GROWTH AND ELEMENTAL CONTENT OF 2 TREE SPECIES GROWING ON ABANDONED COAL FLY-ASH BASINS

Differences in aboveground tissue concentrations of trace elements were assessed for sweetgum (Liquidambar styraciflua L.) and sycamore (Platanus occidentalis L.) growing on two abandoned coal fly ash basins and a control soil (Fuquay sand; loamy, siliceous, thermic Arenic Plinthic Kandiudult; pH = 4.99). The "wet basin" (pH = 5.58) had originally received precipitator ash in an ash-water slurry, while the "dry basin" (pH = 8.26) had received both precipitator and bottom ash in dry form. In general, trees from the wet basin exhibited elevated trace element concentrations in comparison to the controls, while the dry basin trees exhibited reduced concentrations. One of the most striking differences in elemental concentrations among the ash basin and control trees was observed for Mn, with the control trees exhibiting concentrations orders of magnitude greater than the ash basin trees. Differences in foliar trace element concentrations among the sites can generally be explained by differences in substrate trace element concentrations and/or substrate pH. While trees from the wet ash basin generally had the highest trace element concentrations, these trees also attained the greatest height and diameter growth, suggesting that the elevated trace element concentrations in the wet basin substrate are not limiting the establishment of these two species. The greater height and diameter growth of the wet basin trees is presumably a result of the greater water-holding capacity of the substrate on this site. Differences in growth and tissue concentrations between sweetgum and sycamore highlight the importance of using more than one species when assessing metal toxicity or deficiency on a given substrate.