Tree recovery following disturbance in the boreal forest

我们将研究影响加拿大西部北方森林颤杨和白云杉补充的基质、播种和更新环境。首先，我们将加深对演替阶段的理解，包括林分组成和干扰前的密度以及干扰类型对树木更新环境的影响。我们将使用干扰前的遥感和干扰后的遥感和地面采样相结合的方法来确定每个系统的演变轨迹。再远一点。我们将使用类似的技术来评估经过密集管理的北方针叶林的恢复情况，这些森林已经转变为纯净的针叶林，然后再次受到火灾的干扰。由于这些森林的许多遗留元素已经被除草剂的使用所消除，它们的自然演替发展模式将因缺乏萌芽繁殖和存在侵略性的草而受到阻碍。第三个研究领域将研究杨树种子的再生--允许杨树随着气候变化进入更高的海拔和纬度。白杨种子的丝状毛发使它可以随风移动很远的距离，即使在它着陆后，它也会继续在地面上移动，直到它停留在最后的微型站点上。通过田间试验和实验室试验，我们将研究杨树种子在种子落地后，在不同水分和质地的微站点上的再利用情况，以便更准确地评估种子在良好微站点上停留的可能性。第四，在以针叶树为主的北方针叶林中，羽毛苔藓占主导地位。这些苔藓既没有吸水的根，也没有控制水分损失的气孔，因此它们在降雨后会迅速干涸，但它们会影响氮素循环、树木补充和生态系统进程。通过田间观察和试验，我们将评估这些干湿循环与羽毛苔藓活力、基质孔隙度、水力传导性和氮素有效性的关系。这项工作适用于这一重要基质的苗木建立和火灾风险建模。四名学生将接受培训。

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.