TY - Generic T1 - Elevated CO2 and O3 alter soil nitrogen transformations beneath trembling aspen, paper birch, and sugar maple. Y1 - 2006 A1 - Holmes, W.E. A1 - Zak, D.R. A1 - Pregitzer, K.S. A1 - King, J.S. JF - Ecosystems VL - 9 ER -