WOULD INCREASE IN UV-B RADIATION AFFECT METHANE RELEASE FROM NORTHERN PEATLANDS?

1. WOULD INCREASE IN UV-B RADIATION AFFECT METHANE RELEASE FROM NORTHERN PEATLANDS? Pertti Martikainen, Department of Environmental Sciences, University of Kuopio QUEST Workshop, University of Bristol, June 14-16, 2004 Effects of global change and anthropogenic activities on carbon gas dynamics 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, and then also carbon dynamics driven by plants and their photosynthesis. There is a link between the primary production and methanogenesis

2. 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 Effectsof UV treatment on methane emissions from peatlands

3. Effects of ambient, UV-A control and UV-B treatment on methane emissions 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 (320 – 400 nm) (280 -320 nm) * 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 Global Change Biology 8: 361-371 (2002)

4. Sodankylä experimental site in Northern Finland, • exposure started in summer 2003 • Mesotrophic 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)

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

6. PhD Sanna Saarnio shows how 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).

7. PhD student Sami Mörsky in action measuring methane fluxes with a static chamber method. 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 summer There was no significant difference In the carbon gas fluxes. It is known that the damages in vegetation can require longer radiation stress. The experiment will be continued at least for two additional years including gas flux measurements during all seasons. Possible changes in plant morphology/ physiology and soil processes/chemistry are also studied.