Tree recovery following disturbance in the boreal forest

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We will study the substrate, seeding and regeneration environments affecting the recruitment of trembling aspen and white spruce of boreal forests of western Canada. First we will refine our understanding of how successional stage, including stand composition and density before disturbance and type of disturbance affects the regeneration environment for trees. We will use a combination of remote sensing prior to disturbance and remote and ground sampling after disturbance to determine successional trajectories in each system. Further. we will use similar techniques to assess the recovery of intensively managed boreal forests that have been converted to pure conifer forests and then redisturbed by fire. As many of the legacy elements of these forests have been removed by herbicide applications, their natural pattern of successional development will be impeded by lack of sprouting propagules and by the presence of aggressive grasses. A third area of study will examine regeneration of aspen from seed - allowing movement of aspen into higher elevations and latitudes with climate change. The silky hairs of aspen seed allows it to move great distances by wind and even after it lands it will continue to move over the ground surface until it is lodged on its final microsite. Using both field and lab experiments, we will examine the resorting of aspen seed onto microsites of different moisture and texture, after the seed lands, in order to more accurately assess probability of seeds stopping on good microsites. Fourth, feather mosses dominate the understory in conifer-dominated boreal forests. These mosses have neither roots for water uptake nor stomata to control water loss, therefore they undergo rapid dry-down after rainfall, but they influence nitrogen cycling, tree recruitment and ecosystem processes. Using both field observations and experiments, we will assess these wet-dry cycles in relation to feather moss vigor, substrate porosity, hydraulic conductivity and N availability. Work applies to seedling establishment and modelling risk of fire for this important substrate. Four students will be trained.******