C accumulation in boreal peatlands has been a result of a relatively small disproportion of production and decay. High water levels and consequent anoxia are considered the major causes for the disproportion. As such, the C sink of a peatland is labile, and sensitive to variations in environmental conditions. Changes in peatland ecosystem functions may be mediated through land-use change, and/or climatic warming. In both cases, drawdown of the water level is a key factor. An extended lowering of the water level induces several changes in a peatland ecosystem. When the vegetation adapts to the new moisture conditions, litter quality may change drastically. With the changing substrate (litter) quality and environmental conditions, the soil microbial community is also like to change. All these factors will have their effects on decay rates of organic matter. In this poster will present results of variation of the initial chemical composition of different litters in pristine and drained peatlands. The aim is to detect, how plant communities in boreal peatlands respond to changing hydrological conditions. This information is needed for modelling of climate change/land-use change impacts on processes determining the C balance of these ecosystems.