Plants have the ability to select & store metals derived from the growth substrate and distribute them to tissues. This ability is being used in biogeochemical exploration. This report describes a study to improve biogeochemical techniques applied to mineral exploration by: assessing site-specific criteria with potential to seriously affect metal uptake; and determining optimum sampling criteria for biogeochemical exploration based on tree morphology & sampling site characteristics. The study was designed to address problems associated with seasonal changes, tree morphology, and site quality. Researchers sampled crowns & outer bark from 100 black spruce trees at three different sites near Jenpeg, Manitoba, and measured water flux in trees to distinguish between seasonal metal flux attributable to changes in tree physiology and geochemical flux induced by differences in root water uptake. Results are presented which discuss correlations between element content in samples and root water uptake.