Water, Energy, and Carbon Cycling in the Sevilleta

1
Water, Energy, and Carbon Cycling in the
Sevilleta

• Shirley Kurc
• PhD candidate, University of Colorado
• Advisor Eric Small

2
Acknowledgements
A Science and Technology Center (STC) of the
National Science Foundation (NSF)
Assistance with field work related to this study
John Boulanger, Jim Elliott, Doug McGhee
3
Outline

• Field Sites
• Methods
• Water and Energy Dynamics (ET)
• Carbon dynamics
• Questions, Future Work

4
Field Sites

• Flat
• Uniform
• Expansive

• Eddy

• Eddy
• Bowen

• Eddy
• Bowen

5
Methods Measuring Evapotranspiration (ET)

• Bowen Ratio Method
• Measure
• Temperature gradient
• Vapor pressure gradient
• Net Radiation
• Ground heat flux
• Calculate ET from energy balance

6
Methods Measuring Evapotranspiration (ET)
7
Why study ET?
Runoff, Infiltration, And Recharge http//jan.ucc
.nau.edu/wittke GLG100/Groundwater.html
Biogeochemical Cycling Photo J. Hendrick
Soil Moisture Dynamics
Land-Atmosphere Interactions http//www.sevilleta.
unm.edu
Riparian Hydrology http//www.sahra.ari
zona.edu
Carbon Cycle http//www.gsfc.nasa.gov/gsfc/
earth/environ/carbon/carbon.htm
8
Water and EnergyWater Balance
9
Water and Energy Energy Balance
rl et
Rn - G SH LE
10
Two Different EcosystemsSite Differences
11
Water and EnergyET is nearly identical at the
sites
12
Water and EnergyAvailable energy is higher at
the grassland
Available Energy (Q) Q Rn G Equals the
sum of latent and sensible heating
13
Water and EnergySoil moisture controls
evaporative fraction
Evaporative Fraction EF LE / Rn G

• The fraction of available energy used toward
  latent heating (et).

r2 0.89
r2 0.82
Shrubland
Grassland
(0-5 cm)
(0-5 cm)
14
Water and EnergyTimescales are Fast
GRASSLAND
SHRUBLAND
Volumetric Water Content
2.9 days
2.3 days
ET
2.3 days
1.4 days
15
Why study Carbon?

• Hydrologic processes mediated by plants
• transpiration
• interception loss
• infiltration
• surface runoff
• Biologic processes mediated by water availability
  in soil
• growth
• reproduction
• seedling establishment
• Woody encroachments identified as possible
  location for carbon sequestration

16
Carbon
17
Carbon
18
Carbon
Grassland
Shrubland
19
Questions, Future Work

• Estimating ET
• ? can we estimate ET from knowledge of soil
  moisture (in the top 5 cm of soil)?
• Partitioning ET into evaporation vs
  transpiration
• how do shrub and grass differ?
• how does the Sevilleta differ from other areas?

20
Questions, Future Work

• Estimating NEE
• can we estimate soil respiration from soil
  moisture?
• are assimilation and respiration dynamics in the
  Sevilleta similar to those in other arid areas?
• Carbon Sequestration
• is this woody encroachment a carbon sink?
• or can we tell?