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dc.contributor.authorOishi, A. Christopher
dc.contributor.authorOren, Ram
dc.contributor.authorStoy, Paul C.
dc.date.accessioned2019-02-25T15:55:26Z
dc.date.available2019-02-25T15:55:26Z
dc.date.issued2008-10
dc.identifier.citationOishi, A. Christopher, Ram Oren, and Paul C. Stoy. “Estimating Components of Forest Evapotranspiration: A Footprint Approach for Scaling Sap Flux Measurements.” Agricultural and Forest Meteorology 148, no. 11 (October 2008): 1719–1732. doi:10.1016/j.agrformet.2008.06.013.en_US
dc.identifier.issn0168-1923
dc.identifier.urihttps://scholarworks.montana.edu/xmlui/handle/1/15278
dc.description.abstractForest evapotranspiration (ET) estimates that include scaled sap flux measurements often underestimate eddy covariance (EC)-measured latent heat flux (LE). We investigated potential causes for this bias using 4 years of coupled sap flux and LE measurements from a mature oak-hickory forest in North Carolina, USA. We focused on accuracy in sap flux estimates from heat dissipation probes by investigating nocturnal water uptake, radial pattern in flux rates, and sensor-to-stand scaling. We also produced empirical functions describing canopy interception losses (measured as the difference between precipitation and throughfall) and soil evaporation (based on wintertime eddy covariance fluxes minus wintertime water losses through bark), and added these components to the scaled sap flux to estimate stand evapotranspiration (ETS). We show that scaling based on areas in which the leaf area index of predominant species deviates from that of the EC footprint can lead to either higher or lower estimate of ETS than LE (i.e. there is no bias). We found that accounting for nocturnal water uptake increased the estimate of growing season transpiration by an average of 22%, with inter-annual standard deviation of 4%. Annual ETSestimate that included sap flux corrected for nocturnal flux and scaled to the EC footprint were similar to LE estimates (633 ± 26 versus 604 ± 19 mm, respectively). At monthly or shorter time scales, ETS was higher than LE at periods of low flux, similar at periods of moderate flux, and lower at periods of high flux, indicating potential shortcomings of both methods. Nevertheless, this study demonstrates that accounting for the effects of nocturnal flux on the baseline signal was essential for eliminating much of the bias between EC-based and component-based estimates of ET, but the agreement between these estimates is greatly affected by the scaling procedure.en_US
dc.language.isoenen_US
dc.rightsThis Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).en_US
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en_US
dc.titleEstimating Components of Forest Evapotranspiration: A Footprint Approach for Scaling Sap Flux Measurementsen_US
dc.typeArticleen_US
mus.citation.extentfirstpage1719en_US
mus.citation.extentlastpage1732en_US
mus.citation.issue11en_US
mus.citation.journaltitleAgricultural and Forest Meteorologyen_US
mus.citation.volume148en_US
mus.identifier.categoryLife Sciences & Earth Sciencesen_US
mus.identifier.doi10.1016/j.agrformet.2008.06.013en_US
mus.relation.collegeCollege of Agricultureen_US
mus.relation.departmentLand Resources & Environmental Sciences.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.data.thumbpage5en_US


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