MICA - Microbial and carbon dynamics in cut-away peatlands cultivated with reed canary grass

Principal investigator: Assoc. Prof. Christina Biasi

Funding period: 2007-2009 Maj and Tor Nessling Foundation

While natural peatlands are CO2 sinks, peatlands drained for agriculture and peat-harvesting areas have been suggested to be persistent sources of atmospheric CO2. Since CO2 is the most important greenhouse gas, it contributes significantly to climate warming which is one of the most serious problems linked to anthropogenic activities and future of the globe. One of the strategies to reduce CO2 emissions is to increase the use of renewable energy. In Finland, cultivation of reed canary grass (Phalaris arundinacea L.; RCG) as a bioenergy and/or fibre crop is increasing rapidly. The grass has proven to give high yield of above-ground biomass for bioenergy (mean 6000 - 8 000 kg dry weight ha-1 yr-1). However, the benefits gained through high yields may be lost, if the huge amounts of carbon from the old peat are mobilized by soil microbes. Microbes are the most important mediators in soil carbon cycling, since they mobilize but also immobilize carbon.

The objective of this study is to assess microbial dynamics linked to carbon cycling in peat soils (cut-away peatland) cultivated with reed canary grass. We aim at understanding carbon flow within the soil by determining effects of cultivation on microbial biomass and activity and elucidating underlying mechanisms. Microbial and carbon dynamics are studied at four different levels:

  1. Microbial activity

Approach: Analysis of CO2 emissions, experiments on carbon mineralization, radiocarbon dating of CO2, stable isotopic methods, determination of net and gross nitrogen mineralization

  1. Microbial biomass and community structure

Approach: PLFA (phospho-lipid fatty acids) analysis, CFE (chloroform-fumigation-extraction)

  1. Decomposition processes and functional roles of microbes

Approach: 13C labelling studies, analysis of soil organic pools, 13C-PLFA assays, litter bag incubations

  1. Extracellular enzyme activities

Approach: Enzyme assayes