Temperature increase accelerates nitrate release from high-elevation red spruce soils

Abstract

One possible consequence of predicted increases in global temperature is an increase in soil organic matter decomposition rates and (or) nitrification rates. In nitrogen-saturated ecosystems, such a change could lead to an increase in nitrate production, since much of the ammonium released from decomposition of organic matter would be converted to nitrate rather than taken up by plants or microorganisms. In a high-elevation red spruce (Picearubens Sarg.) stand, soil at 15 cm below the surface of the sunny and shaded sides of a recent clearing were found to exhibit a significant temperature differential (Δ = 1.2 °C, p < 0.01). Soil solutions collected at 15 cm from the warmer, sunny side over an 18-month period had higher (p < 0.01) mean concentrations of nitrate (71% greater), Mg (58% greater), and Al (24% greater) than those from the shaded side. Fluxes of nitrate and Mg were 30–33% higher on the sunny side of the clearing (p = 0.10, p < 0.01, respectively). If global climate changes result in accelerated releases of nitrate that are widespread in high-elevation spruce–fir forests, elevated Al levels and (or) base cation leaching losses may result, with possible negative consequences for forest health.