BACKGROUND Recent studies of anadromous salmon (Oncorhynchus spp.) on the Pacific Coast of North America indicate an important and previously unrecognized role of salmonid nutrients to terrestrial biota. However, the extent of this uptake by primary producers and consumers and the influences on community structure remain poorly described. We examine here the contribution of salmon nutrients to multiple taxa of riparian vegetation (Blechnum spicant, Menziesii ferruginea, Oplopanax horridus, Rubus spectabilis, Vaccinium alaskaense, V. parvifolium, Tsuga heterophylla) and measure foliar delta15N, total %N and plant community structure at two geographically separated watersheds in coastal British Columbia. To reduce potentially confounding effects of precipitation, substrate and other abiotic variables, we made comparisons across a sharp ecological boundary of salmon density that resulted from a waterfall barrier to salmon migration. RESULTS delta15N and %N in foliage, and %cover of soil nitrogen indicators differed across the waterfall barrier to salmon at each watershed. delta15N values were enriched by 1.4 per thousand to 9.0 per thousand below the falls depending on species and watershed, providing a relative contribution of marine-derived nitrogen (MDN) to vegetation of 10% to 60%. %N in foliar tissues was slightly higher below the falls, with the majority of variance occurring between vegetation species. Community structure also differed with higher incidence of nitrogen-rich soil indicator species below the waterfalls. CONCLUSIONS Measures of delta15N, %N and vegetation cover indicate a consistent difference in the riparian community across a sharp ecological boundary of salmon density. The additional N source that salmon provide to nitrogen-limited habitats appears to have significant impacts on the N budget of riparian vegetation, which may increase primary productivity, and result in community shifts between sites with and without salmon access. This, in turn, may have cascading ecosystem effects in forests adjacent to salmon streams.

中文翻译：

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跨越鲑鱼密度的尖锐生态边界的河岸植物群落的氮吸收。


背景最近对北美太平洋沿岸溯河产卵鲑鱼（Oncorhynchus spp.）的研究表明，鲑鱼营养物质对陆地生物群具有重要且之前未被认识到的作用。然而，初级生产者和消费者的这种吸收程度以及对社区结构的影响仍然很少被描述。我们在此研究了鲑鱼营养物质对河岸植被多个类群（Blechnum spicant、Menziesii ferruginea、Olopopanax horridus、Rubus spectabilis、Vaccinium alaskaense、V. parvifolium、Tsugahetugahettophylla）的贡献，并测量了叶 delta15N、总氮百分比和植物群落结构不列颠哥伦比亚省沿海两个地理上分离的流域。为了减少降水、底物和其他非生物变量的潜在混杂影响，我们对鲑鱼迁徙的瀑布屏障造成的鲑鱼密度的尖锐生态边界进行了比较。结果 叶子中的 delta15N 和 %N 以及土壤氮覆盖率指标在每个流域的鲑鱼瀑布屏障上都不同。根据物种和流域的不同，瀑布下方的 delta15N 值富集了 1.4% 至 9.0%，海洋源氮 (MDN) 对植被的相对贡献为 10% 至 60%。叶组织中的%N 略高于瀑布下方，大部分差异发生在植被物种之间。群落结构也有所不同，瀑布下方富氮土壤指示物种的发生率较高。结论 delta15N、%N 和植被覆盖度的测量表明，在鲑鱼密度的尖锐生态边界上，河岸群落存在一致的差异。 鲑鱼为氮限制栖息地提供的额外氮源似乎对河岸植被的氮预算产生重大影响，这可能会提高初级生产力，并导致有和没有鲑鱼进入的地点之间的群落转移。反过来，这可能会对鲑鱼溪流附近的森林产生连锁生态系统影响。