Traffic patterns, more than adjacent land use, influence element content of roadside forbs for insect pollinators

Roadsides are targeted for restoration of pollinator-friendly plants. Yet, roads are sources of macronutrient, micronutrient, and heavy metal pollution that may contaminate roadside plants. Adjacent landscape features such as railroads and agriculture provide additional macronutrient and heavy metal...

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1. Verfasser: Emilie Snell-Rood
Format: Dataset
Sprache:eng
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Zusammenfassung:Roadsides are targeted for restoration of pollinator-friendly plants. Yet, roads are sources of macronutrient, micronutrient, and heavy metal pollution that may contaminate roadside plants. Adjacent landscape features such as railroads and agriculture provide additional macronutrient and heavy metal pollution that may exacerbate traffic effects. However, we lack perspective on how roads combine with rural landscape features to influence nutrition of roadside plants, which could have implications for pollinator health. We surveyed roadsides across Minnesota USA and measured foliar levels of dietary macronutrients (nitrogen, phosphorous, and potassium), a micronutrient (sodium), and metals (iron, zinc, copper, chromium, nickel, lead, aluminum, and cadmium) in six abundant roadside forb species used by insect pollinators: Asclepias syriaca, Dalea purpurea, Monarda fistulosa, Ratibida pinnata, Solidago spp., and Trifolium pratense. We aimed to determine (1) how road variables (traffic volume and distance from road) combine with adjacent land use (railroad and agriculture) to influence element content of roadside forbs and (2) whether some forb species show consistent differences in their accumulation of potentially toxic heavy metals, which could inform selection of species to plant along roadsides. We found that foliar concentrations of nine elements increased with greater traffic volume (nitrogen, phosphorous, iron, zinc, copper, chromium, nickel, lead, and aluminum), and concentrations of six elements declined with distance from the road (nitrogen, phosphorous, potassium, iron, zinc, and copper). Leaves collected adjacent to railroad had less phosphorous, potassium, iron, nickel, and aluminum than leaves collected from sites not adjacent to railroad. Additionally, leaves collected from sites adjacent to agriculture had lower copper levels than leaves from sites without adjacent agriculture. We found no evidence that forb species along roadsides consistently rank higher than other species in their accumulation of heavy metals. Our results show that traffic alters more elements in roadside plants than does adjacent landscape context, alleviating concerns that landscape features exacerbate pollutant levels in roadside pollinator habitat. However, nutrient contamination of most roadside plants is unlikely to reach toxic levels for insect pollinators. This work is consistent with the positive conservation potential of low to moderate traffic roadsides for pollin
DOI:10.17632/vmc6znh66m.1