Atmospheric input of some cations and anions to forest ecosystems in North Carolina and Tennessee

The atmospheric contributions of elements in precipitation and dry fallout to forest ecosystems were measured at two sites in the southern Appalachians. At both sites, relative mean annual concentrations of cations in bulk precipitation were in the order Ca > Na > K > Mg. At the Coweeta Hydrologic Laboratory in North Carolina, average annual inputs of Ca ++ , Na + , K + , Mg ++ , and NH 4 ‐N in 1970–1973 were 4.88, 3.52, 1.62, 1.01, and 0.52 kg/ha/yr, respectively. At Walker Branch, Tennessee, the inputs of these elements during the same time period were 15.73, 3.89, 2.99, 2.94, and 2.37 kg/ha/yr. The inputs Of NO 3 ‐N, PO 4 ‐P, and Cl − in 1972–1973 were 2.88, 0.19, and 8.53 kg/ha/yr at Coweeta. Inputs of NO 3 ‐N and PO 4 ‐P were 4.61 and 0.55 kg/ha at Walker Branch over the same period. One reason for differences in bulk precipitation chemistry was greater dry fallout for some cations at Walker Branch than at Coweeta. For both sites, dry fallout associated with local land use activities influenced seasonal concentrations of bulk precipitation except for Na + , which appeared to be partly derived from marine sources. Total inputs of elements are considered to be minimum estimates for both forest ecosystems due to sampling and analytical methods.