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ARS Home » Plains Area » El Reno, Oklahoma » Oklahoma and Central Plains Agricultural Research Center » Livestock, Forage and Pasture Management Research Unit » Research » Publications at this Location » Publication #396628
Research Project: Integrated Agroecosystem Research to Enhance Forage and Food Production in the Southern Great Plains

Location: Livestock, Forage and Pasture Management Research Unit

Title: Sensitivity of water use efficiency parameterizations on flux variance similarity-based partitioning of evapotranspiration

Author
item Wagle, Pradeep
item RAGHAV, PUSHPENDRA - University Of Alabama
item KUMAR, MUKESH - University Of Alabama

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Abstract only.

Technical Abstract: Despite the high sensitivity of water use efficiency (WUE) estimates to intracellular carbon dioxide concentrations (ci) in the Flux Variance Similarity (FVS)-based partitioning method, sensitivity analysis of ci parameterizations is lacking. Using high-frequency eddy covariance data for two crop sites: wheat (Triticum aestivum L.) and canola (Brassica napus L.), we performed a sensitivity analysis of four ci parameterizations (constant ppm, constant ratio, and square root and linear functions of vapor pressure deficit) and compared them with the optimized WUE approach with no adjustable parameter. Results illustrated large dependencies of WUE estimates and transpiration (T) to evapotranspiration (ET) ratios with differences in ci parameterizations. Notably, constant_ppm and constant_ratio parametrizations for the fourth or fifth-largest ci (commonly used default values in most previous studies) showed comparable T:ET with the optimized WUE approach. Additionally, these three models produced reduced T:ET in wet periods and increased T:ET in dry periods. In contrast, square root and linear models were unable to accurately capture expected trends of T:ET for wet and dry periods, and also showed large discrepancies when compared with the optimal WUE approach. The results highlight that optimal parameterizations of ci should be derived in constant_ppm and constant_ratio methods to accurately capture temporal variations of WUE and T:ET. The results also indicated the potential of the optimum model for inter-model comparison, especially in sensitivity analysis, for FVS partitioning in C3 species. The study demonstrates the sensitivity of FVS partitioning to varying ci parameterizations in different WUE algorithms and underscores the need to reduce uncertainty for more accurate partitioning.