Inferring transpiration control from sap flow heat gauges and the Penman-Monteith equation

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Show simple item record Aiken, Robert M. Klocke, N. L. 2012-09-04T20:10:01Z 2012-09-04T20:10:01Z 9/4/2012
dc.description.abstract In situ measurements of crop transpiration can enhance field studies of crop water use and productivity. Our objectives were to develop and evaluate a canopy resistance model, to evaluate operational characteristics of sap flow heat gauges (SFHG) for field corn (Zea mays L.), and to compare transpiration flux calculated by SFHG with evapotranspiration (ET) calculated by a Penman-Monteith (P-M) algorithm. Five sap flow heat gauges, controlled by an automated data acquisition system, were deployed in each of four replicated field plots of corn irrigated to limit water deficits to 50% of available water capacity at Garden City, Kansas, in 2004 and 2006. Water flux through each stem was estimated as a residual of a heat balance equation. Gauges were transferred to adjacent plants after 13 to 21 days to evaluate and mitigate functional stem damage. Loss of gauge operation, primarily due to stem damage, commonly occurred approximately one to two weeks following installation. Data screened using operational metrics were used to evaluate a scaling relationship between calculated flow to ET calculated following the P-M form. A canopy resistance model was derived from principles of radiation use. Transpiration calculated from gauge data was linearly related to ET calculated from the P-M, with R[superscript]2 exceeding 0.79. Greater precision was obtained by assuming constant canopy resistance (r[subscript]c), but predictive bias was reduced by assuming that r[subscript]c was proportional to solar radiation. Sap flow gauges provided information useful for calibrating an r[subscript]c model for P-M to calculate the transpiration component of ET; the model linking canopy resistance to absorbed radiation has application to dual-source and thermal-based energy balance models of crop ET. en_US
dc.relation.uri en_US
dc.rights © 2012 American Society of Agricultural and Biological Engineers en_US
dc.subject Canopy resistance en_US
dc.subject Evaporation en_US
dc.subject Penman-Monteith en_US
dc.subject Radiation use en_US
dc.subject Sap flow heat gauges en_US
dc.subject Transpiration en_US
dc.title Inferring transpiration control from sap flow heat gauges and the Penman-Monteith equation en_US
dc.type Article (publisher version) en_US 2012 en_US
dc.citation.epage 549 en_US
dc.citation.issue 2 en_US
dc.citation.jtitle Transactions of the ASABE en_US
dc.citation.spage 543 en_US
dc.citation.volume 55 en_US
dc.contributor.authoreid raiken, nklocke en_US

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