Bodenmikrobiologische Untersuchungen an Pseudogleyboden un ter Wald im Sacb sischen Hugelland 1): Soil -microbiological Investigations into Pseudogley Soils under Forest Cover in the Hilly Region of Saxony

Abstract

Summary By the conversion of a mixed hardwood forest suited to the site into pure plantations of spruce the humus form on pseudogley sites in the hills of Saxony changes from a mull-like moder to raw humus. At the same time the hydrogen ion concentration and the C/N ratio in the H and A1 horizons increase. The portion of bacteria and actinomycetes in the microbe population and the cellulose-decomposing ability, proteolysis and nitrification decrease considerably. Repeated fertilization of the spruce stands end this negative development and adapt the microbe population to that of the humus in the original mixed hardwood forest. Thus, thanks to the furtherance of bacteria and actinomycetes the total number of germs increases. The number of species of actinomycetes increases materially, in the case of fungi, however, the number remains constant. Decomposition of cellulose, C02 release, proteolysis, nitrification, and denitrification are considerably furthered, the fertilizer combination CaNP turning out to be particularly favourable. In this combination great importance is attached to phosphorus, single treatment with N gives no effect at all. Thus, P deficiency in the pseudogleys is close related both with the soil-biological activity and, as previous investigations have shown, with stand nutrition. The 9 year fertilization, however, did not cause a change in the humus form hitherto. A change from spruce to more site-adapted and presumptuous tree species with easily decomposable litter and root distribution into greater depths would promote the conversion process in humus. Besides, these species are believed to respond stronger in their growth to the increased microbial activity than spruce.