This layer was produced by the Organic Soils Mapping (OSM) project, a project undertaken by DPIPWE Natural Values Conservation Branch between 2019 and 2021. This project received grant funding from the Australian Government through the Australian Heritage Grants Program, funding from 2017 Tasmanian Bushfire Mitigation fund and The Tasmanian Wilderness World Heritage Area fund. This project has used existing (legacy) data from previous Tasmanian land resource assessment studies, spatial data sets, expert desktop inputs, and newly captured site data from the AHG grant project activities. This project has collated these data to produce this and a further 6 spatial layers that show (presence /absence sites) and predict the likely distribution and characteristics of Organic Soils in Tasmania. The project was focused on the Tasmanian Wilderness World Heritage Area (TWWHA), with modelling applied state-wide to assist in organic soil identification elsewhere. The Organic Soil Mapping was undertaken to specifically identify organic soil extent in the TWWHA and to increases the understanding of the organic soil landscapes and characteristics in greater Tasmania. Organic soil areas are recognised globally as ecologically significant. These landscapes support a diverse range of ecosystems. They also provide and control ecosystem services/processes and provide highly valued carbon and water storage functions. These project outputs aim to improve and assist conservation and management of these important soil landscapes. The mapping was performed using a combination of 30m resolution modelling (Digital Soil Mapping (DSM)), expert digitising, with TASVEG, soil mapping and wetlands datasets as masks. A DSM approach was chosen due to the sparse and limited nature of existing and new field data due to the remote and difficult access. DSM involves using soil site data, intersected with a range of spatial environmental predictor datasets (covariates) to develop a series of landscape models, showing the variation in various soil properties between calibration points through interpolation and extrapolation (Kidd et al 2015). A range of OSM characteristics; extent and likelihood, depth, and drainage were combined into a map of classified characetristics.

Position Accuracy: 30m resolution. Attribute Accuracy: Each Raster cell is attributed by multiple soil models to arrive at a likelihood of organic soil rating. The accuracy is therefore limited by the precision of the input models. The result of the validation diagnostics can be made available for each surface on request. The input soil models validated to at least a reasonable level with the standard error within acceptable ranges. Logical Consistency: All raster cell data are labelled with an approximate organic soil likelihood rating. There are no duplicates. Completeness: The spatial layers cover the entire state of Tasmania, excluding Macquarie Island. Additional: Component layers of Digital Soil Mapping components are available upon request. Statement A presence-absence organic soil extent map was developed using a binary calibration set of site data (1 = Organic Soil Presence, 0 = Organic Soil Absence) from the newly collected data, and any legacy data points classed as an Organosol (Australian Soil Classification) or containing an organic or peat surface layer(s). Expert desktop digitising was undertaken identifying sites highly likely to be non-organic, mainly targeting mountainous bare-earth ridge tops in access-constrained areas, Categorical modelling was initially tested using a decision Tree (See5) approach, however, better results were used when modelling the presence-absence data as a continuous (1 to 0) index, where the modelled surface shows values closer to 1 as having a higher likelihood of being organic (i.e. meeting all the environmental conditions that indicate the presence of an organic soil). This approach allows organic soil area to be better classified by expert review, where; 0.9 - 1 High Likelihood of Organic Soil 0.7 - 0.9 Likely Organic Soil 0.5 - 0.7 Potentially Organic Soil 0 - 0.5 Unlikely to be Organic Soil A similar process was used to create maps for depth and drainage and combined into a characteristics map as follows; Code - Type, Likelihood, Drainage, Depth: ------------------------------------------------ 0 - Non-Organic Soil 2110 - Organic Soil, Moderate Likelihood, Wet, Shallow 2120 - Organic Soil, Moderate Likelihood, Wet, Deep 2210 - Organic Soil, Moderate Likelihood, Dry, Shallow 2220 - Organic Soil, Moderate Likelihood, Dry, Deep 3110 - Organic Soil, High Likelihood, Wet, Shallow 3120 - Organic Soil, High Likelihood, Wet, Deep 3210 - Organic Soil, High Likelihood, Dry, Shallow 3220 - Organic Soil, High Likelihood, Dry, Deep 4110 - Organic Soil, Very High Likelihood, Wet, Shallow 4120 - Organic Soil, Very High Likelihood, Wet, Deep 4210 - Organic Soil, Very High Likelihood, Dry, Shallow 4220 - Organic Soil, Very High Likelihood, Dry, Deep 10000 - Rainforest - Organic Soil, High Uncertainty Further reading: Kidd, D., Malone, B., McBratney, A., Minasny, B., Odgers, N., Webb, M., Searle, R., 2014a. A New Digital Soil Resource for Tasmania, Australia, 20th WORLD CONGRESS OF SOIL SCIENCE, pp. 612-613; Kidd, D., Webb, M., Malone, B., Minasny, B., McBratney, A., 2015a. 80-metre Resolution 3D Soil Attribute Maps for Tasmania, Australia. Soil Research; Kidd, D., Webb, M., Malone, B., Minasny, B., McBratney, A., 2015b. Digital soil assessment of agricultural suitability, versatility and capital in Tasmania, Australia. Geoderma Regional 6, 7-21; Kidd, D.B., Malone, B.P., McBratney, A.B., Minasny, B., Webb, M.A., 2014b. Digital mapping of a soil drainage index for irrigated enterprise suitability in Tasmania, Australia. Soil Research 52, 107-119;