Suitable Planting Area Prediction for Two <i>Arnebia</i> Species: An Analysis Based on Habitat and Phytochemical Suitability

The distribution of suitable habitats for medicinal plants is affected by climate, soil, land use, and other factors. <i>Arnebiae Radix</i>, an important traditional Chinese medicinal resource in Xinjiang, includes <i>Arnebia euchroma</i> (Royle) I. M. Johnst. and <i>Arnebia guttata</i> Bunge and is at risk of over-exploitation. This study predicted suitable planting areas by integrating habitat and phytochemical suitability using the MaxEnt model and ArcGIS. The AUC values for <i>A. euchroma</i> and <i>A. guttata</i> were 0.977 and 0.952, with TSS values of 0.829 and 0.725, respectively, validating the high accuracy of the prediction model. Under the current scenario, the areas of suitable habitats for <i>A. euchroma</i> and <i>A. guttata</i> were 108,914 and 176,445 km², mainly distributed along the main mountains in Xinjiang. Under future climate scenarios, the suitable habitat area of <i>A. euchroma</i> increased by 11–18%, except in the ssp126-2090s scenario, while the suitable habitat area of <i>A. guttata</i> area decreased by 3–18%. Both species were influenced by land use/land cover and soil available nitrogen content; additionally, <i>A. euchroma</i> was affected by the precipitation in the driest month, and <i>A. guttata</i> by the mean diurnal range. The content of secondary metabolites was positively correlated with habitat suitability, with soil factors contributing 35.25% to the total secondary metabolite content. Their suitable habitats predominantly occur in grasslands (42–82%). As habitat and phytochemical suitability distributions aligned, the eastern and western sides of the northern Kunlun Mountain Pass emerged as key areas for cultivation. This research can provide a scientific foundation for selecting optimal planting regions for the two <i>Arnebia</i> species.