SOIL-SOLUTION CHEMISTRY IN A LOW-ELEVATION SPRUCE-FIR ECOSYSTEM, HOWLAND, MAINE

Soil solutions were collected monthly by tension and zero-tension lysi meters in a low-elevation red spruce stand in east-central Maine from May 1987 through December 1992. Soil solutions collected by Oa tension lysimeters had higher concentrations of most constituents than the Oa zero-tension lysimeters. In Oa horizon soil solutions growing season concentrations for SO4, Ca, and Mg averaged 57, 43, and 30 mu mol L(-1 ) in tension lysimeters, and 43, 28, and 19 mu mol L(-1) in zero-tensi on lysimeters, respectively. Because tension lysimeters remove water h eld by the soil at tensions up to 10 kPa, solutions are assumed to hav e more time to react with the soil compared to freely draining solutio ns collected by zero-tension lysimeters. Solutions collected in the Bs horizon by both types of collectors were similar which was attributed to the frequency of time periods when the water table was above the B s lysimeters. Concentrations of SO4 and NO3 at this site were lower th an concentrations reported for most other eastern U.S. spruce-fir site s, but base cation concentrations fell in the same range. Aluminum con centrations in this study were also lower than reported for other site s in the eastern U.S. and Ca/Al ratios did not suggest inhibition of C a uptake by roots. Concentrations of SO4, Ca, K, and Cl decreased sign ificantly in both the Oa and Bs horizons over the 56-month sampling pe riod, which could reflect decreasing deposition rates for sulfur and b ase cations, climatic influences, or natural variation. A longer recor d of measured fluxes will be needed to adequately define temporal tren ds in solution chemistry and their causes.