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Biogeochemical processes in terrestrial ecosystems: New methodological perspectives to trace organic matter cycling and transformation in soils, sediments and the liquid phase
Convener: Boris Jansen  | Co-Conveners: Nicasio T Jiménez-Morillo , Guido Wiesenberg , Ingrid Kögel-Knabner , Cornelia Rumpel , Luis Parras-Alcántara , Marco A. Jiménez-González 
 / Wed, 15 Apr, 13:30–15:00
 / Attendance Wed, 15 Apr, 17:30–19:00

Soil organic matter transformations related to climate and/or land-use change: a molecular perspective
Soils store more carbon as Soil Organic Matter (SOM) than the atmosphere and standing vegetation combined. Most if not all of this carbon is part of the short-term carbon cycle in the time frame of millennia at maximum. This makes the link with climate change very obvious. It also demands understanding the influence of the (feedback of) climate and land-use change on SOM transformations. As a result, the last decades have seen a vast body of research devoted to tracing and, ultimately, quantifying this relationship by the help of molecular approaches solely or in combination with compound-specific isotopes like 2H, 13C, 15N, 18O. Examples include:
• assessing the role of inherent resistance to decomposition related to molecular SOM structure versus external factors such as protection in aggregates or binding to minerals
• tracing vegetation changes related to natural succession and disturbance as well as anthropogenic management
• unravelling the influence of SOM derived from roots and its potential difference between the fate of SOM derived from aboveground input.
• examining the effects of (variations in) belowground biodiversity, both macro faunal and microbial.
• attempting to link processes working on the molecular scale to large scale levels
The molecular perspective plays a crucial role in such endeavors and has led to a vast and expanding number of molecular proxies applied to study the relationship between SOM tranformations, climate and land-use change. These include, but are not limited to, plant derived extractable lipids and macromolecules such as lignin, cutin and suberin; as well as microbial indicators such as GDGTs and PLFAs. Exciting developments include an increasing drive to derive quantitative information about transformation and pools using manipulative experiments on the one hand and investigation of natural archives on the other hand.
In our session we hope to bring together scientists working in different areas of SOM research, ranging from those specialized in developing new molecular proxies; those primarily focusing on assessing the effects of climate and/or land-use changes on SOM transformations in different settings; to those attempting to upscale effects from the molecular to larger scales. Thus stimulating a cross-fertilization between different areas of expertise all needed to tackle this important issue.

Public information: This session is endorsed by the European Association of Geochemistry (EAG) and the Soil Chemistry Commission of the International Union of Soil Sciences (IUSS).