Spatial patterns in elemental concentrations of the forest floor across the north central USA

Forest floor material was sampled in 171 forest stands, representing five forest types, across the states of Minnesota, Wisconsin, and Michigan. Elemental concentrations of forest floor material were related to forest type, and for most elements, concentrations were also related to location defined by five sampling zones along a north-west-southeast geographic gradient. Calcium, Mg, K, Na, and P decreased in concentration from west to east; Pb and Cd increased; Cu and Zn did not differ among zones, and although Ni differed, there was no pattern to those differences. The trends are consistent with atmospheric deposition of Ca, Mg, K, Na, and P from westerly soil-derived sources and deposition of Pb and Cd from eastern anthropogenic sources.