Effect of soil warming and rainfall patterns on soil N cycling in Northern Europe

With climate change northern Europe is expected to experience extreme increase in air temperatures, particularly during the winter months, influencing soil temperatures in these regions. Climate change is also projected to influence the rainfall amount, and its inter- and intra-annual variability. These changes may affect soil moisture regimes, soil water drainage, soil nitrogen (N) availability and N leaching to aquatic environment and N2O emissions to atmosphere. Thus it is important to study the effects of increased soil temperature and varying rainfall patterns on soil N cycling in arable land from temperate climates, which is a major source of N pollution. An open-field lysimeter study was carried out during 2008–2009 in Denmark on loamy sand soil (Typic Hapludult) with three factors: number of rainy days, rainfall amount and soil warming. Number of rainy days included the mean monthly rainy days for 1961–1990 as ‘normal’ and half the number of rainy days of former as ‘reduced’ treatments. Rainfall amount included mean monthly rainfall for 1961–1990 as ‘present’ and the projected change in mean monthly rainfall for 2071–2100 as ‘future’ treatments. Soil warming included increase in soil temperature by 5 °C at 0.1 m depth as ‘heated’ and non-heated as ‘control’ treatments. Automated mobile rain-out shelter and irrigation system, and insulated buried heating cables were used to impose the treatments.