The soil chemical environment along a forest primary successional sequence on the Tanana River floodplain, interior Alaska

Alkaline soils exist under forest vegetation on the Tanana River floodplain of interior Alaska. The objectives of this study were to describe the soil chemical properties and to examine controls on these chemical properties along a forest primary-successional sequence. Soil saturation pastes were prepared from duplicate sites along the successional sequence representing bare alluvium (stage I), open willow (stage III), poplar–alder (stage V), and white spruce (stage VIII). Calcium, Mg, SO4, and ions responsible for alkalinity were the dominant solutes in the saturation extracts. Soil horizons were generally calcareous (CaCO3) and therefore alkaline (pH > 7.0) across the successional sequence. The CaCO3-containing soil horizons were saturated to supersaturated with respect to calcite. Many soil horizons in the plots of stages III and V from one site were saturated with respect to gypsum (CaSO4•2H2O), whereas other stages and sites were generally undersaturated. Phosphate availability in CaCO3-containing so...