Autor:innen:
Sara L. Bauke | Rheinische Friedrich-Wilhelms-Universität Bonn | Germany
Josephine Iser | Rheinische Friedrich-Wilhelms-Universität Bonn
Heike Schimmel | Rheinische Friedrich-Wilhelms-Universität Bonn
Dymphie J. Burger | Rheinische Friedrich-Wilhelms-Universität Bonn
Prof. Dr. Wulf Amelung | Rheinische Friedrich-Wilhelms-Universität Bonn
Sulfur (S) in soils mainly occurs in organic forms, and its cycling should be primarily controlled by the same factors as those for carbon (C) and nitrogen (N), the other two main constituents of soil organic matter. Here, we aim to test this assumption based on a global meta-analysis of soil organic C, N and S contents. We reviewed existing literature with a focus on grassland soils as one of the major global ecosystems, including both native grasslands and managed grasslands with additional fertilization. Element concentrations and supplementary parameters (mean annual temperature and precipitation, texture, pH, soil group, management) were retrieved from the studies, while C:S and N:S element ratios were either directly obtained from the studies or calculated.
Concentrations of OC, N and S were significantly higher in pastures compared to native grassland, while the average ratios of C:N, C:S and N:S were at similar levels. However, the variation of C:S ratios was higher than for C:N ratios in both land uses. Also, C:N ratios were significantly positively correlated with mean annual precipitation and mean annual temperature, while C:S ratios were significantly negatively correlated with both parameters. We therefore suggest that the generalization of S turnover in soils being analogous to C and N turnover is false. For a better understanding of the underlying processes, we are now taking advantage of soil samples collected from native and managed grassland sites along climatic transects across Europe and North America. These samples will be analyzed for isotope ratios of the respective elements (δ13C, δ15N and δ34S) to obtain detailed insights on S cycling in organic matter turnover in relation to C and N turnover.