生境异质性及源株密度对互花米草入侵力的影响

外来物种互花米草(Spartina alterniflora)被引种到我国海岸带后,已带来一系列生态危害,严重影响了入侵地生态系统结构和功能,深入了解其入侵机制是实施有效控制的基础和理论依据。长江口的滩涂湿地是我国典型的异质潮滩,拥有多种生境。为了探究异质潮滩环境中互花米草初始源株对其入侵力的影响,研究通过野外移栽实验,模拟不同源株密度,探讨潮滩湿地生境异质性及源株密度对互花米草定居、生长和扩散的影响。结果表明:1)生境异质性及源株密度均对互花米草存活率、株高及种群增长率有极显著影响(P0.01)。2)至生长季末,植被区内互花米草存活率、株高均显著高于前沿光滩(P0.05)。此外,淤泥质潮滩植被区内互花米草株高、种群增长率也显著高于粉砂质潮滩植被区(P0.05)。3)互花米草入侵植被区不受源株密度的限制,但随源株密度增加,互花米草种群增长率显著降低(P0.05),而株高无显著差异(P0.05);在光滩区,只有高源株密度才可入侵成功。4)异质生境的冲淤动态、淹水时间和淹水深度是影响互花米草存活和生长的主要环境因子。丰富了河口湿地互花米草入侵力的机理研究,也为我国开展互花米草防控及海岸带保护、修复和管理提供了科学依据,具有重要的理论和实践意义。

Effects of habitat heterogeneity and ortet density on the invasiveness of Spartina alterniflora

After being introduced into China''s coastal zone, the exotic species, Spartina alterniflora, has resulted in a series of ecological risks and seriously influenced the structure and function of the native ecosystem. Understanding the invasion mechanisms of S. alterniflora is the theoretical basis for its effective control. The estuarine wetland in the Yangtze Estuary, China, is a typical heterogeneous tidal flat with a variety of habitats. In this study, the effects of habitat heterogeneity and ortet density on the colonization, growth, and dispersal of S. alterniflora were studied using field experiments. The results were as follows:1) habitat heterogeneity and ortet density have significant effects on the survival rate, plant height, and population growth rate of S. alterniflora (P < 0.01); 2) at the end of the growing season, the survival rate and height of S. alterniflora in the vegetation area were significantly higher than that in the mudflat (P < 0.05). In addition, the height and population growth rate of S. alterniflora in the muddy tidal flat were significantly higher than that in the silty tidal flat (P < 0.05); 3) the invasion of S. alterniflora in the vegetation area was not limited by ortet density. The growth rate of the S. alterniflora population in vegetation area decreased significantly with increased ortet density (P < 0.05), but the plant height had no significant difference (P > 0.05). In addition, only the higher density S. alterniflora rhizomes could invade the mudflat successfully; 4) the sediment disturbance regimes, flooding time, and flooding depth are the key environmental factors that affected S. alterniflora survival and growth. This study enhances the understanding of S. alterniflora invasive mechanisms in coastal wetlands, and provides a scientific basis for the control of S. alterniflora, as well as the protection, restoration, and management of the coastal zone in China.