Relationship of Availability of Phosphorus and Cations to Forest Succession and Bog Formation in Interior Alaska

Abstract

Concentrations of P, K. Ca. Mg, Mn, and Zn in black spruce foliage were examined in relation to forest succession on north slopes in interior Alaska. decline in levels of P and K in the foliage appear to be deficient on sphagnum soils. Mg levels show a slight decrease, but do not fall below deficiency status even on deeper sphagnum soils. Ca, Mn, and Zn show no relationship to forest succession and are at adequate levels on all stages. Concentrations of available phosphorus and exchangeable cations in the soils show no differences between soils corresponding to those found in nutrient levels in the foliage. However, total quantities of P, K. and Mg in available and exchangeable forms are consistently lower in sphagnum soils. Also, the depth distribution of these nutrients on a volume basis differs among soils: in sphagnums they are located at deeper depths, while on mineral soils they are concentreted in surface layers. this distribution difference and the incrasing coldness of the soil as moss accumulates appear to be sufficient to reduce the availability of these nutrients. Radiocarbon dates showed that 18—28 inches (41—71 cm) of sphagnum peat, weighing 270,000—510,000 kg/ha, had accumulated in less than 185 years. The average annuual increase of 1,500—2,800 kg/ha indicates that, in spite of low growth of trees on sphagnum soils, total productivity in dry weight is appreciable.