Schrama Maarten, van der Plas Fons, Berg Matty P, Olff Han
Institute for Environmental Science, University of Leiden, 2333 CC, Leiden, The Netherlands.
Soil and Ecosystem Ecology Group, University of Manchester, Michael Smith Building, Oxford Road, M13 9PT, Manchester, UK.
J Anim Ecol. 2017 Jan;86(1):158-169. doi: 10.1111/1365-2656.12602. Epub 2016 Nov 17.
Terrestrial ecosystems are characterized by a strong functional connection between the green (plant-herbivore-based) and brown (detritus-detritivore-based) parts of the food web, which both develop over successional time. However, the interlinked changes in green and brown food web diversity patterns in relation to key ecosystem processes are rarely studied. Here, we demonstrate changes in species richness, diversity and evenness over a wide range of invertebrate green and brown trophic groups during 100 years of primary succession in a saltmarsh ecosystem, using a well-calibrated chronosequence. We contrast two hypotheses on the relationship between green and brown food web diversity across succession: (i) 'coupled diversity hypothesis', which predicts that all trophic groups covary similarly with the main drivers of successional ecosystem assembly vs. (ii) the 'decoupled diversity hypothesis', where green and brown trophic groups diversity respond to different drivers during succession. We found that, while species richness for plants and invertebrate herbivores (green web groups) both peaked at intermediate productivity and successional age, the diversity of macrodetritivores, microarthropod microbivores and secondary consumers (brown web groups) continuously increased towards the latest successional stages. These results suggest that green web trophic groups are mainly driven by vegetation parameters, such as the amount of bare soil, vegetation biomass production and vegetation height, while brown web trophic groups are mostly driven by the production and standing stock of dead organic material and soil development. Our results show that plant diversity cannot simply be used as a proxy for the diversity of all other species groups that drive ecosystem functioning, as brown and green diversity components in our ecosystem responded differently to successional gradients.
陆地生态系统的特点是食物网的绿色部分（以植物-食草动物为基础）和棕色部分（以碎屑-碎屑食性动物为基础）之间存在紧密的功能联系，这两部分都在演替过程中发展。然而，关于绿色和棕色食物网多样性模式与关键生态系统过程相关的相互关联变化却很少被研究。在这里，我们利用一个校准良好的时间序列，展示了盐沼生态系统在100年的原生演替过程中，广泛的无脊椎动物绿色和棕色营养级组的物种丰富度、多样性和均匀度的变化。我们对比了关于演替过程中绿色和棕色食物网多样性关系的两种假设：（i）“耦合多样性假设”，该假设预测所有营养级组与演替生态系统组装的主要驱动因素有相似的共变关系，与（ii）“解耦多样性假设”，即绿色和棕色营养级组的多样性在演替过程中对不同的驱动因素做出反应。我们发现，虽然植物和无脊椎动物食草动物（绿色食物网组）的物种丰富度在中等生产力和演替年龄时都达到峰值，但大型碎屑食性动物、微型节肢动物微生物食性动物和二级消费者（棕色食物网组）的多样性在演替的最新阶段持续增加。这些结果表明，绿色食物网营养级组主要受植被参数驱动，如裸土量、植被生物量生产和植被高度，而棕色食物网营养级组主要受死亡有机物质的生产和存量以及土壤发育驱动。我们的结果表明，植物多样性不能简单地用作驱动生态系统功能的所有其他物种组多样性的代理，因为我们生态系统中的棕色和绿色多样性成分对演替梯度的反应不同。
