Shallow resource foraging and deep-water shift: plant-soil feedbacks sustain transient coexistence during Phyllostachys edulis invasion

• Stable isotopes and niche overlap detect P. edulis effects on broad-leaved forests. • P. edulis mostly takes up shallow, nutrient-rich water via its well-developed root. • Q. acutissima shifts water uptake from shallow to deep soil due to P. edulis invasion. • P. edulis invasion success hinges on resource capture and heightened niche overlap. The invasion of Phyllostachys edulis leading to the gradual replacement of broad-leaved forest species by P. edulis has occurred more frequently in recent years. Thus, it is critical to understand and quantify how invasive P. edulis affects water-soluble nutrients in broad-leaved forests. In this study, we quantified the water sources of P. edulis and the broad-leaves forest species Quercus acutissima using stable isotope technology and analyzed the impact of invasion on their strategies for uptake of water-soluble nutrients. We observed that the soil water storage capacity progressively decreased, while the water storage capacity of litter proportionally increased with invasion intensity. Phyllostachys edulis mostly took up shallow soil water with high nutrient content through its well-developed shallow root system and exhibited a consequently high resource acquisition rate. Q. acutissima that originally absorbed shallow soil water were forced to uptake water from deep and stable water sources (with low water-soluble nutrient content) after being invaded by P. edulis , and exhibited positive feedback adaptation. After P . edulis invasion, although the resource acquisition ratio of Q . acutissima was low, a stable water source can ensure a sustained water supply for Q. acutissima . The ecological niche overlap index also indicated that P. edulis has a high ecological niche competitive advantage in shallow layers owing to its strong tillering ability. Therefore, the invasion of Q. acutissima by P . edulis was achieved through the capture of resources by its root systems and high ecological niche overlap. These findings suggest plant-soil positive feedback temporarily maintaining stable states in the invasion of ecosystems.