植物氮形态利用策略及对外来植物入侵性的影响

氮是影响外来植物入侵性的重要因素之一, 但相关研究多关注土壤氮水平的效应, 较少考虑氮形态的作用。为从土壤氮形态利用的角度阐释外来植物的入侵机制, 本文在植物氮形态利用策略分析的基础上, 综述了外来植物氮形态利用的偏好性及其对入侵性的影响。植物的氮形态利用策略有偏好性和可塑性两种, 这可能与植物对土壤氮形态特性的长期适应有关; 植物不仅可以对土壤氮形态做出响应, 而且还能改造土壤氮形态, 并对改变后的土壤氮形态做出反馈响应。很多外来植物入侵硝态氮占优势的干扰生境, 偏好硝态氮的外来植物与本地植物竞争硝态氮; 而偏好铵态氮的外来植物通过抑制土壤硝化作用, 营造铵态氮环境, 促进自身生长, 同时抑制偏好硝态氮的本地植物生长。然而, 植物氮形态利用策略不是一成不变的, 而是受多种生物和非生物因素共同作用影响的复杂过程, 今后应加强多因素交互作用对外来入侵植物氮形态利用策略的影响及机制研究, 更好地揭示氮形态利用策略, 尤其是氮形态利用的可塑性与外来植物入侵性的关系。

Plant strategies for nitrogen acquisition and their effects on exotic plant invasions

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.