Soil organic matter at the root of solutions for climate change mitigation and adaptation

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Soil organic matter (SOM) plays a crucial role in mitigating and adapting to climate change. Increasing SOM in agricultural soils is one of the most short-term and viable option to augment carbon (C) storage, limit global warming and reach carbon neutrality by 2050. Plant roots contribute substantially to SOM; living roots release exudates, associate with symbiotic microorganisms and enmesh soil particles to form aggregates, and dead roots serve as a major C and nitrogen (N) input into the soil. However, roots could also destabilize SOM by stimulating its decomposition by soil microorganisms. Moreover, global warming will likely affect plants and belowground processes, but effects on C and N cycling in the soil remain unclear. A quantitative assessment of how roots affect the balance between C and N retention and losses in soil is necessary to develop climate-smart soils and agroecosystems and increase SOM and C storage. Still, few data exists on how roots and microorganisms affect belowground processes. The long-term objectives of the proposed program are: (1) characterize root traits of perennial and annual species used in temperate agroecosystems, (2) evaluate how root traits and climate variables affect SOM processes, and (3) identify root traits that increase storage and limit losses of C and N, in topsoil and subsoil of Eastern Canadian clay soils. The proposed program contains two main themes: (A) How living and decomposing roots of different plant species affect SOM and (B) How climate variables and species diversity affect root traits and SOM. It involves laboratory experiments under controlled conditions (Theme A) and field experiments under natural conditions (Theme B). Morphological, chemical, architectural, and biotic characterisation of specific root traits, together with analyses of C, N, 13C and 15N concentrations in density fractions of the soil, will allow tracing root-derived C and N and studying SOM stabilization mechanisms in topsoil (i.e., 0-20 cm depth) and subsoil (i.e., >20 cm depth). Virtually no data exist to asses the influence of grassland and cropping species, functional groups and communities on C and N stabilization in Eastern Canada, nor there is any information on how roots traits impact soil functioning. This original, hypothesis-driven research program will provide new knowledge on some of the most important issues related to climate change mitigation and adaptation. This research program at the cutting edge of functional ecology and soil science will have a strong impact by creating bridges between these areas and filling gaps in our comprehension of the soil-plant system. With this research program, I will form 1 PhD, 2MSc, 3UG students that will help design and manage climate-smart soils and agroecosystems. Funding through a Discovery Grant represents a significant contribution to the huge efforts Canada must make to fulfill the Paris Agreement engagements and achieve carbon neutrality by 2050.