Influence of bedrock and soil properties on elemental composition of conifers in boreal zone

The plant ionome reflects an interplay between biological requirements and environmental sources, including soil, bedrock, groundwater, and atmospheric dust, as well as factors controlling the bioavailability. Understanding the sources and processes that shape plant ionome is essential for a range of applications, including environmental monitoring, geological mapping, and mineral exploration. The boreal region presents a scenario where the prevalence of allochthonous glacial sediments decouples soil geochemistry from its bedrock source, complicating geological mapping. We investigated the influence of geological and environmental characteristics on the ionomes of Norway spruce, Scots pine, and common juniper in the boreal zone. Samples included bark, twigs, and needles collected from 93 sampling stations across a northern boreal mature forest. Compositional statistical analysis revealed significant effects of edaphic and bedrock properties on conifer ionomes, though responses varied by species and tissue type. Soil moisture and organic matter content strongly influenced cobalt, molybdenum, barium, manganese, but also lead, rubidium, strontium and nickel concentrations. Bedrock geology influenced cobalt, nickel, calcium, magnesium, copper, and lead, detectable even beneath the till cover. A primary challenge lies in determining the specific source for elements originating from both soil and bedrock or mainly one of the sources. Notably, gold‑cobalt mineralisation signals were preserved in Norway spruce bark despite the overlying sediments. These findings demonstrate the utility of conifer ionomes for geological mapping despite complex surficial geology.