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Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams
Citation:
Larson, C., P. Engelken, D. McCullough, AND E. Benbow. Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams. CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES. NRC Research Press, Ottawa, Canada, 80(2):298-312, (2023). https://doi.org/10.1139/cjfas-2022-0127
Impact/Purpose:
Emerald Ash Borer (EAB) is a forest invasive insect that has killed millions of ash trees since its introduction. We surveyed watersheds in Michigan across EAB’s range expansion to determine the effect of EAB-caused ash tree death on streams. Woody debris and leaf litter was not affected by EAB, but stream sites downstream of EAB-related canopy gaps had lower macroinvertebrate diversity than sites upstream and at the gaps, and EAB-related canopy gaps alter leaf associated bacterial communities. Overall, these findings reveal EAB invasion negatively impacts stream ecosystems. These results inform stream and forest managers as EAB spreads and causes more tree death in riparian zones, affecting stream biodiversity.
Description:
Emerald ash borer (EAB) has killed millions of ash trees in the United States and Canada, yet impacts on terrestrial-aquatic linkages are largely unknown. Ash tree death along streams creates canopy gaps, increasing light to riparian plants and potentially affecting organic matter subsidies. Six EAB-related canopy gaps along streams across a gradient of timing of EAB invasion in Michigan were characterized for coarse woody material (CWM), terrestrial and aquatic leaf litter and their associated bacterial communities, and macroinvertebrates upstream, downstream, and at the center of the gap. Stream sites downstream of EAB-related canopy gaps had significantly lower dissolved oxygen and macroinvertebrate diversity than sites upstream and at the gaps. Yet there was no difference in CWM or aquatic leaf litter, likely due to downstream movement of organic matter from upstream riparian sources. Low abundance bacterial amplicon sequence variants unique to gap or forest were detected in leaves and leaf litter, suggesting that EAB-related canopy gaps altered leaf-associated bacterial communities. Overall, EAB invasion indirectly impacted some variables, while organic matter dynamics were resistant to change.
URLs/Downloads:
DOI: Emerald ash borer invasion of riparian forests alters organic matter and bacterial subsidies to south Michigan headwater streams
https://cdnsciencepub.com/doi/full/10.1139/cjfas-2022-0127