Upscaling Gross Primary Production from Leaf to Canopy for Potato Crop (Solanum tuberosum L.)

Abstract

Estimating gross primary production (GPP) is important to understand the land–atmosphere CO2 exchange for major agroecosystems. Eddy covariance (EC) measurements provide accurate and reliable information about GPP, but flux measurements are often not available. Upscaling strategies gain importance as an alternative to the limitations of the use of the EC. Although the potato provides an important agroecosystem for worldwide carbon balance, there are currently no studies on potato GPP upscaling processes. This study reports two GPP scaling-up approaches from the detailed leaf-level characterization of gas exchange of potatoes. Multilayer and big leaf approaches were applied for extrapolating chamber and biometric measurements from leaf to canopy. Measurements of leaf area index and photosynthesis were performed from planting to the end of the canopy life cycle using an LP-80 ceptometer and an IRGA Li-Cor 6800, respectively. The results were compared to concurrent measurements of surface–atmosphere GPP from the EC measurements. Big-leaf models were able to simulate the general trend of GPP during the growth cycle, but they overestimated the GPP during the maximum LAI phase. Multilayer models correctly reproduced the behavior of potato GPP and closely predicted both: the daily magnitude and half-hourly variation in GPP when compared to EC measurements. Upscaling is a reliable alternative, but a good treatment of LAI and the photosynthetic light-response curves are decisive factors to achieve better GPP estimates. The results improved the knowledge of the biophysical control in the carbon fluxes of the potato crop.

A Review of Methods for Data-Driven Irrigation in Modern Agricultural Systems

“…For example, informing irrigation decisions with sap flow and microtensiometer data requires accepting the assumption of generalizable-crop-and -cultivar-based trunk water status thresholds [30]. When using leaf-level gas exchange measurement systems to estimate whole-plant ET, it is assumed that upscaling methods are accurate, even though these methods include empirical relationships between plant morphology and measurements of LAI and light response, which have not been extensively validated [141]. Even simple methods such as using infrared sensors to measure leaf surface temperature rely on the assumption of adequate conditions for measurement; otherwise, measurement error caused by particles in the air like dust or smoke may be ignored [145].…”

“…In one recent study, researchers used portable gas exchange measurements to measure leaf-level photosynthesis and gas exchange rates, then successfully upscaled these estimates to calculate whole-plant fluxes. Though the efforts to understand canopy level fluxes were successful, researchers noted that upscaling was sensitive to the accuracy of the leaf area index and photosynthetic light curve data used in calculations [141]. Many of the applications of this technology aim to improve ET estimates with other technologies that are more easily generalized over areas relevant to commercial agriculture.…”