Ohm’s Law
Current 
Fick’s Law Of Diffusion
Voltage Difference
Resistance
Series
r1
r2
Concentration Difference
Diffusion Resistance
CO2
R=r1+r2

g1=1/r1 g2=1/r2
Flux 
H2O
rbu
G=1/R=g1g2/(g1+g2)
Heat
rbu
rsu
Parallel
g1=1/r1
r1
r2
g2=1/r2
rsl

G=g1+g2
R=1/G=r1r2/(r1+r2)
rbl
CO2
H2O
rbl
Heat
Figure 16.1
Ecological Climatology © 2008 G. Bonan
Boundary Layer
Thickness:
1 to 10 mm
rb
Leaf Cuticle
Sensible Heat
rb
Height
Water Vapor
CO2
Guard
Cell
Guard Cell
High
0
Wind Speed
Photosynthetically
Active Radiation
Chloroplast
Low
High
Temperature
rs
Low
CO2
Moist
Air
light
CO2 + 2 H2O  CH2O + O2 + H2O
Figure 16.2
Ecological Climatology © 2008 G. Bonan
40
28
44
20
32
24
36
16
20
12
8
Figure 16.3
Ecological Climatology © 2008 G. Bonan
Figure 16.4
Ecological Climatology © 2008 G. Bonan
Sunny
Shady
Solar Radiation
Cold
Hot
Temperature
Figure 16.5
Ecological Climatology © 2008 G. Bonan
Sunny
Shady
Solar Radiation
Mesic
Xeric
Moisture
Figure 16.6
Ecological Climatology © 2008 G. Bonan