Using automated machine learning for the upscaling of gross primary productivity

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Estimating gross primary productivity (GPP) over space and time is fundamental for understanding the response of the terrestrial biosphere to climate change. Eddy covariance flux towers provide in situ estimates of GPP at the ecosystem scale, but their sparse geographical distribution limits larger-scale inference. Machine learning (ML) techniques have been used to address this problem by extrapolating local GPP measurements over space using satellite remote sensing data. However, the accuracy of the regression model can be affected by uncertainties introduced by model selection, parameterization, and choice of explanatory features, among others. Recent advances in automated ML (AutoML) provide a novel automated way to select and synthesize different ML models. In this work, we explore the potential of AutoML by training three major AutoML frameworks on eddy covariance measurements of GPP at 243 globally distributed sites. We compared their ability to predict GPP and its spatial and temporal variability based on different sets of remote sensing explanatory variables. Explanatory variables from only Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data and photosynthetically active radiation explained over 70 % of the monthly variability in GPP, while satellite-derived proxies for canopy structure, photosynthetic activity, environmental stressors, and meteorological variables from reanalysis (ERA5-Land) further improved the frameworks’ predictive ability. We found that the AutoML framework Auto-sklearn consistently outperformed other AutoML frameworks as well as a classical random forest regressor in predicting GPP but with small performance differences, reaching an r2 of up to 0.75. We deployed the best-performing framework to generate global wall-to-wall maps highlighting GPP patterns in good agreement with satellite-derived reference data. This research benchmarks the application of AutoML in GPP estimation and assesses its potential and limitations in quantifying global photosynthetic activity.

OriginalsprogEngelsk
TidsskriftBiogeosciences
Vol/bind21
Udgave nummer10
Sider (fra-til)2447-2472
ISSN1726-4170
DOI
StatusUdgivet - 2024

Bibliografisk note

Funding Information:
We would like to express our gratitude to Martha Anderson and Christopher Hain for providing the ALEXI ET dataset, which has greatly enriched our research. Furthermore, we are grateful for the provision of the ERA-5 Land dataset, which was generated using Copernicus Climate Change Service information 2019, and for the AMERIFLUX data portal, which is funded by the U.S. Department of Energy Office of Science. We would also like to thank Jiangong Liu and the anonymous reviewers for their helpful contributions.

Funding Information:
This research has been supported by the Department of Energy, Labor and Economic Growth (grant no. DE-SC0021023) and the National Aeronautics and Space Administration (grant nos. 80NSSC21K1705 and 80NSSC20K1801).

Publisher Copyright:
© Author(s) 2024.

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