Boreal Under Pressure- Vegetation Shifts and Soil Carbon Response.

Boreal forests are expected to face large temperature increases over the next century. This will have a significant impact on forest composition and its carbon balance. Northward migration of the entire boreal biome is predicted and, within the main boreal forest, deciduous trees will replace evergreens. Forest composition will also shift to younger stands due to increased fire occurrence. It is therefore critical to evaluate the vulnerability of boreal soil carbon to vegetation shifts, in order to more accurately predict the response of the entire boreal biome to global environmental change.

This presentation will outline the analytical synergy of different approaches to advance the scientific understanding of organic matter processes in boreal forest soils including: solid-state ¹³C NMR spectroscopy, biomarker analysis, and bulk and compound-specific ¹³C isotopic analyses. Macromolecular NMR fingerprinting combined with molecular-level biomarker analysis has allowed for greater precision in the identification of soil carbon sources and the quantification of humification processes in boreal forest floors. Tracking of carbon utilization by microbes is accomplished through stable isotope probing of fatty acids following addition of different ¹³C-labeled substrates including ¹³C-labeled tree litter (leaves and roots). When combined, these analytical approaches best characterize the mechanistic interactions among vegetation, composition of soil microbial communities, and soil carbon stability.