deforest 11
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Month Day Topic C,M&M
Jan. 6 Introduction8 History of EE 1
10 Earths climate system 2
13 Energy balance 4
15 Water balance 4
17 Climate/vegetation 4
20 HOLIDAY!
22 Soils I 3
24 Soils II 3
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Bowen ratio
Can range from 10 (desert)
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Outline
Water outputs
Measurements
Vegetation and climate
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Transpiration drives water
movement through plant
Water moves in continuous column from
film on soil particles to leaf cells
Moves upward because of strong
cohesive forces among water molecules
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Plants have some water storage capacityQuite limited in most plants (2 hours in this graph)
Most of water must come from soil (not plant storage)
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Water loss from leaves Driving force is vapor pressure gradient
Depends on temperature and water vapor
in bulk air
Stomata are major resistance
Stomatal conductance depends on Soil moisture
Vapor pressure of air (in some species)
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Rate of water loss from leaves
depends on water supply
Influences water potential gradient
Plants adjust stomatal conductance to
match water supply
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Water inputs to ecosystem
determines water outputs
P + S = ET + R
P = Precipitation
S = Storage
ET = Evapotranspiration
R = Runoff
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Controls over ET
Interception
Boundary layer conductance
Physicalcontrol over water loss Depends on vegetation structure and wind
THE majorvegetationcontrolwhensoilsaremoist
Surface conductance
Depends on stomatal conductance
Becomes increasingly important as soils dry
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Streamflow is the leftovers
after storage and ET are met
Over long term, runoff depends on ppt
and ET
Runoff = (P + S) ET
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In moist ecosystems, ET is relatively insensitive to ppt.
Precipitation directly regulates streamflow
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Converting the Amazon to pasture
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Consequences of deforestation 25-40% of ppt in Amazon basin comes from
within-basin ET
Dry air = decreased transport of ocean air tobasin
Permanent reduction in ppt
Favors grasses/savannah vegetation/fire
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Positive feedback to grass/fire
q Rooting depth
q ET/LE
oAirT
o H
q Humidity
q ppt
o Grass/fire
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Forests absorb more radiation (lower albedo)
Forests transfer more sensible heat to atmosphere
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Air over forest is warmer and more humid at any give height
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Positive feedback to migration of treeline
o Trees
o H
qAlbedo
(earlier spring)
o Rnet
oAirT
Warmer climate
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Energy
Measurements Rnet
Storage
Ground heat flux
Sensible heat flux
Latent heat flux
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