Influence of chronic ozone stress on carbon translocation pattern into rhizosphere microbial communities of beech trees (Fagus sylvatica L.) during a growing season

The influence of long-term chronic ozone exposure on carbon fluxes from young beech trees (Fagus sylvatica L.) into the phospholipid fraction of microbial communities (PLFA) in the rhizosphere and into the dissolved organic carbon (DOC) fraction was studied in a lysimeter experiment using (13)C depleted CO(2) over one vegetation period to identify possible changes in below ground carbon translocation processes due to the plant stress. It could be shown that microbial biomass as well as individual microbial communities and their activity pattern in the rhizosphere of young beech trees are mainly driven by the vegetation period. An increase in total microbial biomass as well as individual microbial communities was detected during the vegetation period from June to September. However, also a clear ozone effect was visible mainly at the end of the vegetation period. Enzyme activities and PLFA data indicated earlier induced plant senescence as a response to the elevated ozone treatment. Furthermore higher microbial biomass and abundance of plant C utilizing microbes was observed in elevated ozone treatments over the whole vegetation period.