Do we really need large spectral libraries for the assessment of soil organic carbon at local scale?

  1. César Guerrero Maestre 3
  2. Johanna Wetterlind 2
  3. Bo Stenberg 2
  4. Raphael A. Viscarra Rossel 4
  5. Raúl Zornoza Belmonte 3
  6. Fernando T. Maestre 6
  7. Abdul M. Mouazen 1
  8. Boyan Kuang 1
  9. José Damián Ruiz Sinoga 5
  10. Miguel Ángel Galeote Moreno 5
  1. 1 Cranfield University
    info

    Cranfield University

    Cranfield, Reino Unido

    ROR https://ror.org/05cncd958

  2. 2 Swedish University of Agricultural Sciences (SLU)
  3. 3 Universidad Miguel Hernández de Elche
    info

    Universidad Miguel Hernández de Elche

    Elche, España

    ROR https://ror.org/01azzms13

  4. 4 CSIRO Land and Water, Canberra, Australia
  5. 5 Universidad de Málaga
    info

    Universidad de Málaga

    Málaga, España

    ROR https://ror.org/036b2ww28

  6. 6 Universidad Rey Juan Carlos
    info

    Universidad Rey Juan Carlos

    Madrid, España

    ROR https://ror.org/01v5cv687

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Actes:
European Geosciences Union General Assembly 2014

Any de publicació: 2014

Tipus: Aportació congrés

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Resum

Spiking is an approach to improve the accuracy of large-scale spectroscopic models when they are used to predict at local scale. But, if models are to be spiked, do we really need large-sized spectral libraries? Different calibrations relating the SOC and NIR spectra were obtained using PLS as regression method: i) model #1: local-scale model (n=40); ii) model #2: local-scale model (n=88); iii) model #3: provincial-scale model (n=147); iv) model #4: provincial-scale model, constructed with 50% of samples used in model #3 (n=73); v) model #5: provincial-scalemodel, constructed with 25% of samples used in model #3 (n=36); vi) model #6: national-scale model (n=1096); vii) model #7: national-scale model, constructed with 33% of samples used in model #6 (n=362). Each of these models was used to predict the SOC contents in target site samples. In this work, nine target sites were evaluated. Each target site is a relatively small area (from several hectares to a few square kilometers), where a dense sampling was made. The coefficient of the determination (R2 ), root mean square error of prediction (RMSEP), bias, standard error of prediction (SEP) and the ratio of performance to deviance (RPD) were calculated pooling the predictions of the nine target sites. In overall, more than 900 local samples were predicted. The highest R2 values were obtained with the national-scale models (R2 >0.85), and the lowest R2 values were obtained with the models of small size.In general, the RMSEP tended to decrease with the increase of the models size. However, the predictions obtained with the large-sized models were clearly biased, and despite the high R2 values, the RPD values were below 1.2. We also obtained predictions when these models were spiked with eight local samples (i.e., from the target site)