Early-warning system for ecosystem changes
Carbon, oxygen, hydrogen and nitrogen – these four crucial elements for life and their compounds are processed by plants, animals and microorganisms and are spread via air and water. The Max Planck Institute for Biogeochemistry studies these global material cycles and the biological, chemical and physical processes associated with them. The scientists in Jena aim to reach a better understanding of the complex interaction of organisms in and on the soil, of greenhouse gases in the atmosphere, of human influence on these processes, and the ways in which ecosystems react to the different challenges they face, such as changes in the climate and species diversity.
The Molecular Biogeochemistry Research Group led by Gerd Gleixner identifies key processes in the global biogeochemical material cycles and studies these processes at molecular level with a view to understanding the changes in ecosystems and identifying them at an early stage. This helps to take measures in good time, ensuring 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 Earth" – Earth's vulnerable skin in which rock, soil, water, air and living plants, animals and microorganisms interact. Interactions taking place in this zone have a major impact on the carbon cycle and, as a result influence climate change and life-conserving ecosystem functions, like food production and water quality.
Dissolved organic matter (DOM) in water is particularly suited to the study of these processes, as these mobile substances can be transported between different parts of the system. 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. 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 organic compounds. The first step to achieving this involves examination of a systematic set of environmental parameters and ecosystem types.
What the molecular fingerprint reveals
Previous findings show that pH value and temperature are important influencing factors on the molecular fingerprint. However, it appears that vegetation composition also has a considerable influence on the composition of DOM. Major changes can be observed in the molecular fingerprint of the upper 60 centimeters of mineral soil. Findings indicate that a fresh plant signal rapidly disappears on entering the soil and a microbially-influenced signal exists. Therefore, it is conceivable that 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 vegetation from that of pH value and site. This requires comparison of the molecular fingerprints of different types of vegetation grown in the same soil conditions, on the one hand, and comparison of the molecular fingerprints of the same vegetation grown at different sites, on the other. To characterize the fresh plant signal in 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 Foundation, 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 estate is particularly suited to the long-term studies needed for the project, and site comparisons can be carried out on the estate, as the prevailing acid conditions in the sandy soil offer an ideal and necessary complement to existing study sites. The grassland vegetation complements existing study sites as concerns to vegetation and pH/site parameters, and it also enables direct comparison of the influence of vegetation (oaks vs. pines vs. grassland) in the case of comparable soil conditions. 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.