Plant effects on the soil community: A microcosm experiment

An experiment was carried out in microcosms for testing the hypothesis that a higher level of primary production should maintain a decomposer community with higher biomass and activity. Microcosms with coniferous forest humus and a diverse microbial and faunal community were divided into three sets: (1) control without plants, (2) with birch seedlings in full illumination, and (3) with birch seedlings, shaded to reduce the net primary production. During 16 weeks of incubation at +16 degrees C, no treatment effects were found in numbers or biomass of taxonomic or functional groups of soil organisms, nor in the system respiration in darkness. The community structure of the shaded systems differed from that of the other two treatments (CCA analysis). High organic content of the soil and long time-lag in the system response were considered the main reasons for the small difference between the treatments. (C) 1999 Editions scientifiques et medicales Elsevier SAS.