Im Spiegel des Klimawandels – Phosphor und Stickstoff in Böden Schleswig-Holsteins bei steigenden Lufttemperaturen

Background, aim, and scope The ecological effects of the global climate change differ regionally. Due to the ecological significance of soils in terrestrial ecosystems the aim of this study on behalf of the State Agency for Nature and Environment of Schleswig-Holstein was to calculate the output of nitrogen and phosphate from soils in Schleswig-Holstein (Germany) given the current and predicted air temperatures. Methods The calculations were performed by the Water and Substance Modelling System (WASMOD). This complex simulation tool can be used for modelling the fluxes of water and dissolved substances through single soil columns or for fields and watersheds. In this study the calculations rely on data collected from several sources such as agricultural statistics, the German Weather Service DWD, results from the high resolution regional climate model REMO as well as from the German soil inventory “Reichsbodenschätzung”. The WASMOD calculations were performed for representative combinations of ecological characteristics such as soil texture, distance to the ground water table, drainage, cultivation, and climate. The computations refer to three periods: 1975 to 2004 according to the measurements of two meteorological stations (DWD), and in terms of REMO modelling 1971 to 2000 (reference), and 2071 to 2100 according to the IPCC scenarios B1 and A1B. Results The WASMOD results encompass precipitation, interception, evaporation, seepage water, drainage, nitrogen balances (input, mineralisation, denitrification, nitrification, output, volatilisation, and drainage), and phosphate balances (input, mineralisation, output, and percentage of organic, sorbed, dissolved and immobile P). According to the combinations of influencing factors the computed results vary spatially: Given the scenarios B1 and A1B the evaporation is expected to increase. Compared to the reference period the B1 seepage will be high and associated with high precipitation. Nevertheless, due to increasing evaporation A1B is similar to the reference period despite higher precipitation. The B1 scenario showed the highest outputs of N and P. The results for A1B were found to be very similar with those for the reference period. The N output from fields significantly increase in B1. The highest outputs were estimated for intensively grazed feedlots. For B1 the highest P outputs were computed whereas the A1B estimations were lower than the results referring to the reference period. In terms of the input/output ratio the N output from sandy soils will be higher than those from loamy soils while the contrary holds true for the absolute discharge. These findings will vary spatially with the distance of the soil surface from the groundwater table. The expected output by denitrification is negligible whereas from loamy soils such N losses can account for 41?kg/ha. The mineralisation was expected at maximum in A1B. Compared with the reference period B1 will have higher air temperatures and more precipitation but less droughts. Consequently, for these sites reduced mineralisation was estimated. Draining will reduce the N and P output from fields and enhance the P discharge from grassland, respectively. Discussion The WASMOD modelling results could not be compared to findings of similar studies because such could not be investigated. Thus, the discussion had to focus on the data and methods used for the computations, and the results could not be validated empirically. Nevertheless, from many case studies, ecosystem research and environmental monitoring projects which have been published during the last 20 years the computations of this investigation could be classified as, at least, plausible. A major challenge of further investigations will be the regionalisation if the WASMOD results by the combination of high resolution soil data with such on plant phenology. Conclusions Basic research as for instance long-term ecosystem research should be regarded as essential precondition for the development of prognostic models as presented by the example of WASMOD. Such research could be proved as worthwhile in face of problems as represented in this study. Regarding the global change related risk of vector-associated diseases the predictive power of ecological models must be broadened and refined. Recommendations and perspectives Ecosystem research and environmental epidemiology should be coordinated much closer. This research must be attended by a professional documentation of research and monitoring results by use of metadata-based and GIS-based networking of local databases. The approach of the investigation presented should be applied to representative ecoregions of Germany. To reach this, modelling areas will be selected in terms of an ecological land classification and extensive data sets from meteorological and phenological monitoring networks. Additionally, the approach will be extended by the predictive mapping of vector-associated diseases.