MINERALIZATION ACTIVITY OF MICROBIAL BIOM ASS IN RECLAIMED SOILS IN COMPARISON WITH EMPIRICAL MATHEMATICAL-MODEL

This study compared two different approaches for assessing biological potential of reclaimed soils: 1) an empirical mathematical model for t opsoil microbial evaluation comparing measured values with model minim um for microbial biomass carbon (MB-C) and with model maximum for extr acellular extractable organic carbon (EX-C) and 2) actual and laborato ry estimation of microbial parameters associated with mineralization a ctivity of the whole microbial community: respiration rate (RR), gluco se-stimulated potential respiration response (PR), biomass specific re spiration rate (qCO(2)) and capability to utilize easily available org anic substrate. Six different reclaimed dumps from North Bohemian Brow n Coal Basin were selected for that purpose. The selected sites formed a reasonably wide range of possible results of reclamation process. T he soils in the first category (two sites suitable for agronomic manag ement and one extensive meadow) were found to have well developed MB-C (72 to 78% of model minimum) associated with relatively high minerali zation activity. Model findings were fully confirmed by estimation of actual and potential mineralization parameters: relatively low content of EX-C; high ratio PR/PR: 13.8 to 15.2 and relatively high conversio n rate of added glucose-C to biomass-C. The opposite situation was fou nd in the case of technically adjusted dump without a prospect for bio logical reclamation: low MB-C content (22% of model minimum); relative ly high content of EX-C associated with low mineralization activity; e xtremely low potentiation of respiration response by glucose (PR/RR ra tio 3.2). Both compared experimental approaches were able to detect po sitive changes in reclaimed dump overlaid with unsuitable loamy loess after application of organic materials (increased MB-C content, increa sed mineralization capacity, lower maintenance energy requirements and higher biosynthesis of MB-C from available organic substrate). Biomas s specific respiration rate was confirmed to be a sensitive indicator of physiological stress both in field and laboratory conditions, parti cularly when evaluated simultaneously with EX-C.