In the northern hemisphere, variability in hydrological conditions was suggested to increase as a consequence of climate warming, which may result in longer droughts than the area has experienced before. Due to their predominately anoxic conditions, peatlands are expected to respond to changes in hydrological conditions, such as successive drying and rewetting periods. As peatlands are rich in organic matter, any major changes in water table may influence the decomposition of it. The hydrological conditions may also influence release of nutrients from peat profiles as well as affect their transport to downstream ecosystems. In our mesocosm experiment, artificial water table fluctuations in pristine peat profiles caused an increase in dissolved organic nitrogen (DON) and ammonium(NH4+-N)concentrations, while no response was found in drained peat profiles, although originating from the same peatland complex.

Hydrological conditions are considered to be among the main drivers influencing the export of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems, and hydrology is likely to alter due to climate change. We built a mesocosm experiment by using peat profiles from a pristine and from a drained (drained in 1978) peatland. A several-week-long low water table period followed by a high water table period, that is, a setting mimicking drought followed by flood, released relatively more DOC from pristine peat than from drained peat. From pristine peat profiles DOC was released into soil water in such quantities that the concentration of DOC remained stable despite dilution caused by added spring water to the mesocosms. In drained peat the DOC concentrations decreased during the high water table period indicating stronger dilution effect in comparison to pristine peat. At the landscape level DOC load from a drained peatland to the recipient water body may, however, increase during flooding because of high water runoff out of the peatland containing high DOC concentrations relative to the forest and agricultural areas. During the high water table period neither peat type nor water table had any clear impact on carbon dioxide (CO2-C) fluxes.

No-till is considered an advantageous agricultural practice for the environment because soil erosion is decreased compared to ploughed soil. However, for an overall evaluation of the benefits and disadvantages of this crop production method, it is also important to understand the soil nutrient cycling in no-till fields. Little is known about how the gross rates of the different processes of nitrogen (N) cycle are affected by tillage practices in agroecosystems in a northern cold climate. Our study was designed to obtain information about gross soil N process rates in boreal no-till and moldboard ploughed spring barley fields after autumn harvesting. Gross organic N mineralization into ammonium (NH4 +) and NH4 + immobilization were the most important N transformation processes in the soil and their rates were higher in no-till soil than in ploughed soil. Regardless of the higher mineralization rate, the gross rate of NH4 + oxidation into nitrate (NO3 −) was clearly lower in no-till soil. This was explained by higher NH4 + immobilization in no-till soil. The lower NH4 + oxidation rate in no-till soil d e c r e a s e d t h e r i s k f o r N O 3 − leaching, which supports the promulgated environmental benefits of this practice.