Improving remote estimation of winter crops gross ecosystem production by inclusion of leaf area index in a spectral model

Radosław Juszczak; Bogna Uździcka; Marcin Stróżecki; Karolina Sakowska

doi:10.7717/peerj.5613

Improving remote estimation of winter crops gross ecosystem production by inclusion of leaf area index in a spectral model

PeerJ. 2018 Sep 21:6:e5613. doi: 10.7717/peerj.5613. eCollection 2018.

Authors

Radosław Juszczak¹, Bogna Uździcka¹, Marcin Stróżecki¹, Karolina Sakowska²

Affiliations

¹ Meteorology Department, Poznan University of Life Sciences, Poznań, Poland.
² Institute of Ecology, University of Innsbruck, Innsbruck, Austria.

Abstract

The hysteresis of the seasonal relationships between vegetation indices (VIs) and gross ecosystem production (GEP) results in differences between these relationships during vegetative and reproductive phases of plant development cycle and may limit their applicability for estimation of croplands productivity over the entire season. To mitigate this problem and to increase the accuracy of remote sensing-based models for GEP estimation we developed a simple empirical model where greenness-related VIs are multiplied by the leaf area index (LAI). The product of this multiplication has the same seasonality as GEP, and specifically for vegetative periods of winter crops, it allowed the accuracy of GEP estimations to increase and resulted in a significant reduction of the hysteresis of VIs vs. GEP. Our objective was to test the multiyear relationships between VIs and daily GEP in order to develop more general models maintaining reliable performance when applied to years characterized by different climatic conditions. The general model parametrized with NDVI and LAI product allowed to estimate daily GEP of winter and spring crops with an error smaller than 14%, and the rate of GEP over- (for spring barley) or underestimation (for winter crops and potato) was smaller than 25%. The proposed approach may increase the accuracy of crop productivity estimation when greenness VIs are saturating early in the growing season.

Keywords: Carbon dioxide fluxes; Croplands; Gross Ecosystem Production; LAI; NDVI; SAVI; Spectral vegetation indices; WDRVI.

Grants and funding

The measurements were funded by the Polish Ministry of Science under project No. 752/1/N-COST-2 010-0 “Assessment of the temporal and spatial variation of the biophysical and spectral indices (NDVI, PRI, WBI) in reference to net exchange of CO₂, CH₄, H₂O between different ecosystems (peatland, forest and arable) and the atmosphere”. During data processing and manuscript writing, Radosław Juszczak was supported by project No. 2016/21/B/ST10/02271 funded by the National Science Centre of Poland. This project has received funding also from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 749323. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.