Forest Floor Composition in Aspen-and Spruce-Dominated Stands of the Boreal Mixedwood Forest.

The ability of high-resolution cross-polarization magic-angle spinning 13C nuclear magnetic resonance spectroscopy (CPMAS 13C NMR) to characterize soil organic matter (SOM) has been previously demonstrated, but rarely has this information been directly related to local environmental conditions that affect SOM formation. In this study, CPMAS 13C NMR was used to characterize the forest floor (Oe + Oa horizon) of stands dominated by trembling aspen (Populns tremuloides Michx.) or white spruce [Picea glauca (Moench) Voss] in the boreal mixed-wood forest of Alberta, Canada. Aromatic C content was higher and carbonyl C content was lower in the forest floor of spruce stands than in aspen stands. Within stand types, correlation analyses indicated significant relationships between the composition of the forest floor and soil temperature, mass of the Oi horizon, and mass of the moss layer. However, these relationships could not explain observed differences in the chemical composition of the forest floor between stand types. Although forest floor from spruce stands was largely composed of moss, which is low in aromatic C, it had a greater aromatic C content than forest floor from aspen stands, where moss was rare. Furthermore, a lack of significant correlations across stand types suggests that there are different relationships between the chemical and environmental characteristics of forest floor from spruce and aspen stands. [ABSTRACT FROM AUTHOR]