Boreal soil carbon: the stable, the labile, and the unknown

点击翻译按钮获取中文摘要

Boreal forest soils are the single largest terrestrial carbon storehouse in the world. Consequently, changes in boreal carbon stocks and fluxes could significantly affect the global carbon cycle. These northern, high-latitude soils are also highly susceptible to global warming, and in the coming century are expected to face large increases in average temperatures, altered freeze-thaw patterns, and transformative vegetation shifts. The carbon contained in boreal soils is a complex network of interconnected pools whose stability may be controlled by different mechanisms. As such, it has been challenging to predict the response of boreal soil carbon to environmental changes. My long-term research objective is to quantify how the underlying environmental factors control organic matter accumulation and distribution in soils. With this proposed research program, I plan to clarify how interactions between the soil geological material and vegetation may ultimately determine the response of boreal soil carbon to climatic changes. I will address this challenge by:1. Quantifying the sources, formation pathways, and stability of two carbon pools (subsurface and forest floor) that turn over on a decadal time scale; 2. Investigating how carbon fluxes through labile (biological and rhizosphere) carbon pools may be altered by environmental changes, and how this may affect subsequent carbon accumulation pathways and stability.I will be training three PhD and two Msc students, as well as several undergraduate research assistants. Student projects will be independent yet interlinked. The focus of these projects is to understand how various environmental factors, including overall warming, changes in freeze-thaw cycles, and vegetation shifts, will affect the following four boreal carbon stores: 1. Subsurface soil carbon-- We will investigate how soil geological material may control the source and stability of carbon present at depth;2. Forest floor carbon-- We will focus on the carbon present within the deeper, humified organic matter layer, and investigate the possibility that this carbon may, in some cases, be more stable than deep mineral carbon;3. Biological carbon-- We will look at how vegetation changes affect carbon fluxes through soil biological communities in representative boreal forests;4. Rhizosphere carbon-- We will examine how the rhizosphere (zone of root influence) affects the partitioning of microbial carbon fluxes between catabolic and anabolic processes.A variety of boreal forests from across Canada will be included in this program. This will allow for characterization of soil organic matter from wide ranges of geological materials, forest stand types, and climate. The program will combine a sound pedological field approach, isotope labelling experiments in controlled-environment chambers, and state-of-the-art analytical protocols. The result will be an unprecedented characterization of organic matter transformation pathways, which will fundamentally advance our understanding of carbon accumulation and stability in boreal soils. Overall, this research program will establish the foundational scientific knowledge required to improve prediction of boreal soil carbon response to climate change. This will, in turn, inform management and adaptation strategies that are tailor-made for sustaining boreal forest ecosystems.