Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1‐km²resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1‐km²pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse‐grained air temperature estimates from ERA5‐Land (an atmospheric reanalysis by the European Centre for Medium‐Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome‐specific offsets emphasize that the projected impacts of climate and climate change on near‐surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil‐related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.

Evaluating soil geochemical diversity in the Amazon Basin has been a challenge largely because most study sites have been at the edge of the basin and it is difficult to get samples in such a region. Here we show that even among the most weathered soils, physicochemical soil properties express lithology. Our results are based on topsoil samples collected from different locations in minimally disturbed areas in the state of Amazonas, Brazil. Soil properties were measured using methods which are suitable for highly developed soils. The Chemical Index Alteration and Weathering Index of Parker was calculated based on the content of metal(loid)s in soils determined by X-ray fluorescence. Descriptive statistics, Pearson correlation, and Principal Component Analysis (PCA) were performed on data. In general, Amazon rainforest soils are more deeply weathered than soils in other Brazilian biomes and tropical rainforests in Asia and Africa. The high coefficient of variation of metal(loid) contents express pedogenesis and parent material diversity. Correlation analysis indicated that the tri-pentavalent elements are strongly associated with Al and Fe contents in the topsoil. In contrast, mono-divalent elements are correlated with sand and silt fractions. According to PCA, five soil groups with defined geochemical compositions and degrees of weathering could be identified: i) acidic sandy podzolized soils; ii) acidic loamy ferralitic soils with the highest content of tri-pentavalent ions; iii) acidic clayey kaolinitic soils with low metal(loid) contents; iv) acidic loamy kaolinitic soils with low metal(loid) contents; and v) silty neutral 2:1 clay soils. This study is the first effort to analyze the geochemical diversity in Amazon rainforest soils. These data are extremely valuable in determining the geochemical background for these soil types and this region. Geochemical variability can be predicted to some extent by lithology and pedogenesis, which can be applied to define the sampling required in future studies.