A positive correlation between soil metal content and plant metal accumulation has been used by biogeochemists to assist mineral exploration in areas of minimal outcrop. Much-needed study of the impact of vegetation sample collection over an extended time-frame, impact of site drainage, as well as the choice of vegetation sample type are presented. Evaluation of seasonal variability, together with measurements of tree water flow-rate (affected by weather conditions) on tree crown metal uptake was also undertaken to ascertain whether this variability could mask the geochemical signatures or whether normalization to weather conditions is needed. Thirty-three elements, including Au, Ag, Ni, Co, Zn and Cu, were studied. Other factors such as tree crown, outer bark and tree appearance were also studied. Black spruce was selected due to its ubiquitous presence in the boreal forest of central Manitoba. The best agreement between the crown twig metal accumulation and tree water uptake was identified for the rare earth elements (REEs) and the essential elements (Ca, K, Mg, Fe, P, Zn), which also exhibited the highest seasonal variation. The content of pH-sensitive elements (Ag, Co, Ni, Rb, Mn, Cu) in black spruce crowns did not display any direct relationship to the tree water uptake. Elements most affected by site drainage conditions include Ag, Co, Ni, Rb, Mn and Cu. These metals were found in substantially larger quantities in crowns of trees growing on well drained sites. Gold concentrations in outer bark samples growing on well drained sites were 12 times lower than the same samples collected from poorly drained sites. Au, Pb, W, Th, Na, Al were found in substantially larger concentrations in thin (up to 4 mm in diameter) compared to thicker twigs. Ag and Ca accumulated preferentially in thick twigs. K, Mg, P, Mn, Zn, Cu, Au, Ag, Rb and W were present in substantially higher concentrations in the crown twigs compared to outer bark. Pb, B, Hf, Th, V and REEs were present in the outer bark at eight to ten times higher concentrations than in crown twigs, and Hf, Na, Sb, Sc and V five times higher. W was not detectable in the outer bark but its content in the twigs was well above the detection limit. Crown morphology, the outer bark appearance and the number of tree transpiring branches had no measurable effect on metal contents in the assessed tree organs.

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