Specificity of plant-microbe interactions in forest soils

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Forestry is critical to Canada's economic prosperity, nearly half Canada's landmass is forested and Canada contains 10% of the world's forests. In British Columbia forestry is the key industry, over half the province is forested. In addition, forests are vital for moderating climate and filtering air and water and as places of recreation. There is increasing emphasis on sustainable forest management, balancing resource extraction with retention of ecosystem services and biodiversity. In order to provide a basis for rational decisions forest managers must have sufficient knowledge about how forests function and how their management affects that functioning. Nutrient cycling and uptake have been shown to be critical processes for the health of forest ecosystems. The soil microbial community has a key role in nutrient cycling processes in soil through decomposition of soil organic matter and turnover of inorganic nutrients and minerals and, therefore, forest productivity. Soil microorganisms are also crucial to global climate, being responsible for the production and consumption of greenhouse gases (GHG). Although the importance of the soil microbial community is clearly recognized, we know very little about the diversity of microorganisms in soil, what their functional roles are and what factors influence the size, the structure and the activity of the microbial community. Mycorrhizal (fungus-root) associations are ubiquitous in forests though the reasons why certain tree species such as Douglas-fir can associate with up to 2,000 different fungal species and red alder only 50 remains an enigma. Equally, there is little comprehension of the specificity, seasonality and succession of these fungal associations with tree roots or how the growth pattern of different fungal species through the soil affects spatial variability in nutrient availability, through interactions with other soil microorganisms (e.g. bacteria and archaea). Developing management strategies for forest ecosystems requires an understanding of the processes regulating soil nutrient cycling and the impact of various management practices on these processes. A key to this understanding is an understanding of carbon flow and signals between trees, their mycorrhizal associates and their interactions with free-living microorganisms. Similarly, there is a paucity of information on GHG from natural ecosystems, particularly methane (CH4) and nitrous oxide (N2O), which have 30 and 300 times the global warming potential of CO2, respectively. Our knowledge of GHG fluxes from forest soils are complex, contradictory and essentially unknown because the microbes responsible for emission and consumption of these gases are uncultured and methods for studying these organisms did not exist until recently. This research program will use a variety of novel molecular and biochemical methods coupled with stable isotope labeling and probing approaches to identify the important micro-organisms, their specificity in plant interactions and elucidate their role in soil processes such as nutrient cycling, greenhouse gas fluxes and the storage or release of carbon, and clarify the manner in which they interact with plant roots. This will result in a better understanding of ecosystem functioning. This research will also provide new insight into the regulation of important non-CO2 greenhouse gases at both landscape and microbial levels in the soil. Gaining this new knowledge will provide the basis to make sound assessments of carbon sequestration under global change and develop forest management strategies that can meet future mitigation demands.