Determining a robust indirect measurement of leaf area index in California vineyards for validating remote sensing-based retrievals
White, William A.
Alsina, Maria Mar
McKee, Lynn G.
Kustas, William P.
Accurate ground-based measurements of leaf area index (LAI) are needed for validation of remote sensing-based retrievals used in models estimating plant water use, stress, carbon assimilation and other land surface processes. Several methods for indirect LAI estimation with the Plant Canopy Analyzer (PCA, LAI-2200C, LI-COR, Lincoln, NE, USA) were evaluated using destructive (direct) leaf area measurements in three split-canopy vineyards and one double-vertical vineyard in California, as part of the Grape Remote sensing and Atmospheric Profile and Evapotranspiration eXperiment (GRAPEX). A method with the sensor facing the canopy, and four readings occurring evenly across the interrow space, had a coefficient of determination (R2) of 0.87 and relative root mean square error (RRMSE) of 16%, when compared to direct LAI measurements via destructive sampling. A previously used method, with the sensor facing down-row, showed lower correlation to direct LAI (R2 = 0.75, RRMSE = 33%) and underestimation which was mitigated by removing the outer sensor rings from analysis. A PCA method is recommended for rapid and accurate LAI estimation in split-canopy vineyards, though local calibration may be required. The method was tested within small units of ground surface area, which compliments high-resolution datasets such as those acquired by small unmanned aerial vehicles. The utility of ground-based LAI measurements to validate remote sensing products is discussed.
Accepted version (Postprint)
634 - Horticultura. Viticultura
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White, William A., Maria Mar Alsina, Héctor Nieto, Lynn G. McKee, Feng Gao, and William P. Kustas. 2019. "Determining A Robust Indirect Measurement Of Leaf Area Index In California Vineyards For Validating Remote Sensing-Based Retrievals". Irrigation Science 37 (3): 269-280. doi:10.1007/s00271-018-0614-8.
Ús Eficient de l'Aigua en Agricultura
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