<p>Soil is a huge carbon (C) reservoir, but where and how much extra C can be stored is unknown. Here, using 5089 observations, we estimated that the uppermost 30&nbsp;cm of Australian soil holds 13&nbsp;Gt (10–18&nbsp;Gt) of mineral-associated organic carbon (MAOC). Using a frontier line analyses, described in Viscarra Rossel et al. (2023), we estimated the maximum amounts of MAOC that Australian soils could store in their current environments, and calculated the MAOC deficit, or C sequestration potential. We propagated the uncertainties from the frontier fitting and mapped the estimates of these values over Australia using machine learning and kriging with external drift (KED). The maps show regions where the soil is more in MAOC deficit and has greater sequestration potential. The modelling shows that the variation over the whole continent is determined mainly by climate, linked to vegetation, and soil mineralogy. We find that the MAOC deficit in Australian soil is 40&nbsp;Gt (25–60&nbsp;Gt). The deficit in the vast rangelands is 20.84&nbsp;Gt (13.97–29.70&nbsp;Gt) and the deficit in cropping soil is 1.63&nbsp;Gt (1.12–2.32&nbsp;Gt). Our findings suggest that the C sequestration potential of Australian soil is limited by climate.

The soil in terrestrial and blue carbon ecosystems (BCE; mangroves, tidal marshes, seagrasses) is a significant carbon (C) sink. National assessments of C inventories are needed to protect them and aid nature-based strategies to sequester atmospheric carbon dioxide. We harmonised measurements from Australia's terrestrial and BCE and, using consistent multi-scale spatial machine learning, unravelled the drivers of soil organic carbon (SOC) variation and digitally mapped their stocks. The modelling shows that climate and vegetation are continentally the primary drivers of SOC variation. But the underlying regional drivers are ecosystem type, terrain, clay content, mineralogy, and nutrients. The digital soil maps indicate that in the 0-30&nbsp;cm soil layer, terrestrial ecosystems hold 27.6&nbsp;Gt (19.6-39.0&nbsp;Gt), and BCE 0.35&nbsp;Gt (0.20-0.62&nbsp;Gt). Tall open eucalypt and mangrove forests have the largest mean SOC per unit area. Eucalypt woodlands and hummock grassland, which occupy vast areas, store the largest total SOC stock. These ecosystems constitute important regions for conservation, emissions avoidance, and preservation because they also provide additional co-benefits.

This is Version 2 of the Australian soil pH (CaCl₂) product of the Soil and Landscape Grid of Australia.<br><br> It supersedes the Release 1 product that can be found at https://doi.org/10.4225/08/546F17EC6AB6E<br><br> The map gives a modelled estimate of the spatial distribution of the pH of soils across Australia.<br><br> The Soil and Landscape Grid of Australia has produced a range of digital soil attribute products. Each product contains six digital soil attribute maps, and their upper and lower confidence limits, representing the soil attribute at six depths: 0-5&nbsp;cm, 5-15&nbsp;cm, 15-30&nbsp;cm, 30-60&nbsp;cm, 60-100&nbsp;cm and 100-200&nbsp;cm. These depths are consistent with the specifications of the GlobalSoilMap.net project. The digital soil attribute maps are in raster format at a resolution of 3 arc sec (~90 x 90&nbsp;m pixels). An additional measure of model reliability is through assessment of model extrapolation risk. This measure provides users a spatial depiction where model estimates are made within the domain of the observed data or not.<br><br> Detailed information about the Soil and Landscape Grid of Australia can be found at - <a href="https://esoil.io/TERNLandscapes/Public/Pages/SLGA/index.html">SLGA</a><br><br> - Total number of gridded maps for this attribute: 24.<br> - Number of pixels with coverage per layer: 2007M (49200 * 40800).

This is Version 1 of the Australian Soil Effective Cation Exchange Capacity product of the Soil and Landscape Grid of Australia.<br><br> The Soil and Landscape Grid of Australia has produced a range of digital soil attribute products. Each product contains six digital soil attribute maps, and their upper and lower confidence limits, representing the soil attribute at six depths: 0-5&nbsp;cm, 5-15&nbsp;cm, 15-30&nbsp;cm, 30-60&nbsp;cm, 60-100&nbsp;cm and 100-200&nbsp;cm. These depths are consistent with the specifications of the GlobalSoilMap.net project (https://esoil.io/TERNLandscapes/Public/Pages/SLGA/Resources/GlobalSoilMap_specifications_december_2015_2.pdf). The digital soil attribute maps are in raster format at a resolution of 3 arc sec (~90 x 90&nbsp;m pixels).<br><br> These maps are generated by combining the best available Digital Soil Mapping (DSM) products available across Australia.<br><br> <ul style="list-style-type: disc;"><li>Attribute Definition: Cations extracted using barium chloride (BaCl2) plus exchangeable H + Al;</li> <li>Units: meq/100g;</li> <li>Period (temporal coverage; approximately): 1950-2013;</li> <li>Spatial resolution: 3 arc seconds (approx 90&nbsp;m);</li> <li>Total number of gridded maps for this attribute: 18;</li> <li>Number of pixels with coverage per layer: 2007M (49200 * 40800);</li> <li>Data license : Creative Commons Attribution 4.0 (CC BY);</li> <li>Target data standard: GlobalSoilMap specifications;</li> <li>Format: Cloud Optimised GeoTIFF;</li></ul>

Soil collection and analysis of chemical and physical attributes was carried out at the Great Western Woodlands site to provide contextual data for the Biomes of Australian Soil Environments (BASE) soil microbial diversity project.

Soil collection and analysis of chemical and physical attributes was carried out at the Alice Mulga site to provide contextual data for the Biomes of Australian Soil Environments (BASE) soil microbial diversity project.

This dataset consists of bare earth covariates designed to indicate the presence of iron oxides, ferrous minerals, quartz/carbonate and hydroxyl minerals, to support soil and lithological modelling across Australia. <br> Bare earth layers (bands) represent the weighted geometric median of pixel values derived from a 30 year time-series of Landsat 5, 7 and 8 imagery converted to at-surface-reflectance, using the latest techniques to reduce the influence of vegetation (see Publications: Roberts, Wilford & Ghattas 2019). Bare earth layers are (BLUE (0.452 - 0.512), GREEN (0.533 - 0.590), RED, (0.636 - 0.673) NIR (0.851 - 0.879), SWIR1 (1.566 - 1.651) and SWIR2 (2.107 - 2.294) wavelength regions. <br> Covariates are then derived from principal components analysis and ratios of specific bare earth layers to target identification of elements of surface geochemistry. Layers are available as mosaics or tiles in 30 or 90 metre resolution.<br>

Soil collection and analysis of chemical and physical attributes was carried out at the Litchfield Savanna site to provide contextual data for the Biomes of Australian Soil Environments (BASE) soil microbial diversity project.

Soil collection and analysis of chemical and physical attributes was carried out at the Whroo Dry Eucalypt site to provide contextual data for the Biomes of Australian Soil Environments (BASE) soil microbial diversity project.

Soil collection and analysis of chemical and physical attributes was carried out at the Samford Peri-Urban site to provide contextual data for the Biomes of Australian Soil Environments (BASE) soil microbial diversity project.