Conserving rare plants is important to biodiversity. Shrubby reed-mustard [Schoenocrambe suffrutescens (Rollins) S.L. Welsh and Chatterly] (SRM), a shrub endemic to the Uinta Basin, faces habitat loss due to energy development of fossil fuels. Little is known about the soil and site properties required for successful establishment, growth, and survival of SRM. Our goal was to create random forests models to identify potential SRM habitat and to verify habitat suitability in the field with easily measured properties. The soil properties (SP) model indicated that CaCO 3 equivalent, silt, and dry color value predicted the presence or absence of SRM with 10% out-of-bag (OOB) error. Soil properties were correlated with Landsat 5 Thematic Mapper spectral data and a digital elevation model in a Soil-Spectral Correlation (SSC) model. Yellowness, 3/2 normalized difference ratio (NDR), and 3/1 NDR were most strongly correlated with CaCO 3 equivalent and silt, and they predicted SRM habitat with 28% OOB error. guided by SSC model output, 250 additional field presence or absence points were used to train the Spectral-Topographic (ST) model, which was validated by an independent set of SRM plant locations. The ST model using area solar radiation, 7/2 NDR, 5/2 NDR, and the normalized difference vegetation index gave an OOB error of 23%. The ST model can be used to identify potential habitat across a large area. Once identified, easily measured soil and site data from the SP model can verify SRM habitat suitability. These models can help land managers locate and check key soil properties at potential SRM habitat sites.Abbreviations: BLM, Bureau of Land Management; DEM, digital elevation model; NDR, normalized difference ratio; NDVI, normalized difference vegetation index; OOB, outof-bag; SP, soil properties; SRM, shrubby reed-mustard; SSC, soil-spectral correlation; ST, spectral-topographic. P reserving populations of rare plants is important to maintain biodiversity, which increases genetic diversity, provides possible sources of food and medicinal plants, and provides ecosystem services such as protection of soil and water resources, nutrient cycling, and pollutant adsorption or uptake (Australian Department of the Environment, 1993). A species may be rare for a variety of reasons, including low tolerance to environmental change, preference for a very specific habitat, limited dispersal capabilities, etc. Endemic plants are often characterized by few populations concentrated in a narrow geographic distribution. Soil and geologic properties have been successfully used to explain the distribution of some rare endemic plants. For example, endemic species grow in soils formed on serpentinite with low Ca/Mg ratios and high levels of heavy metals (Cr, Co, Ni) inherited from the ultramafic parent material (Alexander et al., 2007;Lazarus et al., 2011;Proctor, 1971;van der Ent and Reeves, 2015
Core Ideasâą Soil and site properties predict rare plant distribution.âą Rare plant habitat can be predicted by random forests modeling of data...