Interaction between microbial biomass and activity and the soil chemical conditions and the processes of acid load in coniferous forest soils

Abstract

The primary aims of the present investigation were to determine the proportion of microbial driven soil processes associated with acidification in coniferous forest soils, and the response of microbial communities with respect to soil acidification and to acidification processes. Lysimeters containing undisturbed soil columns from five forest sites in Europe were installed in a spruce forest in the Solling (northern Germany) and exposed to the same input and climatic conditions. In the present study root uptake was excluded. Under these conditions, during the 21 months of the experiment, acid load by microbial N-transformations especially mineralization and subsequent nitrification were the most important processes ranging from 50.2% to 79.1%. Except for one soil the balances showed, that increasing levels of soil acidity decreased the potential of mineralization. This agreed with the observation that microbial biomass Cmic decreased. The biomass Cmic (kg ha-1 a-1) was significantly correlated to N-output. The caloric quotient qW increased parallel to decreasing pH. During the experiment the pHCaCl2 in all mineral soil horizons decreased significantly. This change in soil chemical conditions did not affect the microbial biomass Cmic but the caloric quotient increased during the experiment, especially in the upper mineral soil. © WILEY-VCH Verlag GmbH, 1998.