Microbial activities in soils of a healthy and a declining reed stand

Microbial processes were investigated in the soil of a declining, more eutr ophic (Rozmberk West) and a healthy looking, less eutrophic (Rozmberk East) freshwater reed stand. Soil was sampled monthly from June to September 199 7. Glucose induced carbon dioxide (CO2) production in oxic and anoxic condi tions, methane (CH4) production, nitrification and denitrification activiti es were measured in laboratory conditions in suspensions prepared from homo genised soil samples. Within a stand the proportion of anaerobic (as oppose d to aerobic) microbial activity was greatest in June. Potential methanogen esis was highest in June and decreased later in both stands. Methane produc tion was approximately the same in June at both stands but it was higher at Rozmberk East than at Rozmberk West stand in later months. Denitrifying ac tivity was higher in August than July at both stands. Nitrifying activity w as undetectable at both stands over the entire study period. Generally Rozm berk West was more anaerobic than Rozmberk East, with lower redox potential , higher amounts of oxygen-consuming organic matter and a lower ratio of CO 2 production in oxic conditions to CO2 production in anoxic conditions. Mic robial activity was apparently restricted at Rozmberk West stand in compari son to Rozmberk East. The shift from aerobic to anaerobic microbial metabol ism and a coinciding restriction of metabolic activities at Rozmberk West a re thought to be indicative of a strengthened oxygen stress in the soil, as sociated with accumulation of metabolites toxic to both the microorganisms and the reed. Possible links between eutrophication, microbial characterist ics and reed performance are discussed.