Does Atmospheric Nitrogen Deposition Confer a Competitive Advantage to Invasive Bidens pilosa L. over Native Pterocypsela laciniata (Houtt.) Shih?

One of the key reasons for the success of invasive plants is the functional differences between invasive plants and native plants. However, atmospheric nitrogen deposition may disrupt the level of available nitrogen in soil and the functional differences between invasive plants and native plants, which may alter the colonization of invasive plants. Thus, there is a pressing necessity to examine the effects of atmospheric nitrogen deposition containing different nitrogen components on the functional differences between invasive plants and native plants. However, the progress made thus far in this field is not sufficiently detailed. This study aimed to elucidate the effects of artificially simulated nitrogen deposition containing different nitrogen components (i.e., nitrate, ammonium, urea, and mixed nitrogen) on the functional differences between the Asteraceae invasive plantBidens pilosaL. and the Asteraceae native plantPterocypsela laciniata(Houtt.) Shih. The study was conducted over a four-month period using a pot-competitive co-culture experiment. The growth performance ofP. laciniata, in particular with regard to the sunlight capture capacity (55.12% lower), plant supporting capacity (45.92% lower), leaf photosynthetic area (51.24% lower), and plant growth competitiveness (79.92% lower), may be significantly inhibited under co-cultivation condition in comparison to monoculture condition.Bidens pilosaexhibited a more pronounced competitive advantage overP. laciniata, particularly in terms of the sunlight capture capacity (129.43% higher), leaf photosynthetic capacity (40.06% higher), and enzymatic defense capacity under stress to oxidative stress (956.44% higher). The application of artificially simulated nitrogen deposition was found to facilitate the growth performance of monoculturalP. laciniata, particularly in terms of the sunlight capture capacity and leaf photosynthetic area.Bidens pilosaexhibited a more pronounced competitive advantage (the average value of the relative dominance index ofB. pilosais ≈ 0.8995) thanP. laciniataunder artificially simulated nitrogen deposition containing different nitrogen components, especially when treated with ammonium (the relative dominance index ofB. pilosais ≈ 0.9363) and mixed nitrogen (the relative dominance index ofB. pilosais ≈ 0.9328). Consequently, atmospheric nitrogen deposition, especially the increased relative proportion of ammonium in atmospheric nitrogen deposition, may facilitate the colonization ofB. pilosavia a stronger competitive advantage.