Climatic Suitability and Distribution Prediction of Medicago sativa on the Qinghai–Tibet Plateau: An Ensemble Species Distribution Modeling Approach

Abstract

Medicago sativa L. (M. sativa) is a widely cultivated forage species with potential applications in the phytoremediation of heavy metal-contaminated soils. However, its application on the climate-sensitive Qinghai-Tibet Plateau depends on the availability and future dynamics of climatically suitable habitats. Here, we integrated 12 species distribution models into an ensemble framework to identify the dominant environmental constraints on M. sativa suitability and project its potential distribution under current and future climate scenarios. Elevation and annual temperature range (Bio7) were the primary limiting factors, with suitable conditions occurring mainly below ~3,346.7 m and at Bio7 values of 24.5–34.8 °C. Under current conditions, highly suitable habitats covered 11.77 × 10⁴ km² and were concentrated in the eastern and southern Qinghai–Tibet Plateau. Future climate change substantially expanded the total suitable area, with an increase of up to 46.5% under SSP5-8.5 by the 2090s. In contrast, highly suitable habitats expanded more slowly, with their proportion of the total suitable area declining from 20.9% to ~18.3%, indicating that future expansion will be dominated by low- and moderate-suitability habitats. The distribution centroid generally shifted northwestward and toward higher latitudes. These findings reveal the spatial reorganization of climatic suitability for M. sativa under climate change and provide a spatial basis for prioritizing its potential use in ecological restoration on the Qinghai–Tibet Plateau. Importantly, this study assesses climatic suitability rather than phytoremediation effectiveness and therefore provides a screening framework for identifying candidate regions for the restoration of heavy metal-contaminated soils.