Podzolisation and soil organic matter dynamics

Present models of podzolisation emphasize the mobilization and precipitation of dissolved organic matter, together with Al(-silicates) and Fe. Such models cannot explain the dominance of pellet-like organic matter in most boreal podzols and in well-drained podzols outside the boreal zone, and the discrepancy between the chemistry of percolating organic matter (DOC) and the organic matter accumulated in well-drained podzol-B horizons. The present paper offers an amended podzolisation theory, in which relative contribution of illuviated organic matter and root litter together with organic matter dynamics provide an explanation for the large variation in podzol morphology. It is suggested that fast organic matter dynamics as occurs on nutrient-rich parent materials in the boreal zone causes small accumulation of organic matter, mainly derived from roots. In such soils, the colors of Fe components dominate in the B horizon. Slow organic matter dynamics, as occurs on nutrient-poor parent materials and under hydromorphic circumstances, favors large organic matter accumulations in the B horizon, and a larger abundance of DOC-derived organic matter coatings. The latter group includes tropical podzols.