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Bachelorarbeit

Stable carbon isotopic signatures of pedogenic carbonates in Westrussia dependent on morphology and depth

Betreuer: Martina Gocke, Yakov Kuzyakov

The discussion shows, that the results of this study still lead to many conclusions, even though there have been severe problems caused by the sample preparation, which lead to about one third of unreliable measurement results. To begin with, the soil organic matter samples revealed that their δ¹³C values increased with increasing depth, likely because the environment in the sampled subsurface horizons provides more favourable living conditions for microorganisms. Furthermore, a shift in the signatures of soil organic matter from north to south is probably explained by changing vegetation and climatic conditions, but not by a strongly increasing portion of C4 vegetation at the southern sites. In the second place, the measured carbon contents clearly showed the distribution of carbonates in the soil with maximum percentages in Bck and Bkc horizons, respectively. Thirdly, the interpretation of the 13C/12C ratios for pedogenic carbonate led to several insights. The soil type itself probably has a minor influence on the 13C/12C ratio because the results vary a lot in all investigated profiles. Instead of that the measured signatures become lower with increasing depth which can be explained by the decreasing influence of atmospheric CO2 and the expanding impact of soil CO2. The latter has a lower δ¹³C value due to fractionation processes than the first. In addition it cannot clearly be stated whether the different morphologies of pedogenic carbonates lead to a similar signature for some of the results are probably influenced by rests of organic material and for loesskindels as well as pseudomycelia too few reliable data has been available to be able to come to a final conclusion. So it still would be worth to do further research on the δ¹³C signatures of pedogenic carbonates with different morphologies since the question whether the morphology has a significant influence on the 13C/12C ratio could not be answered with the results of this study.

Letzte Änderung 08.11.2010