Doctoral Dissertation

23.11.2018: The primary constraint in peat decomposition and C cycling could be reversed under global climate change (Mpamah)


23.11.2018 12:00 — 15:00

Location: Muu , University of Eastern Finland, Kuopio Campus
Release: 23.11.2018: The primary constraint in peat decomposition and C cycling could be reversed under global climate change (Mpamah)
Changing climatic conditions can alter microbial biomass and community composition, increase microbial activities and trigger decomposition of the organic matter in the deeper peat layers by changing microbial processes and indirectly by affecting substrate availability.

Peatlands are globally the most efficient terrestrial carbon reservoirs storing one third of the terrestrial carbon. In Finland, peat is the most important long-term carbon store with carbon amounts exceeding that stored in vegetation and mineral soils. However, as a dynamic ecosystem, peatlands have the capacity for a huge feedback to the climate by affecting balance of carbon dioxide in atmosphere through the sequestration or emissions of carbon.

Peat carbon storage processes may change

Peat efficiency as an atmospheric carbon sink and long-term carbon storage is affected by the rate of microbial mineralization, which vary due to hydrology affecting the balance between aerobic and anaerobic degradation as well as the nutrients status and temperature. Thus, the surface peat carbon store is labile and sensitive to changes in climate and land use, which is affecting their hydrology and temperature. Peat in deeper layers is considered more recalcitrant and less sensitive to environmental changes than the younger surface peat. This doctoral dissertation by Promise A. Mpamah from University of Jyväskylä (Finland) compared microbial biomass, microbial community composition and carbon cycling processes in drained vs. natural peat profiles with the focus on deep old peat.

- My study indicated that the carbon retained by living and dead microorganisms in peatlands might contribute substantially more to the carbon storage of peatlands at regional scales than originally thought, says Mpamah.

The study further showed that there were living microorganisms in all the peat layers, including the bottom layers that are over 3000 years old. Microorganisms in the old and deeper peat layers are smaller in abundance and slower in action than the microorganisms in the younger surface peat layers. The main reason for old peat recalcitrance compared to the younger peat is the lower abundance and activity of microorganisms. Results from over 40 year drained peatlands in Finland showed that drying of peatland surface changed the abundance and composition of microorganisms in all the studied depths. Thus, projected increased temperature and drying due to global warming can increase the amount and activity of microorganisms in peat and turn them from long-term carbon store to carbon emitters.

- Peat carbon cycling models should consider the input of microbial biomass carbon. In addition, studies on the carbon dynamics of peatlands in changing climate should not be limited to the surface layers only, tells Mpamah.

M.Sc. Promise Mpamah defends his doctoral dissertation in Aquatic Sciences "Response of microbial biomass and carbon dynamics to changing hydrological conditions in old peat deposits" on the 23rd of November 2018 in University of Eastern Finland (Kuopio Campus). Opponent Professor Ülo Mander (University of Tartu, Estonia) and Custos Professor Marja Tiirola (University of Jyväskylä, Finland). The doctoral dissertation is held in English.

Additional information:

The dissertation is published in the JYU Dissertations series. ISSN 2489-9003; ISBN 978-951-39-7606-4. Link to dissertation:

More information

Promise Mpamah

Bio- ja ympäristötieteiden laitos