The Molecular Biogeochemistry Research Group led by Gerd Gleixner identifies key processes in the global biogeochemical material cycles and studies these processes at the molecular level with a view to understanding the changes in ecosystems and identifying them at an early stage. This means that measures can be taken in good time to ensure that important ecosystem functions are conserved in a changing environment. The focus of the Group's research lies in the study of the so-called "critical zone of the Earth" – the Earth's vulnerable skin in which the rock, soil, water, air and living plants, animals and microorganisms interact. The interactions that take place in this zone have a major impact on the carbon cycle and, as a result, also influence climate change and life-conserving ecosystem functions, like food production and water quality.
The dissolved organic matter (DOM) in the water is particularly suited to the study of these processes, as these are mobile substances that can be transported between different parts of the system. The dissolved organic compounds contain an ecosystem’s molecular fingerprint. These "molecular fingerprints" can be read and characterized using state-of-the-art, complex analysis methods, for example electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and nuclear magnetic resonance spectrometry. The aim is to identify new marker substances in the molecular fingerprint of ecosystems, which can help to elucidate these processes already taking place. The focus here is on identifying how strongly certain environmental parameters and the interaction of plants and microorganisms in an ecosystem influence the molecular composition of the organic compounds. The first step to achieving this involves the examination of a systematic set of environmental parameters and ecosystem types.
Previous findings show that the pH value and temperature are important influencing factors on the molecular fingerprint. However, it appears that the vegetation composition also has a considerable influence on the composition of the DOM. Major changes can be observed in the molecular fingerprint of the upper 60cm of mineral soil. The findings indicate that the fresh plant signal rapidly disappears on entering the soil and a microbially-influenced signal exists. Therefore it is conceivable that the cleaning capacity and capability of soils can be described with the help of individual markers.
Based on the results already obtained, the Max Planck Institute for Biogeochemistry is now working on differentiating the influence of the vegetation from those of the pH value and the site. This requires the comparison of the molecular fingerprints of different types of vegetation grown in the same soil conditions, on the one hand, and the comparison of the molecular fingerprints of the same vegetation grown at different sites, on the other. To characterize the fresh plant signal in the soil more accurately, it is necessary to compare the molecular fingerprint of fresh plants with the molecular fingerprints in different stages of decomposition.
The project is supported by the Zwillenberg-Tietz Stiftung, both through funding and infrastructure, as the foundation’s property includes a large estate in the Havelland area, located a one-hour drive west of Berlin. The site is particularly suited to the long-term studies as needed for the project, and the site comparisons can be carried out on the estate site, as the prevailing acid conditions in the sandy soil offer an ideal and necessary complement to the existing study sites. The grassland vegetation complements the existing study sites in relation to the vegetation and pH/site parameters and also enables the direct comparison of the influence of the vegetation (oaks vs. pines vs. grassland) in the case of comparable soil conditions. The DOM measurements from the sites are regularly compared with atmospheric environmental influences, which are measured on-site by a weather station established specifically for the project.
Image: MPI for Biogeochemistry.