INFLUENCE OF AGGREGATE ARCHITECTURE AND MINERALS ON LIVING HABITATS AND SOIL ORGANIC-MATTER

We used an integrated approach to determine the effects of soil partic le architecture and minerals on living habitats and soil organic matte r (SOM). Macroaggregate (> 250 mu m), microaggregate 1 (50-250 mu m), and microaggregate 2 (< 50 mu m) fractions of adjacent forested and cu ltivated Gleysolic soil were obtained by wet sieving. The forested sit e was used as a reference to evaluate the effects of cultivation on so il particle architecture. Aggregates and respective clay fractions wer e characterized using optical, chemical, physical and microbial method s. Microaggregates 1 had primary particles with the largest mean equiv alent spherical diameter (ESD) and void volume of all aggregate fracti ons. These physical characteristics were paralleled by the highest SOM and microbial biomass content, and number of microorganisms. Cultivat ion increased the weathering of primary particles and SOM loss, and de creased the content of microbial pools, suggesting deteriorated living habitats. Soil organic C content in aggregates correlated significant ly with the amount of ammonium oxalate extractable Al, chloritized ver miculite, and vermiculite, and was inversely associated with the total clay content. The mean ESD of primary particles and expandable phyllo silicates of aggregates influenced living habitats by supplying substr ates, and providing different void and protective space for soil micro organisms.