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Quantifying the variation and coordination patterns of plant functional traits across different organs under environmental changes is crucial for understanding plant invasion and adaptation mechanisms. This study employed a space-for-time substitution experiment to compare the differential responses of root and leaf functional traits and their coordination in the invasive plant Alternanthera philoxeroides and the native plant Ludwigia peploides to nitrogen addition during different invasion degree. The results showed that: (1) nitrogen addition promoted the growth of both species, with A. philoxeroides exhibited greater biomass sensitivity. Compared to the positive effects of nitrogen fertilization, nitrogen addition facilitated A. philoxeroides in displacing L. peploides in communities with 50% (2 A. philoxeroides seedlings) and 75% (3 A. philoxeroides seedlings) invasion degree. (2) invasion degree, nitrogen addition, and their interaction significantly influenced most root and leaf traits of both species. But the two species differed markedly in their response of root and leaf traits to environmental factors. (3) The correlations between root traits, leaf traits, and total biomass were stronger in A. philoxeroides than in L. peploides, as were the linkages between root and leaf traits. Under environmental changes, the two species exhibited distinct adaptive strategies in root and leaf traits, with A. philoxeroides's trait advantages likely contributing to its invasion success. In conclusion, our study demonstrates that nitrogen deposition facilitates alien plant invasion, particularly in mixed communities experiencing moderate to severe invasion.
Li et al. (Mon,) studied this question.