Initial soil structural development under different types of vegetation

In September 2007, undisturbed soil cores were taken from experimental fields in The Netherlands and in Northern Sweden that had been under different types of vegetation during four years. From these cores, thin sections were prepared to study the initial soil structural development, changes in organic matter distribution and soil biological activity in relation to plant species growing on the plots. In the Swedish samples, differences between plots with Poa pratensis and Phleum pratense were striking. The Poa plot showed more filled biological burrows, more rounded soil aggregates and also the amount of fine disperse organic matter seemed higher, whereas under Phleum the individual mineral grains more often showed a thin coating of very fine organic matter. Plots with Trifolium repens showed a slightly less pronounced development when compared to the Poa plots. The plots of Trifolium pratense plots and the mixed plot showed highest amounts of biological activity and soil structural development.
The samples taken from the clay soils from The Netherlands showed similar biological activity under pure Lolium perenne and binary mixtures of L. perenne with the legumes T. repens, T. pratense and Medicago sativa from a trial that was not fertilized with N. A high activity of Lumbricus festi was shown by common excremental pellets in channels. In contrast, under Achillea millefolium in an adjacent N fertilised experiment, this activity was completely absent.