Influence of coniferous and deciduous vegetation on major and trace metals in forests of northern New England, USA

Climate change and land-use are predicted to shift coniferous stands to deciduous stands in northern New England. This change in vegetation type may modify plant-soil cycling of major and trace metals, potentially affecting soil fertility and contaminant transport. We studied eight pairs of adjacent coniferous- and deciduous-dominated forest stands across northern New England, USA. We estimated the mean residence time (MRT) of each metal in organic horizons using calculated litterfall from allometric equations and interpolated atmospheric deposition rates. Coniferous stands had 30-50 % smaller organic horizons pools of Ca, K, Mg, Mn, and Zn than deciduous stands. Mineral horizon metal pools were similar between vegetation types. Foliar metal concentrations and pools were smaller at coniferous stands than deciduous stands. The organic horizon MRT for Ca, Cd, Cu, K, Mg, and Mn was predicted to be 40-200 % longer for coniferous stands than deciduous stands. Based upon our findings, we conclude that a shift from coniferous to deciduous vegetation could decrease the accumulation and retention of major metals in the organic horizons. Further investigations into the effect of vegetation type on mineral horizons are needed to constrain regional changes.