Download Geog595 Ecological Modeling

Geog595 Ecological Modeling
Spring 2010
Due: March 24, 2010
Lab 6 Integrative Modeling of Energy, Water and Carbon Fluxes of Terrestrial
Ecosystems
1. Objectives
(1) Understanding how energy, water and carbon fluxes are simulated
simultaneous in a computer model.
(2) Learn to write a multiple-component computer model in C
2. Theory
The core physical and ecological processes of energy interception by vegetation canopies,
control of water fluxes by stomata, and carbon assimilation have been the major topic of
the course so far. This lab integrates the various components that we modeled in previous
labs into a single model. The integrated model takes the driving variables, including soils
moisture, soil temperature, wind speed, precipitation, PAR, air temperature, and vapor
pressure deficit. Radiation interception, stomatal conductance and transpiration have been
described in labs 1 to 5. We added plant photosynthesis in this lab. We used Farquhar’s
photosynthesis model coupled with Ball-Woodward-Berry stomatal conductance model
and the Fick’s law as in the following:
A  gsc (C a  Ci )
Ah
g sc  g 0  g1
Ca
A  min( A v , A J )
Where Ci and Ca are the CO2 concentration in the intercellular space and the atmosphere
respectively. The relative humidity is h, and g0 is cuticular conductance (0.01 mol/m2/s)
and g1 is the slope parameter. Av and Aj are the carboxylation-limited photosynthesis rate
and RuBP regeneration-limited photosynthesis rate. Among these three equations, there
are three unknowns: A, Ci, and gsc. Thus they can be solved from these three equations.
The carboxylation-limited net photosynthesis rate is,
Av 
Vcmax (Ci  Γ * )
 Rd
Ci  K C (1  O/K O )
(E1)
and RuBP regeneration-limited net photosynthesis rate is
J (Ci   * )
Aj 
 Rd ,
4.5Ci  10.5 *
(E2)
The CO2 concentrations in the atmosphere, at the leaf surface, and in the leaf intercellular
space are Ca, Cs and Ci, respectively. Ci is the leaf space CO2 concentration, and O is the
leaf space oxygen concentration. Vcmax is the maximum rate of carboxylation, which
depends on leaf nitrogen content. Nitrogen content in the canopy is assumed decrease
exponentially with depth. J is the electron transport rate and Rd is day respiration of the
leaves.
3. Numerical Experiment
(1) Based on the main.c program and the functions used in the program, draw
a flow diagram to show how net radiation, transpiration and
photosynthesis are modeled.
(2) Run the model for 2001 and compare the simulated net radiation,
evapotranspiration and net photosynthesis with the tower observations for
2001 with three scatter plots (include in the lab report). Describe how well
they compare with the observations in the file PSN-ET-RnetMay2001Daytime.txt. The last three columns of the data are net photosynthesis, ET
and net radiation, respectively. Please also view the three modeled
quantities in time series plots with the measured and modeled data in the
same graph (not to include in the lab report). Describe how these
quantities compare with the measurements.
(3) Compare the results of ET modeled here with that obtained from lab 4 and
see how well the results from the integrative model. How would you
explain the difference in the comparison with the observed data by the two
models?