Changing Climatic Conditions Might Have an Impact on Peatlands’ Carbon Cycle

Continuous changes in climatic conditions can lead to various changes. For instance, they can increase microbial activities, modify microbial biomass and community composition, and activate decomposition of the organic matter in the deeper peat layers by altering the processes of microorganisms and by indirectly impacting the availability of substrates.

Peatlands have the ability to store one-third of the terrestrial carbon, which makes them the most efficient terrestrial carbon reservoirs in the world. In Finland, peat is considered to be the most significant long-term carbon store containing carbon amounts that surpass those stored in mineral soils and vegetation. Conversely, since peatlands are dynamic ecosystems, they possess the capacity for an enormous feedback to the climate by influencing carbon dioxide balance in the atmosphere through carbon emissions or sequestration.

Peat carbon storage processes may change

The rate of microbial mineralization, which differs owing to hydrology that influences the balance between anaerobic and aerobic degradation and also the temperature and nutrients status, impacts the efficiency of peat as an atmospheric carbon sink and long-term carbon storage. Hence, the surface peat carbon store is unstable and sensitive to climate changes and land use, which is impacting their temperature and hydrology.

It is believed that peat in deeper layers is more wayward and less susceptible to changes in the environment when compared to the younger surface peat. This doctoral thesis by Promise A. Mpamah from University of Jyväskylä (Finland) compared carbon cycling processes, microbial community composition, and microbial biomass in natural versus drained peat profiles with focus given to 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.

Promise Mpamah, University of Jyväskylä.

In addition, the study demonstrated that all the peat layers, including the bottommost layers that are more than 3000 years old, contained living microorganisms. When compared to the microorganisms in the younger surface peat layers, those in the deeper and old peat layers are slower in action and smaller in abundance. The lower activity and abundance of microorganisms are the chief reason for the recalcitrance of old peat as opposed to the younger peat.

Results from more than 40-year-drained peatlands in Finland demonstrated that drying of the surface of peatland altered the microorganisms’ composition and abundance in all the analyzed depths. Therefore, the projected elevated temperature and drying as a result of global warming can boost the activity and number of microorganisms present in peat and change them to carbon emitters from long-term carbon store.

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.

Promise Mpamah, University of Jyväskylä.

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