Growing season variability in evapotranspiration, ecosystem water use efficiency, and energy
partitioning in switchgrass
Highlights
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An ongoing Biomass Research and Development Initiative (BRDI) - USDA funded project
is evaluating Evapotranspiration (ET), ecosystem water use efficiency (EWUE), and
energy partitioning in switchgrass (Panicum virgatum L.) at South Central Research
Station, Chickasha, OK, USA.
Understanding switchgrass water and energy balances is crucial as its acreage is
expanding for cellulosic biofuels.
In 2011, seasonal (May to mid-November) cumulative ET (450 mm) was similar to
cumulative rainfall (432 mm). During June to September, when crop experienced
extreme drought, ET was 1·92 times of rainfall.
Estimation of Ecosystem Water
Use Efficiency (EWUE) by dividing
time integrals of gross ecosystem
photosynthesis (GEP) by
respective H2O fluxes (ET) at
monthly time scale provided
EWUE from 10·46 (August) to
14·08 g CO2 mm−1 ET (October)
with a seasonal average of
12·01 g CO2 mm−1 ET.
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Seasonal patterns in EWUE were observed with smaller values during drought because
of more rapid reduction in carbon assimilation (GEP) than ET.
These findings in the recently published manuscript (citation below) confirm the major
role of precipitation in determining water and energy balances in switchgrass.
Wagle, P. and Kakani, V. G. (2012). Growing season variability in evapotranspiration,
ecosystem water use efficiency, and energy partitioning in switchgrass. Ecohydrol.. doi:
10.1002/eco.1322 (http://onlinelibrary.wiley.com/doi/10.1002/eco.1322/abstract)