Aquatic Sciences

, 80:37 | Cite as

Wildfire and debris flows affect prey subsidies with implications for riparian and riverine predators

  • Hannah E. HarrisEmail author
  • Colden V. Baxter
  • John M. Davis
Research Article


Ecosystems are connected through fluxes of nutrients, organic matter, and organisms. Disturbances that alter structure and function of one ecosystem may have consequences for other linked ecosystems. We investigated how wildfire and subsequent debris flows altered fluxes of invertebrates from tributaries in the Salmon River Basin, Idaho, USA. We compared fluxes of invertebrates downstream through drift and laterally via insect emergence from streams with varying disturbance histories (unburned, burned, and burned + debris flow) during two summers (3–4 years post fire and 2–3 years post debris flow). We observed that the combination of wildfire and debris flow increased the biomass export of invertebrates from tributaries to main-stem ecosystems 2–3 × compared to other streams. In contrast, aquatic insect emergence did not differ in magnitude among streams of different disturbance histories, but instead diverged in timing. Underwater surveys indicated trout in the main-stem river selected confluence habitats, with a tendency for stronger selection of confluences with burned streams. In a behavioral comparison between confluence and non-confluence habitats, rates of agonistic behavior were 4–6 × higher in confluence areas, indicating that confluences may be worth defending. Abundances of web-spinning spiders that depend on emerging insects did not vary with disturbance history in early-mid summer, but tended to be highest in riparian areas along burned streams by August. Because wildfire and debris flows are predicted to increase, our results elucidate potential pathways by which altered disturbance regimes may affect coupled aquatic-terrestrial ecosystems.


Invertebrate drift Spatial subsidies Insect emergence Food webs River confluences 



This research was supported by United States Forest Service Payette National Forest, National Science Foundation’s Experimental Program to Stimulate Competitive Research in Idaho (EPS-08-14387), and a University Research Committee Grant at Idaho State University. We thank R. Nelson and C. Zurstadt of the Payette National Forest and R. Arkle and D. Pilliod of the United States Geological Survey for help with research logistics. We thank M. Apple A. Bell, R. Blackadar, S. Collins, J. Cornell, K. Heinrich, M. Schenk, and A. Steele for research assistance, and T. Bowyer and K. Aho for statistical advice.


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Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  1. 1.Stream Ecology Center, Department of Biological SciencesIdaho State UniversityPocatelloUSA
  2. 2.Idaho Department of Environmental QualityPocatelloUSA

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