The role of microbes in soil organic carbon accumulation as a natural climate solution

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Forests are important to Canada both economically and environmentally. One benefit is the ability of forests to store carbon, a component of CO2 an important greenhouse gas (GHG) responsible for climate change. More carbon is stored in forests than is found in the atmosphere, with most of the carbon stored as soil organic carbon (SOC; a mixture of semi-decomposed plant material and microbial biomass). This ability to store carbon has led to many tree planting projects on formerly forested land throughout the world. The Canadian Government has pledged to plant 2 billion trees and promote improved forest management practices to achieve net-zero GHG emissions by 2050. It is thought that tree restoration could act as a Natural Climate Solution (NCS) helping to limit global warming. But there are many important knowledge gaps before forest soils can be counted towards emission targets. Critically, past land-use (e.g. agricultural) can leave lasting legacies on soil, that influence its ability to store carbon. Forests are also under increasing pressure from environmental change and are susceptible to abrupt and intense climate extremes, such as drought, that are expected to increase in frequency and intensity. It is not known how this will impact tree restoration projects and managed forests. Soil microbes play a key role in regulating the amount of SOC but are susceptible to environmental change. SOC content is a balance between microbial decomposition and stabilisation of carbon incorporated into microbial biomass. This balance can shift, with environmental change potentially resulting in stored SOC being released to the atmosphere, further accelerating climate change. We know little about what factors (e.g., past land-use) make soil microbes vulnerable to climate extremes. This is an important knowledge gap. This Discovery Grant will fund three student-led research themes. 1) We will determine the microbial response to tree restoration and their contribution to SOC stocks. This project will use tree restoration projects in British Columbia (BC) and explore how practices can be improved. 2) We will examine the long-term impact of forest management on SOC, using trials established in the early 1990s in BC. 3) We will examine whether forest management and historical land-use allow microorganisms to withstand climate extremes, and how this affects SOC stocks. This project will simulate environmental change in the field across sites in BC and in the laboratory. These three themes will generate new insights and reduce uncertainties of the effects of past land-use and environmental change on SOC dynamics following tree restoration and forest management. This proposed research aligns with the BC government's Forest Carbon Initiative and Canada's net-zero GHG emissions target by 2050 to have maximum policy relevance, and will provide evidence-based results for new tree restoration/forest management policies as a NCS in BC and across Canada.