Paris James C, Baxter Colden V, Bellmore J Ryan, Benjamin Joseph R
Department of Biological Sciences, Idaho State University, Pocatello, Idaho, USA.
Pacific Northwest Research Station, US Forest Service, Juneau, Alaska, USA.
Ecol Appl. 2025 Jan;35(1):e3076. doi: 10.1002/eap.3076. Epub 2024 Dec 3.
Food webs vary in space and time. The structure and spatial arrangement of food webs are theorized to mediate temporal dynamics of energy flow, but empirical corroboration in intermediate-scale landscapes is scarce. River-floodplain landscapes encompass a mosaic of aquatic habitat patches and food webs, supporting a variety of aquatic consumers of conservation concern. How the structure and productivity of these patch-scale food webs change through time, and how floodplain restoration influences their dynamics, are unevaluated. We measured productivity and food-web dynamics across a mosaic of main-channel and side-channel habitats of the Methow River, WA, USA, during two study years (2009-2010; 2015-2016) and examined how food webs that sustained juvenile anadromous salmonids responded to habitat manipulation. By quantifying temporal variation in secondary production and organic matter flow across nontreated river-floodplain habitats and comparing that variation to a side channel treated with engineered logjams, we jointly confronted spatial food-web theory and assessed whether food-web dynamics in the treated side channel exceeded natural variation exhibited in nontreated habitats. We observed that organic matter flow through the more complex, main-channel food web was similar between study years, whereas organic matter flow through the simpler, side-channel food webs changed up to ~4-fold. In the side channel treated with engineered logjams, production of benthic invertebrates and juvenile salmonids increased between study years by 2× and 4×, respectively; however, these changes did not surpass the temporal variation observed in untreated habitats. For instance, juvenile salmonid production rose 17-fold in one untreated side-channel habitat, and natural aggregation of large wood in another coincided with a shift to community and food-web dominance by juvenile salmonids. Our findings suggest that interannual dynamism in material flux across floodplain habitat mosaics is interrelated with patchiness in food-web complexity and may overshadow the ecological responses to localized river restoration. Although this dynamism may inhibit detection of the ecological effects of river restoration, it may also act to stabilize aquatic ecosystems and buffer salmon and other species of conservation concern in the long term. As such, natural, landscape-level patchiness and dynamism in food webs should be integrated into conceptual foundations of process-based, river restoration.
食物网在空间和时间上存在差异。食物网的结构和空间布局被认为会调节能量流动的时间动态，但在中等尺度景观中的实证支持却很匮乏。河流洪泛区景观包含水生栖息地斑块和食物网的镶嵌体，为各种受保护的水生消费者提供了生存环境。这些斑块尺度的食物网的结构和生产力如何随时间变化，以及洪泛区恢复如何影响其动态，目前尚未得到评估。在两个研究年份（2009 - 2010年；2015 - 2016年）期间，我们测量了美国华盛顿州梅索河主河道和侧河道栖息地镶嵌体中的生产力和食物网动态，并研究了维持幼年溯河产卵鲑鱼生存的食物网如何对栖息地操纵做出反应。通过量化未处理的河流洪泛区栖息地中次级生产和有机物质流动的时间变化，并将这种变化与用工程木堰处理的侧河道进行比较，我们共同验证了空间食物网理论，并评估了处理后的侧河道中的食物网动态是否超过了未处理栖息地中表现出的自然变化。我们观察到，在不同研究年份之间，流经更复杂的主河道食物网的有机物质流动情况相似，而流经较简单的侧河道食物网的有机物质流动变化高达约4倍。在用工程木堰处理的侧河道中，底栖无脊椎动物和幼年鲑鱼的产量在不同研究年份之间分别增加了2倍和4倍；然而，这些变化并未超过在未处理栖息地中观察到的时间变化。例如，在一个未处理的侧河道栖息地中，幼年鲑鱼的产量增长了17倍，而在另一个栖息地中，大型木材的自然聚集与幼年鲑鱼在群落和食物网中占据主导地位的转变同时发生。我们的研究结果表明，洪泛区栖息地镶嵌体中物质通量的年际动态与食物网复杂性的斑块性相互关联，可能会掩盖对局部河流恢复的生态反应。尽管这种动态可能会抑制对河流恢复生态效应的检测，但从长远来看，它也可能起到稳定水生生态系统以及缓冲鲑鱼和其他受保护物种的作用。因此，食物网中自然的、景观尺度的斑块性和动态性应纳入基于过程的河流恢复的概念基础中。
