Abstract: Aims Ziziphus jujuba is a typical xerophytic shrub. Clarifying the variation law of its root functional traits and the relationship with soil properties can enhance the understanding of plant resource acquisition strategies and provide a scientific basis for the sustainable management of Ziziphus jujuba shrub. Methods 24 Ziziphus jujuba shrubs in different habitats in Lincheng County, Xingtai City, the genuine medicinal material producing area of Ziziphus jujuba kernel, were selected as the research object. The morphology, configuration, chemical traits and soil properties of Ziziphus jujuba roots were determined. The variation law of Ziziphus jujuba root traits in different habitats was analyzed. The economic space of Ziziphus jujuba roots and the relationship between Ziziphus jujuba roots and environment was clarified. Important findings (1) The variation range of root configuration traits (branching ratio and branching intensity) of Ziziphus jujuba was significantly higher than that of morphological (average diameter and specific root length) and chemical (root nitrogen content and root carbon content) traits. At the intraspecies level, there was a two-dimensional root economic space for the root functional traits of Ziziphus jujuba. The first dimension was dominated by the trade-off between root diameter (tissue density) and specific root length (specific root area), representing the transformation of roots from autonomous foraging strategy to mycorrhizal cooperative nutrient acquisition strategy. The second dimension was composed of negatively correlated root tissue density (diameter) and root nitrogen (root carbon) content, which represented the trade-off dimension between root defense and resource acquisition. (2) The soil environment affected the resource acquisition of Ziziphus jujuba root. In the soil with high total phosphorus, total potassium or sand content and low pH, water content or organic carbon content, Ziziphus jujuba root tended to autonomous foraging strategy (developing higher specific root length and specific root area), on the contrary, Ziziphus jujuba root tended to cooperate with mycorrhizal to acquire resources. (3) Redundancy analysis showed that soil water content (9.29%), total phosphorus (6.12%), silt (3.87%) and clay content (2.96%) were the main environmental factors affecting the variation of root traits of Ziziphus jujuba. Under drought conditions, Ziziphus jujuba acquired resources by increasing the specific root length and specific root area. In a low-phosphorus environment, Ziziphus jujuba tended to increase its diameter to enhance its adaptability. Ziziphus jujuba achieved a balance between resource acquisition and survival defense through the synergistic adjustment of root traits, and its strategy was driven by environmental heterogeneity and long-term evolutionary screening. The research results provide a theoretical basis for the study of plant adaptation mechanism in arid areas.

Key words: root, functional traits, root economic space, soil properties