Nitrogen concentration in leaf of the three alien plants was subjected to different nutrient supplies.

N1: Low nitrogen supply (1 mmol L-1); N2: Intermediate nitrogen supply (4 mmol L-1); N3: High nitrogen supply (8 mmol L-1); P1: Low phosphorus supply (0.15 mmol L-1); P2: Intermediate phosphorus supply (0.6 mmol L-1); P3: High phosphorus supply (1.2 mmol L-1). Values are means ± SE. Bars with different lowercase letters denote significant differences (P < 0.05).