Project duration: 1.1.2015-31.12.2017

Funding: Nessling foundation

Partners: Finnish Meteorological Institute (FMI, coordinator), University of Helsinki (UHEL), Natural Resources Institute Finland (LUKE)

Project description:

Drainage of peatlands for forestry has been a common practice in northern Europe. In Finland, about 20% of all forests grow on drained peatlands, one-third of these growing on nutrient-rich peat. After the drainage, particularly the nutrient-rich sites show large carbon losses into the atmosphere and to water. One option to reduce the adverse environmental impacts of peatland forestry is to moderately increase the ground water level, which should eventually lead to smaller carbon dioxide (CO2) and dissolved organic carbon (DOC) emissions, however at the same time not to enhance methane (CH4) emissions.

In this project the effect of a moderate water level increase on C balance of a forestry-drained peatland is studied at the Lettosuo site, Tammela, southern Finland. A partial harvest, removing the pine trees which compose 75% of the total wood biomass, was conducted in March 2016. Following the harvest, the water level has increased 15-20 cm, which was expected due to the decreased transpiration of trees. At the clear-cut area, established at the same time, a much more radical water-level increase was measured.

In this project we will compare the 5-years long forest CO2 flux and evaporation data, soil GHG flux data, as well as the leaching of C, collected prior the harvest, to that measured after it. We have established smaller control and clear-cut experimental areas within the larger area with partial harvest. At each of these three treatments we will measure greenhouse gas (CO2, CH4, N2O) fluxes with manual and automatic chambers, and DOC fluxes by manual and automatic sampling at  measurement weirs.

Specific research questions:

1. What is the impact of WL rise on the peat and litter decomposition rate and tree growth?

2. How are the GHG balances altered following the harvest and ground water level rise?

3. What is the impact of harvest on the water balance and DOC leaching?

The overarching aim is to test, whether the adverse environmental impacts of a nutrient-rich forestry-drained peatland can be reduced by means of raising the ground water level

Map of the Lettosuo site

News about the project:

• December 2017: The project is ending. Eddy covariance measurements and Letto1 autochambers will continue, others will be gradually taken to other sites.

• September 2017: An extended abstract by Mika Korkiakoski in the Center of Excellence Annual meeting presenting first results from the clear-cut eddy covariance measurements

• August 29-31, 2017: 1st ICOS Nordic meeting  in Copenhagen. Oral presentation about the project results by Mika Korkiakoski.

• July 2017: An LGR N2O/CO analyzer of UHEL installed at the automatic chambers of Letto2 control. Now we can directly compare results from Gasmet (CO2, N2O, CH4), LGR (N2O) and Picarro (CO2/CH4)

• May 2017: Two eager summer trainees started working at the site, taking care of the system and collecting data from manual chambers, ditches and wells etc. 

• May 2017: New Gasmet instrument was installed at the automatic chambers of Letto2 control site. Will be used for manual chamber measurements, too!

• April 2017: First paper out! "Methane exchange at the peatland forest floor – automatic chamber system exposes the dynamics of small fluxes" by Mika Korkiakoski.

• December 22, 2016 Last extension collars installed to automatic chambers. Welcome, snow!

• Summer 2016 Researchers from the Department of Physics (Univ. Helsinki) have been collecting samples of tree CH4 emission and soil concentrations.

• June 6, 2016 19 automatic water table level loggers installed to existing manual sampling points at the site.

• April 18, 2016 Two abstracts and poster presentations about CH4 fluxes and carbon balance before logging presented at EGU general assembly in Vienna, Austria.

• April 7, 2016 Eddy covariance measurements of CO2/H2O fluxes started at the clearcut area.

• March 16, 2016 The logging at the site has finished!

• February **29, 2016** The logging at Lettosuo has started and will continue for the next two weeks.

• October 26-27, 2015 Two abstracts and one poster presentation about the results of CH4 fluxes measured at Lettosuo in 2011-2013 presented at ICOS 4th annual Greenhouse Gases, Science and Society conference in Helsinki, Finland.

• September 22-24, 2015 An extended abstract written about the results of CH4 fluxes measured at Lettosuo in 2011-2013 to Annual Center of Excellence seminar held in Kuopio, Finland.

• July 24, 2015 Started meteorological measurements at Letto3 site.

• July 12, 2015 Started automatic CH4 flux measurements at Letto2 site.

• June 12, 2015 Started meteorological and automatic CO2 flux measurements at Letto2 site.

• June 4, 2015 Started automatic N2O and CO flux measurements at Letto1 site