Global maps of soil temperature.

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-km <sup>2</sup> resolution 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-km <sup>2</sup> pixels (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

Soil Organic Carbon and Carbon Dioxide Emission from an Organically Amended Hawaiian Tropical Soil

Application of organic manure (OM) to arable lands improves soil tilth. The objectives of this study were to: (i) simulate the effect of OM application rates (0, 168, 336, and 672 kg total N ha -1) and types (chicken [Gallus domesticus] and dairy manures) on soil organic C (SOC) and CO 2 emissions from a Hawaiian highly weathered tropical soil; and (ii) correlate SOC, CO 2 emissions, and two major soil properties: bulk density (ρ b) and saturated hydraulic conductivity (K sat). Measurements of SOC and ρ b were conducted on samples collected from the top 10 cm of soil tilled before and after manure application, cultivated with sweet corn (\u27Super Sweet 10,\u27 Zea mays L. ssp. mays), and drip irrigated for two consecutive growing seasons. The K sat values were calculated from infiltration data measured with a tension infiltrometer. The Rothamsted C turnover model was used to simulate SOC and CO 2 emissions. The simulated and measured SOC agreed reasonably during model calibration (r 2 = 0.93) and validation (r 2 = 0.90). Results revealed that SOC, CO 2 emissions, and K sat increased while ρ b decreased with increasing OM rates. There was no significant effect of OM type. There was a highly significant (P \u3c 0.01) correlation between the measured and simulated SOC and between the measured SOC and the simulated CO 2 emissions. The K sat values significantly correlated (P \u3c 0.05) with the measured and simulated SOC and the simulated CO 2 emissions. A significant inverse relationship between ρ b and K sat was observed. We concluded that, in addition to improving soil aggregation, decreasing ρ b, and increasing K sat;, OM application to this tropical soil increases SOC pools that contribute to atmospheric CO 2 following tillage and other agricultural practices. © Soil Science Society of America