Jackrel Sara L, Wootton J Timothy
Department of Ecology and Evolution, The University of Chicago, Chicago, Illinois, United States of America.
PLoS One. 2015 Nov 5;10(11):e0142362. doi: 10.1371/journal.pone.0142362. eCollection 2015.
Organismal diversity among and within species may affect ecosystem function with effects transmitting across ecosystem boundaries. Whether recipient communities adjust their composition, in turn, to maximize their function in response to changes in donor composition at these two scales of diversity is unknown. We use small stream communities that rely on riparian subsidies as a model system. We used leaf pack experiments to ask how variation in plants growing beside streams in the Olympic Peninsula of Washington State, USA affects stream communities via leaf subsidies. Leaves from red alder (Alnus rubra), vine maple (Acer cinereus), bigleaf maple (Acer macrophyllum) and western hemlock (Tsuga heterophylla) were assembled in leaf packs to contrast low versus high diversity, and deployed in streams to compare local versus non-local leaf sources at the among and within species scales. Leaves from individuals within species decomposed at varying rates; most notably thin leaves decomposed rapidly. Among deciduous species, vine maple decomposed most rapidly, harbored the least algal abundance, and supported the greatest diversity of aquatic invertebrates, while bigleaf maple was at the opposite extreme for these three metrics. Recipient communities decomposed leaves from local species rapidly: leaves from early successional plants decomposed rapidly in stream reaches surrounded by early successional forest and leaves from later successional plants decomposed rapidly adjacent to later successional forest. The species diversity of leaves inconsistently affected decomposition, algal abundance and invertebrate metrics. Intraspecific diversity of leaf packs also did not affect decomposition or invertebrate diversity. However, locally sourced alder leaves decomposed more rapidly and harbored greater levels of algae than leaves sourced from conspecifics growing in other areas on the Olympic Peninsula, but did not harbor greater aquatic invertebrate diversity. In contrast to alder, local intraspecific differences via decomposition, algal or invertebrate metrics were not observed consistently among maples. These results emphasize that biodiversity of riparian subsidies at the within and across species scale have the potential to affect aquatic ecosystems, although there are complex species-specific effects.
物种之间和物种内部的生物多样性可能会影响生态系统功能，其影响会跨越生态系统边界进行传递。目前尚不清楚接受群落是否会相应地调整其组成，以在这两种多样性尺度下，响应供体组成的变化而使自身功能最大化。我们使用依赖河岸补贴的小溪群落作为模型系统。我们通过叶包实验来探究美国华盛顿州奥林匹克半岛溪边生长的植物的多样性变化如何通过落叶补贴影响溪流群落。将红桤木（Alnus rubra）、藤枫（Acer cinereus）、大叶枫（Acer macrophyllum）和西部铁杉（Tsuga heterophylla）的叶子组装成叶包，以对比低多样性和高多样性，并投放到溪流中，在物种间和物种内尺度上比较本地与非本地叶源。物种内个体的叶子分解速率各不相同；最显著的是薄叶分解迅速。在落叶物种中，藤枫分解最快，藻类丰度最低，支持的水生无脊椎动物多样性最高，而大叶枫在这三个指标上则处于相反的极端。接受群落能快速分解本地物种的叶子：早期演替植物的叶子在被早期演替森林环绕的溪流河段中分解迅速，而后期演替植物的叶子在靠近后期演替森林的地方分解迅速。叶子的物种多样性对分解、藻类丰度和无脊椎动物指标的影响并不一致。叶包的种内多样性也不影响分解或无脊椎动物多样性。然而，与从奥林匹克半岛其他地区生长的同物种植物获取的叶子相比，本地来源的桤木叶分解更快，藻类含量更高，但水生无脊椎动物多样性并未更高。与桤木不同，在枫香中，通过分解、藻类或无脊椎动物指标并未始终观察到本地种内差异。这些结果强调，河岸补贴在物种内和物种间尺度上的生物多样性有可能影响水生生态系统，尽管存在复杂的物种特异性效应。
