductance change in difference environmental conditions as it controls the rate of transpiration as well as the rate of photosynthesis Jarvis 1976 provided an empirical model that describe stomatal conductance as in the following g sw g s max f T f PAR f VPD f l f C a 1 where gsmax is the maximum stomatal conductance for the leaves under study i e stomatal conductance with no environmental constrains and the f are scalar functions that evaluate between 0 and 1 for temperature T photosynthetically active radiation PAR vapor pressure deficit VPD leaf water potential l and CO2 concentration in the atmosphere Ca A common maximum conductance value used in the literature is 0 006m s Since the Jarvis model was published there are numerous variation of f which have been used in the literature We will use more recent and simpler scalar functions in this lab f T b3 T Tmin Tmax T b4 2 b4 Tmax Topt Tmax Tmin b3 Topt 1 Tmin Tmax Topt b4 where Tmin Topt and Tmax are minimum optimal and maximum temperature for stomatal opening respectively For most vegetations Tmin 5 0 Topt 25 0 and Tmax 40 0 degrees Celsius A simpler scalar function for PAR will be used as f PAR PAR PPFD50 PAR 3 where PPFD50 is the PAR intensity at half stomotal closure PPFD50 75 mol m 2 s The scalar function for vapor



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