The relationships among microbial parameters and the rate of organic matter mineralization in forest soils, as influenced by forest type

Vegetation type influences the rate of accumulation and mineralization of organic matter in forest soil, mainly through its effect on soil microorganisms. We investigated the relationships among forest types and microbial biomass C (MBC), basal respiration (R-B), substrate-induced respiration (R-s), N mineralization (N-min), specific growth rate mu, microbial eco-physiology and activities of seven hydrolytic enzymes, in samples taken from 25 stands on acidic soils and one stand on limestone, covering typical types of coniferous and deciduous forests in Central Europe. Soils under deciduous trees were less acidic than soils of coniferous forests, which led to increased mineralizing activities R-B and N-min, and a higher proportion of active microbial biomass (R-s/MBC) in the Of horizon. This resulted in more extractable organic C (0.5 M K2SO4) in soils of deciduous forests and a higher accumulation of soil organic matter (SUM) in coniferous forest soil. No effect of forest type on the microbial properties was detected in the Oh horizon and in the 0-10 cm layer. The microbial quotient (MBC/C-org), reflecting the quality of organic matter used for microbial growth, was higher in deciduous forests in all three layers. The metabolic quotient qCO(2) (R-B/MBC) and the specific growth rate mu, estimated using respiration growth curves, did not differ in soils of both forest types. Our results showed that the quality of SOM in coniferous forests supported microorganisms with higher activities of beta-glucosidase, cellobiosidase and beta-xylosidase, which suggested the key importance of fungi in these soils. Processes mediated by bacteria were probably more important in deciduous forest soils with higher activities of arylsulphatase and urease. The results from the stand on limestone showed that pH had a positive effect on microbial biomass and SUM mineralization. (C) 2014 Elsevier GmbH. All rights reserved.