National Institute of Water and Atmospheric Research, Gate 10 Silverdale Road, Hamilton 3216, New Zealand.
National Institute of Water and Atmospheric Research, Gate 10 Silverdale Road, Hamilton 3216, New Zealand.
Sci Total Environ. 2019 Apr 1;659:1370-1381. doi: 10.1016/j.scitotenv.2018.12.277. Epub 2018 Dec 19.
Understanding how inter-specific variation in functional traits affects native and non-native species responses to stream disturbances, is necessary to inform management strategies, providing tools for biomonitoring, conservation and restoration. This study used a functional trait approach to characterise the responses of macrophyte assemblages to reach-scale disturbances (measured by lack of riparian shading, altered hydromorphology and eutrophication), from 97 wadeable stream sites in an agriculturally impacted region of New Zealand. To determine whether macrophyte assemblages differed due to disturbances, we examined multidimensional assemblage functional structure in relation to eleven functional traits and further related two functional diversity indices (entropy and originality) to disturbances. Macrophyte assemblages showed distinct patterns in response to disturbances, with riparian shading and hydromorphological conditions being the strongest variables shaping macrophyte functional structure. In the multidimensional space, most of the non-native species were associated with disturbed conditions. These species had traits allowing faster colonisation rates (higher number of reproductive organs and larger root-rhizome system) and superior competitive abilities for resources (tall and dense canopy, heterophylly and greater preferences for light and nitrogen). In addition, lack of riparian shading increased the abundance of functionally distinct species (i.e. entropy), and eutrophication resulted in the growth of functionally unique species (i.e. originality). We demonstrated that stream reach-scale habitat disturbances were associated to a dominance of more productive species, equating to a greater abundance of non-native species. This, can result in a displacement of native species, habitat alterations, and changes to higher trophic level assemblages. Our results suggests that reach-scale management efforts such as the conservation and restoration of riparian vegetation that provides substantial shading and hydromorphologically diverse in-stream habitat, would have beneficial direct and indirect effects on ecosystem functioning, and contribute to the mitigation of land-use impacts.
理解功能性状在种间变异如何影响本地种和非本地种对溪流干扰的响应，对于指导管理策略是必要的，为生物监测、保护和恢复提供了工具。本研究采用功能性状方法，从新西兰一个受农业影响地区的 97 个可涉水溪流站点，描述了大型植物群落对沿程尺度干扰（由缺乏河岸遮荫、改变水力学形态和富营养化来衡量）的响应。为了确定大型植物群落是否因干扰而不同，我们检查了多维集合功能结构与十一个功能性状的关系，并进一步将两个功能多样性指数（熵和独特性）与干扰联系起来。大型植物群落对干扰表现出明显的模式，河岸遮荫和水力学条件是塑造大型植物功能结构的最强变量。在多维空间中，大多数非本地物种与受干扰的条件有关。这些物种具有允许更快的定植率的特征（更多的生殖器官和更大的根-根茎系统）和更高的资源竞争能力（高大而密集的树冠、异形叶性和对光和氮的更大偏好）。此外，缺乏河岸遮荫增加了功能上不同的物种（即熵）的丰度，而富营养化导致功能独特的物种（即独特性）的生长。我们表明，溪流沿程尺度的栖息地干扰与更具生产力的物种的优势有关，这等同于更多非本地物种的丰度。这可能导致本地物种的取代、栖息地的改变和更高营养级别的群落的变化。我们的结果表明，沿程尺度的管理措施，如保护和恢复提供大量遮荫和水力学形态多样的河岸植被，将对生态系统功能产生直接和间接的有益影响，并有助于减轻土地利用的影响。
