Abstract:

Aim: Available nitrogen is a major factor that influences invasion success of exotic plants. However, our understanding behind the effects of different forms of soil nitrogen on exotic plant invasions remains inconclusive. To elucidate invasion mechanisms of exotic plants in context of soil nitrogen, we reviewed nitrogen form preferences of invasive plants and their effects on invasiveness in comparison to native plant strategies.
Progresses: Different plants have different nitrogen form acquisition strategies, including preference and plasticity, which may be associated with long-term adaption to characteristics of soil nitrogen form and occur at different scales. In addition, some plants can modulate soil nitrogen forms, and respond to altered soil nitrogen. Many invasive plants succeed in disturbed habitats where nitrate is the dominant form of soil nitrogen, as they prefer nitrate and compete for nitrate with co-occurring native plants. Whereas ammonium-preferring invasive plants may accumulate ammonium in soil by inhibiting soil nitrification, thereby facilitating their own growth and inhibiting native plant growth, further contributing to invasion success. However, plant strategies for nitrogen acquisition are not invariable and can be influenced by many biotic and abiotic factors and interactions.
Prospects: In future research we should study plant nitrogen acquisition strategies along with their ecological and evolutionary mechanisms in conjunction with ecosystem and environmental factors, especially plasticity of nitrogen form utilization and its relationship with invasiveness of exotic plants. In addition, mycorrhizal fungi may also affect plant utilization of different nitrogen forms, which is also worth studying.

Key words: adaptive evolution, exotic plant invasions, plant nitrogen form preference, plant strategies for acquiring different nitrogen forms, plasticity of nitrogen form utilization, soil nitrogen forms