Learning about organic decomposition to understand climate

Dead organic matter can be degraded by microorganisms which use it as an energy source and oxidize it to carbon dioxide. But much of the material escapes degradation, and it is unclear why. Lars Tranvik is studying potential causes of the phenomenon, which may ultimately yield insights into processes impacting climate.

Huge quantities of dead organic matter are to be found in soil, peat, and in the sediments and water of lakes and oceans. It often endures because of protection from degradation that has so far been little researched.

Tranvik wants to test a number of hypotheses about factors governing the amount of organic matter that is broken down. These may be the inherent chemical structure of the material, or external factors such as the way it binds to mineral surfaces, and the obstacles preventing decomposing enzymes from reaching the organic matter.

The idea is that the project will result in a model for stability of organic matter that applies to all habitats. It should include how organic matter is protected by attaching to clay particles, for example, how decomposition changes with the age of the material, the importance of diversity – both of the dead organic matter, and of the microorganisms that break it down – and how decomposition is hampered at low concentration. Carbon dioxide is released when organic matter decomposes. Greater knowledge about decomposition of dead organic matter – detritus– would therefore improve our understanding of the carbon cycle as a whole. This applies not least to the exchange of carbon dioxide between the atmosphere and ecosystems, and how this may impact and be impacted by future climate.

Tranvik wants to combine knowledge from several research fields specializing in soil, inland waters and seas. He considers that communication between these fields is currently sub-optimal, with the result that widely differing theories about the stability of organic matter prevail in different quarters.