WOULD INCREASE IN UV-B RADIATION AFFECT METHANE RELEASE FROM NORTHERN PEATLANDS? Pertti Martikainen, Department of Environmental Sciences, University of KuopioQUEST Workshop, University of Bristol, June 14-16, 2004

There are data e.g. on the effects - of changing hydrology on carbon gas dynamics - of change in temperature on methane release - of increase in atmospheric CO2 concentration on carbon gas dynamics - of atmospheric nitrogen and sulphate load on methane dynamics

The effects of increase in UV-B radiation on methane (and CO2) dynamics in northern peatlands are unknown - the boreal and subarctic regions (60 -90 oN) will be subjected to a 14 % maximum increase in the annual UV dose in 2010- 20 relative to 1979 – 1992 (Taalas et al. 2000) - - the ozone depletion is most severe during spring, increase in UV dose would be 90 % from the level in 1979-1992.

The increase in UV radiation is a potential stress factor for the peatland vegetation, andthen also carbon dynamics driven by plants and their photosynthesis. There is a link between the primary production and methanogenesis

Effects of global change and anthropogenic activities on carbon gas dynamics

EXPERIMENTS WITH MICROCOSMS

In 1999

Intact peat cores with vegetation from lawn microsites of a minero-

genic, oligotrophic low-sedge S. Papillosum pine fen, Eastern

Finland

Effects of UV treatment on methane emissions from peatlands

Global Change Biology 8: 361-371 (2002)

Effects of ambient, UV-A control and UV-B treatment on methaneemissions from peatland microcosms during the growing season 1999

- Intact peat cores (dia 10 cm, depth 40 cm) with vegetation from lawn microsites of a minerogenic, oligotrophic low-sedge S. Papillosum pine fen, Eastern Finland

- Treatment by UV-B (constant 30 % above the ambient UV-B level) was done at an open-field exposure facility in Kuopio, Central Finland

* UV-B treatment lowered the CH4

emission by 30 % * Decrease in photosynthesis (all plants were included to the measurements * Changes in plant physiology and morphology - increase in membrane leakage of S. angustifolium by UV-B - UV-B reduced the amount of aerenchymatous tissue of Eriophorum vaginatum

(320 – 400 nm) (280 -320 nm)

Sodankylä experimental site in Northern Finland, exposure started in summer 2003Mesotrophic flark fen (close to Sodankylä Geophysical Observatory) -10 control plots-10 plots treated with UV-A-10 plots treated with UV-B (continuously 30 % above the ambient)

Collar in an experimental plot allowing gas-tight connection of chambers for CO2 and CH4 exchange studies

PhD Sanna Saarnio showshow the CO2 dynamics is measured using thermostated chamber and IR analyzer. NEE, respiration and photosynthesis can be measured, and using environmental data (e.g. radiation, temperature, WT) the seasonal CO2 balance can be determined (modelled).

PhD student Sami Mörsky inaction measuring methanefluxes with a static chambermethod. Gas samples are taken Into gas tight vials to be analyzed later In laboratory for CH4 using a gas chromatograph equipped with an autosampler.

After exposure of the first summerThere was no significant differenceIn the carbon gas fluxes. It is knownthat the damages in vegetation canrequire longer radiation stress. Theexperiment will be continued at leastfor two additional years including gasflux measurements during all seasons. Possible changes in plantmorphology/ physiology and soilprocesses/chemistry are also studied.