Aims <p>This study investigates the differences in root traits of <i>Ligustrum lucidum</i>, a subtropical evergreen tree, and their responses to the combined stresses of soil moisture and nutrient availability in karst regions.</p> Methods <p>Root and soil samples from <i>Ligustrum lucidum</i> were collected from two distinct geological environments—sandy shale and limestone areas. The root system was classified, and by analyzing the correlations between the root functional traits and the physical and chemical properties of the soils, to identify patterns of root trait variation under varying environmental conditions.</p> Results <p>Results revealed that soil moisture and nutrient levels were significantly lower in limestone areas compared to sandy shale areas. There are significant differences in root functional traits between the sandy shale area and the limestone area. In sandy shale areas, RD, RTD, and RDMC were larger than those in limestone areas. Two contrasting patterns of resource utilization associated with root traits were identified.</p> Conclusions <p>The root functional traits of <i>Ligustrum lucidum</i> exhibit significant plasticity in responses to soil nutrient and water availability under environmental stresses, varying mainly in relation to soil nutrient availability. Contrary to traditional concepts, <i>Ligustrum lucidum</i> root trait combinations suggest enhanced resource uptake efficiency, optimizing nutrient and water foraging in limestone areas with poorer soil conditions, and promoting structural investment, improving the retention rate of water and nutrients in nutrient-rich, moisture-abundant sandy shale areas. These findings highlight the plasticity of root trait responses of <i>Ligustrum lucidum</i> to heterogeneous karst soil conditions.</p>