Decline of red spruce in the northern Appalachians: assessing the possible role of acid deposition

High-elevation spruce-fir forests of the eastern US receive particularly high rates of acidic deposition (up to 4 keq of H/sup +//ha/yr), vegetation is exposed to highly acidic cloud moisture for up to 2000 h/yr, and very high levels of trace metals have accumulated. Red spruce (Picea rubens) in the northern Appalachians have died in abnormally large numbers over the past two decades without obvious cause. Considerable attention has been focused on the possible role of acid deposition in the decline. Several plausible mechanisms have been offered by a variety of researchers, but to confirm any of these mechanisms requires additional research. 31 references, 6 figures, 1 table.