SS1.05 How Will Aquatic Ecosystems Respond to Climate Change?
Date: Tuesday, June 11, 2002
Location: Poster Session - VCC
 
LarmolaT, Dept Biology, Univ. Joensuu, Joensuu, Finland, tuula.larmola@joensuu.fi
Alm, J, , Finnish Forest Research Institute, Joensuu Research Centre, Joensuu, Finland, jukka.alm@metla.fi
Juutinen, S, , Dept Biology, Univ. Joensuu, Joensuu, Finland, sari.juutinen@joensuu.fi
Saarnio, S, J, Dept Biology, Univ. Joensuu, Joensuu, Finland, sanna.saarnio@joensuu.fi
Martikainen, P, J, Dept Environmental Sciences, Univ. Kuopio, Kuopio, Finland, pertti.martikainen@uku.fi
Silvola, J, , Dept Biology, Univ. Joensuu, Joensuu, Finland, jouko.silvola@joensuu.fi
 
FLOODS CAUSE LARGE INTER-ANNUAL DIFFERENCES IN THE ECOSYSTEM CO2 EXCHANGE IN BOREAL LAKE-ASSOCIATED WETLANDS
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Ecosystem CO2 exchange was measured along three transects in boreal lake-associated wetlands in Finland during two ice-free periods with contrasting flooding patterns (1998-1999). In order to evaluate effects of the duration of flood on CO2 dynamics along a moisture gradient, seasonal gross photosynthesis, ecosystem respiration and net ecosystem CO2 exchange (NEE) were reconstructed by means of regression models and time series of environmental variables. The changes in water level and vegetation development resulted in large inter-annual differences of 30-70 g CO2-C m-2 in the seasonal NEE in the littoral. A prolonged flood in early summer reduced the respiration and caused a delay in vegetation development. During the wetter season, the upper flooded zones with the highest photosynthetic capacity had net losses up to 89 g CO2-C m-2 as gross photosynthesis was more reduced than respiration. In contrast, prolonged inundation could turn a lower flooded site to a net sink of CO2. As relatively small changes in production or decomposition result in large shifts in NEE, the lake-associated wetlands seem to be sensitive to changing climate.