Tobias Conradt

Integrated assessment of cropland soil carbon sensitivity to recent and future climate in the Elbe River basin

Abstract Carbon storage in soils is sensitive to changing climatic conditions, potentially increasing C fluxes from soils to the atmosphere. This study provides an assessment of recent climate variability (1951–2000) and potential future (2001–2055) climate change impacts on soil C storage for croplands in the German part of the Elbe River basin. Results indicate that recently (1991–2000) croplands are a net source of carbon (net annual flux of 10.8 g C m−2 year−1 to the atmosphere). The recent temperature trend for the years 1951–2000 (+0.8 K in summer and +1.4 K in winter mean temperature) alone have already caused a significant net flux of 1.8 g C m−2 year−1 to the atmosphere. Future climate change (2001–2055) derived from regionalised meteorological properties driven by the IPCC-SRES A1 scenario results in an increased net C flux of an additional 4 g C m−2 year−1 in comparison to the reference period (1951–2000). Uncertainties attached to C flux results are estimated with a standard error of 6%. Besides climate-induced alteration of net C fluxes, considerable impacts on groundwater recharge (–45.7%), river flow (–43.2%) and crop yield (–11% to −15% as a basin-wide average for different cereals) were obtained. Recent past and expected temperature changes within the Elbe basin predominantly contribute to the increase of net C fluxes to the atmosphere. However, decreased crop growth (crop yields) and decreased expected water availability counteract even higher net C losses as soil C turnover is reduced through less C input (less crop growth) and drier soil conditions (decrease in water availability). Based on this study, present-day and potential future development of net C fluxes, water components and crop yields were quantified. This allows integrated assessment of different ecosystem services (C storage, water availability and crop yield) under climate change in river basins.

Potential impacts of climate change and regional anthropogenic activities in Central European mesoscale catchments.

Abstract The Soil and Water Integrated Model (SWIM) was used to assess potential climate and land-use change impacts in the Central European catchments of Schwarze Elster, Spree and Lusatian Neisse which are heavily influenced by opencast lignite mining. To account for potential climate change, scenarios of two statistical regional climate models, STAR and WettReg, were used. Regional anthropogenic change was considered in terms of increasing cultivation of energy crops (oilseed rape, silage maize, sunflower and sorghum) and decreasing mining activities (decreasing groundwater depression cone). In the climate scenarios, decreased natural discharge, by up to 60% in the long-term average, was simulated. In simulations with climate scenarios and oilseed rape, this effect is halved; the other energy crops have a small additional impact on discharge. The decreasing groundwater depression cone slightly compensates for climate change impacts. Overall, potential impacts of regional anthropogenic activities are secondary to those of climate change. Editor Z.W. Kundzewicz; Guest editor M. White

Measured effects of new lake surfaces on regional precipitation

Abstract Although often modelled, empirical evidence for regional water balance shifts, due to local land-use changes, is rare. The same holds for the quantification of such effects by measurement. The flooding of former open-cast mining areas in Lusatia, eastern Germany, delivers a unique opportunity to address this topic in a well-gauged region. During two decades, flooding changed about 60 km2 of lignite pits to lake surfaces. To quantify possible shifts in the regional precipitation pattern, the background of general precipitation dynamics within the research area was separated from all raingauge records using principal component analysis (PCA). Linear models with the dominating PCA component as independent variable were fitted to the single station records. The residuals of these fits represent the local deviations from the general dynamics, and they contain the signals of climate alterations within the region. The analysis of these residuals revealed a shifting precipitation pattern with significant increases (up to 10% of the former mean annual precipitation, which is approximately 650 mm) on the lee side of the developing lake area. Further analysis showed that most of the observed changes are due to more frequent and intense convective storms. Water balance estimations indicate that the additional evaporation approximately equals the precipitation increase.