Our group studies the budgets, fluxes and processes of carbon (C) and nitrogen (N) within boreal ecosystems. We use a multitude of measurement techniques to quantify the pools of C and N in the soil, the microbial processes behind the C and N cycling within the soil, and the fluxes of C and N and trace gases (CO2, CH4, N2O, NOx, VOCs, VONs) between the soil and the atmosphere. We also work with process-based modeling of C and N cycling within the soil and the whole ecosystem. Most of our field measurements are conducted at the SMEAR II .research station in Hyytiälä.

kulo

Reactive trace gas exchange between boreal soils and the atmosphere

Soils are identified as sources of several trace gases, such as N2O, CH4, CO2, VOCs and VONs, which have a strong role in the climate change, in air quality issues and in tropospheric chemistry. We have intensively studied the formation processes and exchange of these gases in the soils of the different boreal ecosystems by continuous measurements and measurement campaigns. For the detailed understanding of the processes related to the exchange of these gases, we have also conducted several laboratory experiments with controlled conditions. The impacts of forest management practices on soil trace gas exchange we have studied with four-year forest clear-cut/prescribed burning experiment. In addition to measurements conducted in boreal ecosystems, we have measured N2O emissions from the intensively managed cotton field in south-eastern China. For the measuring of trace gases, we apply several micrometeorological methods from manual and automatic chamber measurements to soil gas profile modeling and eddy covariance. In order to improve the quality of chamber measurements, we organized a calibration campaign at Hyytiälä forestry field station in 2008 to compare chambers with a range of volumes and diameters used for N2O, CH4 and CO2 emission measurements.

Projects

  • Exchange of volatile organic compounds in boreal forest floor
  • Effect of prescribed burning and clear-cut to soil greenhouse gas balance
  • Exchange of Greenhouse Gases between Ecosystems and Atmosphere . Field Measurements and Modelling (EGGBEAM)
  • Nitrogen fixation of boreal forest
  • Development of static chamber measurement techniques and assessing the uncertainty
kammio

Processes underlying trace gas emissions from soils

Nitrogen and carbon are cycled in the soil by microbial processes which are tightly connected to above ground environment, to trees, understory vegetation, and to the atmosphere. To understand the interactions between below and above ground, and changes in the soil nitrogen and carbon pools, we study functioning of microbes, microbial usage of nitrogen and carbon pools in the soil, and mycorrhizal connection between soil environment and vegetation. Nitrogen and carbon compounds are altered in the soil; they are released in the soil or taken up into the soil by microbial processes. These processes are driving force to trace gas exchange between the soil and the atmosphere, and they are keystones in carbon-nitrogen dynamics between the above ground biosphere and soil microbial communities. We study these microbial processes by using field measurements and laboratory experiments. Our main focus is on field site at SMEARII and laboratory facilities are located in Viikki-campus in Helsinki.

Projects

  • FASTCARBON
  • Girdling experiment
sienet

GHG fluxes and balances of boreal ecosystems

We study the inputs, outputs and storage changes of carbon, nitrogen, water and other compounds to boreal forest ecosystems. Carbon is assimilated by photosynthesis, and released in respiration. Our focus is in understanding the origin of soil CO2 flux and stability of the soil carbon storage. We are studying what is the role of recent photosynthates on the decomposition of old soil organic matter and its connection to the nitrogen acquisition of vegetation. Gas exchange measurements, modelling, stable isotopes 13C and 15N and radioactive isotopes are our key tools in understanding the processes underlying soil organic matter decomposition.Low nitrogen availability limits tree growth in boreal region. The main inputs of nitrogen to the ecosystem are atmospheric deposition and nitrogen fixation. Because of antropogenic emissions, in europe, the input of nitrogen to the ecosystems is several times higher than in pre-industrial times. We are studying how the increased nitrogen deposition affects nitrogen availability in the forests, as well as harmful N2O and NOx emissions to the atmosphere. In addition to nitrogen, the budgets of key nutrients, such as P, K, Ca and Mg are under investigation.

NBALANCE

The most important storages and fluxes of nitrogen in a boreal Scots Pine forest. Green arrows indicate inputs of nitrogen to the ecosystem, orange indicate internal cycling of nitrogen in the ecosystem, and red arrows indicate nitrogen outputs from the ecosystem. In mineralization part of the large organic nitrogen pool in soil is transformed into inorganic nitrogen, which is very active and alters many processes.

muurahainen