Origin and fate of organic matter in sandy soils along a primary vegetation succession

Until now little is known about the role vegetation plays in the organic matter formation, particularly at the molecular level. Most ecosystems have a long history, which is unknown or too complex to find distinct relations between vegetation and the chemical composition of soil organic matter. To gain a better insight in such relationships, the relative simple soil-vegetation system of the Hulshorster Sands and Leuvenum Forest is used. The complete vegetation succession has been investigated, making it possible to monitor the organic matter development. During the succession, thus with time, the pH decreases, the ectorganic layer becomes thicker and the soil develops towards a micro-podzol.Chapter 2 describes the organic matter composition and relation to the first stages of vegetation development in the pre-podzol phase. In the Ah horizon under grass ( Corynephorus canescens ), the organic matter has virtually no contribution of the covering vegetation. Algae, from an earlier stage, and mosses ( Polytrichum piliferum and Bryum sp.), from adjacent spots, are the main suppliers. Under mosses, the organic matter is very similar to that of the original species. An aliphatic biopolymer, derived from mosses, that produces a series of branched alkene/alkane doublets (C 20 -C 32 ) together with a homologous series of n -alkenes and n -alkanes (C 10 up to C 34 ) upon pyrolysis, appears to be very recalcitrant in the first stages of succession.In the vegetation stages following mosses, these aliphatic macromolecules are still an important source of the aliphatic part of organic matter. Apart from the aliphatic moss contribution, the organic matter under Callunavulgaris and Pinus sylvestris has a close relationship with the contributing plant parts: flowers, leaves and branches dominate the organic layer under Calluna , needles predominate the ectorganic horizon under pines, and the soil organic matter in the Ah horizons in both cases is almost completely determined by roots