STUDENT ABSTRACTS - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 278

Can UV-B alter the carbon gas (CO 2 , CH 4 ) dynamics of peatland ecosystems?
RIIKKA NIEMI 1 , PERTTI J. MARTIKAINEN 2 , JOUKO SILVOLA 3 , ANU WULFF 1 ,
TOINI HOLOPAINEN 1
1 Department of Ecology and Environmental Science, University of Kuopio, Kuopio,
Finland
2 Department of Environmental Sciences, University of Kuopio, Kuopio, Finland
3 Department of Biology, University of Joensuu, Joensuu, Finland
Northern peatlands have major atmospheric importance. Since the last glacial
period, they have accumulated 455 Pg carbon in the peat deposits. Besides sinks for
CO 2 , peatlands are one of the most important sources of CH 4 1 . The importance of plants
that possess gas conducting aerenchymatous tissue for CH 4 emission is well
documented 2 . Peatlands cover large areas in Siberia, Scandinavia and the northern North
America. Although great increases in UV-B are being predicted for this region, there is
no published data on the UV effects on peatland carbon dynamics so far.
To evaluate whether UV could alter the peatland carbon gas dynamics, we
exposed peatland microcosms to modulated supplemental (30%) UV radiation at an
open field facility in Kuopio, Central Finland (62q13cN, 27q35cE) in two 3-month-long
experiments. The microcosms were intact peat monoliths (depth 40 cm, 11 cm) with a
continuous Sphagnum moss matrix and some aerenchymatous plants (mainly
Eriophorum vaginatum ) and dwarf shrubs.
At the end of the first experiment, CH 4 emission was 30% lower from the UV-B
treated monoliths than from the monoliths receiving only ambient radiation 3 . Gross
photosynthesis and net CO 2 exchange were significantly lower in the UV-B treatment
than in the UV-A control. The changes were most probably associated with the UV-B
induced morphological changes in E. vaginatum i.e. reduced leaf cross section (-25%)
and percentage of the aerenchyma (-14%). In the second experiment, we observed no
clear UV effects on the carbon gas dynamics. The disparity between the experiments
may be explained by different UV doses: during the first experiment, the weather was
mostly warm and sunny, while during the second experiment it was cool and cloudy.
There is a great need for future research in this complex area.
References
1. Bartlett KB, Harriss RC (1993) Review and assessment of methane emissions from wetlands, Chemosphere
26: 261-320.
2. Schimel JP (1995) Plant transport and methane production as controls on methane flux from arctic wet
meadow tundra, Biogeochemistry 28: 183-200.
3. Niemi R, Martikainen PJ, Silvola J, Wulff A, Turtola S, Holopainen T (2002) Elevated UV-B radiation
alters fluxes of methane and carbon dioxide in peatland microcosms, Global Change Biology , 8: 361-371