Cascading impacts of overstory structure in managed forests on understory structure, microclimate conditions, and Ixodes scapularis (Acari: Ixodidae) densities

Stephanie N Hurd; Laura S Kenefic; Jessica E Leahy; Carly C Sponarski; Allison M Gardner

doi:10.1093/jme/tjae030

Cascading impacts of overstory structure in managed forests on understory structure, microclimate conditions, and Ixodes scapularis (Acari: Ixodidae) densities

J Med Entomol. 2024 Mar 16:tjae030. doi: 10.1093/jme/tjae030. Online ahead of print.

Authors

Stephanie N Hurd¹, Laura S Kenefic², Jessica E Leahy³, Carly C Sponarski⁴, Allison M Gardner¹

Affiliations

¹ Department of Ecology and Environmental Sciences, School of Biology and Ecology, University of Maine, 5722 Deering Hall, Orono, ME 04469, USA.
² USDA Forest Service, Northern Research Station, 54 Government Road, Bradley, ME 04411, USA.
³ Department of Human Dimensions of Natural Resources, School of Forest Resources, University of Maine, 5755 Nutting Hall, Orono, ME 04469, USA.
⁴ Canadian Forest Service, Northern Forestry Centre, 5320 122 St. NW, Edmonton, AB T6H 3S5, Canada.

PMID: 38491994
DOI: 10.1093/jme/tjae030

Abstract

Forest management practices designed to meet varied landowner objectives affect wildlife habitat and may interrupt the life-cycle stages of disease vectors, including the black-legged tick, Ixodes scapularis Say (Acari: Ixodidae). Ixodes scapularis transmits multiple pathogens including Borrelia burgdorferi, the causative agent of Lyme disease, which is the most common tick-borne disease in the United States. There is evidence that a range of active forest management practices (e.g., invasive plant removal, prescribed burning) can alter tick densities and pathogen transmission. However, few studies have investigated relationships between forest stand structural variables commonly manipulated by timber harvesting and tick ecology. Foresters may harvest timber to create certain forest structural conditions like the mean number of trees, or basal area, per hectare. This study used a spatially replicated experiment in a blocked design to compare forest stands with a range of overstory structures and document variations in the midstory, understory, and forest floor, as well as microclimate conditions within tick off-host habitat. Greater numbers of trees or basal area per hectare correlated with greater canopy closure but less understory cover, stabilized microclimate temperature, higher microclimate humidity, and greater I. scapularis nymph densities. A random forest model identified understory forest structure as the strongest predictor of nymph densities. There was no relationship between the number of trees or basal area per hectare and daily deer (Odocoileus virginianus Zimmermann) activity or nymphal infection prevalence. These findings provide a deeper understanding of tick-habitat associations within a forest stand and have the potential to inform forest management decisions.

Keywords: Borrelia burgdorferi; black-legged tick; silviculture; tick-borne pathogen; timber harvest.

Abstract

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