Fig. 1: Global distribution of soil pyrogenic carbon (PyC) measurements.

A The spatial distribution of soil PyC measurements overlaid on the global mean annual burned area. Soil PyC data were extracted from the literature (see Methods). The global mean annual burned area is represented as a percentage of the burnable land area per year (% year⁻¹) in each 0.25° × 0.25° grid cell from 2001 to 2020. Data were from the Global Fire Emission Database (GFED5)¹². The base map is modified from Natural Earth. B The biome distribution of study locations based on mean annual temperature (°C) and mean annual rainfall (cm), following the Whittaker biome classification. C Boxplot of percentage of PyC in soil organic carbon (SOC) (%) according to different methodological approaches. The box represents the interquartile range from the 25^th to the 75^th percentile of the data, with the line inside the box indicating the median value. Whiskers extend to the highest and lowest values within 1.5 times the interquartile range. The dotted line within the box indicates the mean value, and the dashed line indicates the mean value (mean = 11.44, n = 3456) of the whole dataset. The methodological approaches used for PyC determination include benzenepolycarboxylic acid (BPCA) (n = 815), chemothermal oxidation (n = 637), dichromate oxidation (n = 593), nuclear magnetic resonance (NMR) spectroscopy (n = 585), peroxide/weak nitric acid (n = 414), and other (n = 502) (see “Methods”). Source data are provided as a Source Data file.