异质生境中空心莲子草化学计量特征与群落可入侵性关系研究

The relationship between invasiveness and invasibility has been the core content for understanding the mechanism and effect of biological invasions. Previous related studies are mainly focused on the structure, species diversity and propagule pressure of invaded community in single habitat, however, the ecological stoichiometry could integrate all levels of molecules, organisms and ecosystems by analyzing the balance relationships among multiple chemical elements in ecological processes, thus deeply states the homeostasis mechanism of biological invasions. In this study, we will investigate the terrestrial and aquatic communities which invaded by alligator weed, Alternanthera philoxeroides in China, and collect the heterogeneous habitat factors, stoichiometric ratio of important life element of invasive-main native accompanying plant species, structure characteristics of invaded community. We analyze the different allocation patterns of C (carbon), N (nitrogen), P (phosphorus) in invasive-native species and environmental determinants, meanwhile evaluate the effect of ecological stoichiometriy of A. philoxeroides on invasibility by using mathematical statistics and quantitative ecological methods. These findings will contribute to clarifying the coupling relationships of ‘heterogeneous habitats - invasive plant chemical metrology -invasibility’ at multi ecological levels, and are also crucial for predicting dynamic changes of invaded community and preventing biological invasions.

外来种的入侵性及本土群落的可入侵性是研究生物入侵机制和生态效应的核心内容。以往关于群落可入侵性的研究多集中于单一生境中入侵群落结构、物种多样性及繁殖体压力等宏观方面；而生态化学计量学通过分析生态过程中多重化学元素的平衡关系能够将分子、有机体和生态系统各层次统一起来，从而深度明晰“入侵性-可入侵性”的内稳态机制。本项目以广泛入侵中国的水、陆两生型杂草空心莲子草为例，拟通过野外大空间尺度调查和取样，采集异质性生境因子、空心莲子草及其主要本土伴生植物的重要生命元素化学计量比、入侵群落结构特征等关键指标，利用统计学及数量生态学方法分析入侵种和本土种体内C、N、P等化学元素分配格局的差异及其主导性环境因素、空心莲子草生态化学计量特征对群落可入侵性的影响。研究结果将在多生态层次上阐明“异质生境-入侵植物化学计量-群落可入侵性”耦合关系，对于预测入侵群落动态变化及入侵防治具有重要的指导意义。

生境异质性表征了环境因子在空间分布上的不均匀性及复杂性，入侵/本土植物对于生境中各类养分的需求及吸收能力存在差异，导致植物体内碳（C）、氮（N）、磷（P）含量及其计量比不同，进而影响群落可入侵性。基于生态化学计量学探究群落可入侵性及其驱动因子，有助于揭示入侵系统结构特征及功能动态变化的过程和机制。本项目以水、陆两栖型入侵植物空心莲子草为研究对象，通过设置104个沿纬度梯度（N21°-N37°）的入侵群落样地，采用回归分析、典范对应分析（CCA）和冗余分析（RDA）等方法探讨了异质生境中空心莲子草群落结构、入侵/本土植物生态化学计量特征差异、生态化学计量比-群落可入侵性关系及其环境驱动力，主要结论如下：（1）陆生空心莲子草入侵盖度、分枝数随物种多样性上升而降低；水生空心莲子草群落可划分为6组群丛类型及4类功能群；陆生空心莲子草群落稳定性随经度、纬度上升而增加，随年均温、年均降雨量上升而下降，水生群落稳定性变化格局与之相反。（2）陆生空心莲子草C:N随纬度及土壤铵态氮增加呈“先上升-后下降”趋势、随土壤硝态氮增加而降低；其C:P随纬度、经度增加而下降、随土壤硝态氮增加而上升；专食性天敌莲草直胸跳甲的C及C:N随陆生空心莲子草C上升而增加。（3）相对于本土伴生种双穗雀稗及本土同属种莲子草而言，空心莲子草具有更强的N吸收能力及更为稳定的N:P，但本土种生态化学计量比对异质生境的响应程度较高，其选择以“生长竞争策略”应对入侵，从而实现与空心莲子草的广泛共存；空心莲子草C:N越高，群落可入侵性越高；空心莲子草N:P越高，群落可入侵性越低。这些结果将生态系统的各层次统一起来，阐明了“环境-入侵植物化学计量-群落可入侵性”耦合关系，有助于预测全球环境变化下的入侵群落动态变化，为制定更具针对性的外来生物入侵防治策略提供理论基础，也可为解释群落构建、物种共存以及生物多样性维持机制提供新视角。