Root-Mediated Competition: Nutrient Acquisition Drives the Competitive Suppression of Wheat by Aegilops tauschii

Abstract Root interactions play a key role in shaping plant community structure and the competitive ability of invasive plants, influencing both resource competition and secretion-mediated interactions. To examine how root interactions influence the competitive relationship between the invasive plant Aegilops tauschii and wheat (Triticum aestivum), we manipulated root competition in pot experiments using no-partition, mesh-partition, and plastic-partition treatments. Results showed that root interactions significantly affected the growth and leaf nutrient/chlorophyll status of both A. tauschii and wheat. A. tauschii showed higher RMR together with higher leaf N, P, and chlorophyll contents, which may have contributed to greater biomass accumulation. In contrast, wheat’s growth, nutrient uptake, and chlorophyll levels were notably reduced. Competition indices revealed that the corrected index of relative competition intensity (CRCI) values for A. tauschii were all less than 0, indicating that mixed-culture conditions favored A. tauschii. Conversely, CRCI values for wheat were all greater than 0, and the inhibitory effect in the no-partition treatment was significantly stronger than in the mesh-partition treatment, suggesting that unrestricted belowground interaction may intensify the competitive suppression of wheat by A. tauschii. Therefore, root interactions may intensify wheat suppression by enhancing the morphological development, leaf nutrient contents, and chlorophyll accumulation of A. tauschii. A. tauschii gains a competitive advantage over wheat through root-mediated nutrient acquisition and interaction mechanisms.