School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Parkville, VIC, Australia.
Department of Infrastructure Engineering, University of Melbourne, Parkville, VIC, Australia.
Oecologia. 2023 May;202(1):41-54. doi: 10.1007/s00442-023-05368-z. Epub 2023 May 3.
Resource supplementation can increase species richness and change the faunal composition of communities, but experiments have produced variable outcomes. An often overlooked element is that species richness can only increase if new taxa can disperse to resource-rich locations and invade established, local communities. We experimentally increased a basal resource (detritus) in six rivers in south-eastern Australia by driving wooden stakes into the riverbed to increase retention of detritus. Control sites were left untreated. Sites were located in agricultural sections with mostly cleared vegetation, but with intact (uncleared) reference sites upstream to provide sources of prospective colonists. We measured channel retentiveness and sampled benthic detritus and invertebrates before and after manipulation. We tested whether: greater retentiveness increased detritus densities, species richness and abundances and altered faunal composition; manipulation sites reached bio-equivalence with reference sites; new species arose from upstream reference areas; and whether outcomes were consistent across rivers. Only three rivers gained increases in detritus densities. All had low pre-existing amounts of in-stream wood compared with rivers that did not respond to treatment. Two rivers (Hughes Creek, Seven Creeks) gained higher species richness and invertebrate densities within 12 months and reached bio-equivalence with reference sites. In contrast, Turtons Creek showed species turnover through replacement of individuals. Only in Hughes Creek was there evidence of successful dispersal from the upstream reference area. The outcomes show that the effects of resource supplementation vary between rivers and suggest that pre-existing conditions (e.g. channel retentiveness) may cause these differences, providing clear evidence of context dependence.
资源补充可以增加物种丰富度并改变群落的动物区系组成，但实验结果却各不相同。一个经常被忽视的因素是，如果新的分类单元能够分散到资源丰富的地方并入侵已建立的当地群落，那么物种丰富度才会增加。我们通过将木桩打入河床来增加澳大利亚东南部六条河流中的基础资源（碎屑），从而在实验中增加了基本资源。对照点未进行处理。这些地点位于农业区，植被大部分被清除，但上游有完整（未清除）的参考点，为潜在的殖民者提供来源。我们在处理前后测量了通道的保留率，并对底栖碎屑和无脊椎动物进行了采样。我们测试了以下内容：保留率的增加是否会增加碎屑密度、物种丰富度和丰度并改变动物区系组成；处理点是否达到与参考点的生物等效性；新物种是否来自上游参考区；以及结果是否在不同河流中一致。只有三条河流增加了碎屑密度。与未对处理做出反应的河流相比，所有这些河流的溪流中现有的木材量都较低。在 12 个月内，两条河流（休斯溪和七溪）的物种丰富度和无脊椎动物密度增加，并达到了与参考点的生物等效性。相比之下，特顿溪则表现出个体替换的物种更替。只有在休斯溪，才有证据表明从上游参考区成功扩散。研究结果表明，资源补充的效果在不同河流之间存在差异，并表明存在先行条件（例如通道保留率）可能导致这些差异，从而为情境依赖性提供了明确的证据。
