Tree species effects on coupled cycles of carbon, nitrogen, and acidity in mineral soils at a common garden experiment

Forest biogeochemical cycles are shaped by effects of dominant tree species on soils, but the underlying mechanisms are not well understood. We investigated effects of temperate tree species on interactions among carbon (C), nitrogen (N), and acidity in mineral soils from an experiment with replicated monocultures of 14 tree species. To identify how trees affected these soil properties, we evaluated correlations among species-level characteristics (e.g. nutrient concentrations in leaf litter, wood, and roots), stand-level properties (e.g. nutrient fluxes through leaf litterfall, nutrient pools in stemwood), and components of soil C, N, and cation cycles. Total extractable acidity (aciditytot) was correlated positively with mineral soil C stocks (R = 0.72, P \ 0.001), such that a nearly two-fold increase in aciditytot was associated with a more than two-fold increase of organic C. We attribute this correlation to effects of tree species on soil acidification and subsequent mineral weathering reactions, which make hydrolyzing cations available for stabilization of soil organic matter. The effects of tree species on soil acidity were better understood by measuring multiple components of soil acidity, including pH, the abundance of hydrolyzing cations in soil solutions and on cation exchange sites, and aciditytot. Soil pH and aciditytot were correlated with proton-producing components of the soil N cycle (e.g. nitrification), which were Electronic supplementary material The online version of this article (doi:10.1007/s10533-011-9695-7) contains supplementary material, which is available to authorized users. K. E. Mueller (&) D. M. Eissenstat Intercollege Program in Ecology and Department of Horticulture, Pennsylvania State University, University Park, State College, PA 16802, USA e-mail: [email protected] S. E. Hobbie Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN 55108, USA J. Oleksyn A. M. Jagodzinski Institute of Dendrology, Polish Academy of Sciences, 62-035 Kornik, Poland A. M. Jagodzinski Department of Forest Protection, Poznan University of Life Sciences, Poznan, Poland P. B. Reich Department of Forest Resources, University of Minnesota, Saint Paul, MN 55108, USA O. A. Chadwick Department of Geography, University of California-Santa Barbara, Santa Barbara, CA 93106, USA J. Chorover Department of Soil, Water and Environmental Science, University of Arizona, Tucson, AZ 85721, USA