Working Group Soils in the Climate System

Peatlands and permafrost soils are long-term repositories for great amounts of carbon. Global climate change could lead to a partial release of this carbon into the atmosphere in the form of greenhouse gases. The Research Group “Soils in the Climate System” investigates the role that these carbon-rich landscapes play in the regional and global climate system. How do climate change and changes in land use affect the water and carbon fluxes in these landscapes? Expeditions to the Russian Taiga, the Arctic Lena Delta in Siberia or the undisturbed peatlands of Patagonia provide data from these difficult to access regions, which have hardly been investigated up to now. We combine observations and experiments with hydrological and biogeochemical models in close cooperation with modeling and observation groups within CliSAP/CEN.

Aims

The Research Group contributes to the investigation of the role of peatlands and permafrost landscapes within the climate system and the global carbon cycle by

collecting high-quality data on the land-atmosphere and land-hydrosphere exchange fluxes of water, carbon and nutrients from under-researched peatland and permafrost sites, which are provided to the Earth science community,
optimising ecosystem exchange flux measurement methodology,
analysing the interlinked controls of vertical CH₄, CO₂ and water fluxes and lateral carbon and nutrient fluxes by pedological, hydrological and atmospheric controls,
studying the pronounced spatial heterogeneity of carbon and nutrient dynamics on plot (micro-) and landscape (meso-) scales and its implications for mass balance assessments and up-scaling studies,
contributing to the implementation, parameterisation and validation of wetland and permafrost modules of mechanistic Earth system models, and
developing new statistical methods for model-data intercomparison purposes.

Energy, Water, Carbon and Nutrient Dynamics of Permafrost Landscapes

Arctic Permafrost Landscapes in North-East Siberia

In collaboration with the Research Group of Prof. Dr. Julia Boike from the Alfred-Wegener-Institute in Potsdam we investigate the soil-water-atmosphere system in permafrost landscapes of the Lena River Delta in North-East Siberia. In 2009, we set up a new, state-of-the-art micrometeorological system to determine the land-atmosphere fluxes of energy, water, CO₂ and CH₄ on the Island Samoylov, in the central Lena River Delta (72°N, 126°E) . This system is now one of the best equipped and most recognised land-atmosphere flux observation systems in the Arctic. The investigations were expanded in the following years to include measurements of discharge from the island’s central polygon-covered watershed so that the lateral fluxes of water and carbon can be incorporated into budget studies. Other work in North-East Siberia through the DFG-funded Polygon project has focused on spatial variability in nutrient availability in permafrost soils.

Motivation

Permafrost soils are long-term repositories for globally significant quantities of carbon, nitrogen and other elements, which have accumulated over centuries to millennia due to water-saturated and cold soil conditions. Climate change could lead to pronounced changes of the energy and water budgets of permafrost soils and to a partial release of the stored carbon and nitrogen either into the atmosphere in the form of greenhouse gases or to the aquatic systems by lateral waterborne element exports.

Due to this positive feedback on climate warming, these carbon-rich systems are considered as tipping elements of the climate system. However, predictions of how these landscapes might develop under a changing climate are still highly uncertain, which is due to (i) a scarcity of observational data, especially for the Arctic and Russia, (ii) a still insufficient understanding of the many nonlinearly interlinked soil, vegetation and atmosphere processes working on different spatial and temporal scales, and (iii) the missing representation of permafrost and wetland dynamics in most current Earth system models. We approach these three problems in close cooperation with various modelling and measuring working groups at the UHH and other scientific collaborators.

In the delta of Lena River — Photo: UHH, Institute of Soil Science, Christian Wille

Greenhouse Gas Balance of Degraded Peatlands in Temperate Europe

Rewetted Peat Extraction Site Himmelmoor Near Hamburg

The managed bog 'Himmelmoor' is located 21 km NW of the city of Hamburg. The peatland was used for peat mining for several decades with a strong mechanisation since the last 50 years. Nowadays, the peat mining is still active, but approximately 50 % of the area is now out of usage and will be restored in the coming years. For our project, the change from an intensively mined peatland to a near-pristine ecological system is of high interest. Particularly, we are interested in how and why the exchange of energy, water and trace gases will change in response to the rewetting of the peatland. In 2011, we installed an eddy covariance tower to measure the fluxes of energy, water, carbon dioxide and methane. Additionally, we plan to conduct closed chamber measurements to improve our knowledge on the microscale variability of trace gas fluxes.

Besides our research at the 'Himmelmoor', we use the field site for education of bachelor and master students. Our aim is to educate students in the whole range of ecosystem sciences related to flux measurements. This includes technical training at the different instruments, management of complex datasets and mathematical as well as statistical analyses.

We cooperate closely with LI-COR Biosciences GmbH. As partners, we work together to train students and scientists in the field of eddy covariance methodology.

Measurements in the Himmelmoor — Photo: UHH, Institute of Soil Science, Peter Schreiber