Global terrestrial plant nitrogen stable isotope ratio samples: 30m centroid of each 0.1 degree grid cell from 1984 to 2022

Annual global maps of foliar δ15N during 1984-2022, produced based on the method described in detail in Yang et al. (in review) . The maps could inform the improvement of nitrogen cycle models and the assessments of the impacts of environmental changes. \n\nThe annual maps are accompanied by the standard deviation of the predictions of the 500 trees of the random forest model. There are addition analysis using Monte Carlo method to quantify the prediction uncertainty in the PredictionUncertainty folder. \n\nLineage: The method to derive the data is described in detail in Yang et al. (in review), with code provided in Yang et al (2024). \n\nBriefly, the Landsat spectra were linked to ground based δ15N data with a random forest model. \n\nWe used surface reflectance from all six spectral bands of Landsat 5 and 8 from 1984-2022. Landsat data in croplands, urban areas, permanent water, ice, or bare ground were removed. \n\nEach ground-based δ15N was matched to a peak-growing season Landsat retrieval with highest green vegetation cover. A random forest model was then fitted to the ground-based δ15N and Landsat spectra. We used multiple validation methods to avoid overfitting and autocorrelation. The maps are generated using the random forest model and the Landsat spectra of the 30m centroid of each 0.1 degree pixel globally. The full description of the method and the evaluation can be found in Yang et al. (in review). In future this collection may be updated with finer resolution data layers.\n\nFILE DESCRIPTION\nThe d15N_01 folder contains the maps of predicted d15N of the 30m centroid of each 0.1 degree grid cell. The SD folder contains the standard deviation of the predictions of all 500 trees of the random forest model. \n\nREFERENCES\nYang et al. (in review) Mapping the multidecadal trends of terrestrial plant nitrogen stable isotope ratios globally. \nYang et al. (2024) A framework to estimate nitrogen stable isotope ratio from satellite spectra. https://data.csiro.au/collection/csiro:62621\n\n