Evidence of Arithmetical Uncertainty in Estimation of Light and Water Use Efficiency

Abstract

It was demonstrated that conventional resource use efficiency (RUE) estimation methodology is largely subject to arithmetic weakness. Extensive field research data on aboveground biomass (AGB), absorbed photosynthetically active radiation (APAR), and crop evapotranspiration (ETc) in maize, soybean, sorghum, and winter wheat confirmed this methodological bias for light use efficiency (LUE) and water use efficiency (WUE) estimation. LUE and WUE were derived using cumulated (data aggregates across samplings) and independent (data increments across samplings) approaches. Use of cumulated data yielded strong-but-false correlation between AGB and APAR or ETc, being a statistical artefact. RUE values from an independent approach were substantially lower than that from a cumulated approach with greater standard errors. Overall, a cumulated approach tends to oversimplify the complex interactions among carbon and resource coupling in agroecosystems, which is accurately represented when employing an independent approach instead.