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增收的基质、种子和更新环境。首先，我们将完善我们对演替阶段（包括干扰前的林分组成和密度）和干扰类型如何影响树木更新环境的理解。我们将使用干扰前的遥感和干扰后的远程和地面采样的组合来确定每个系统的连续轨迹。进一步。我们将使用类似的技术来评估密集管理的北方针叶林的恢复情况，这些针叶林已经转变为纯针叶林，然后被火灾重新扰乱。由于这些森林的许多遗留元素已被除草剂清除，它们的自然演替模式将因缺乏发芽繁殖体和侵略性草的存在而受到阻碍。第三个研究领域将检查白杨从种子的再生——允许白杨在气候变化的情况下迁移到更高的海拔和纬度。白杨种子的丝状绒毛使它能够随风移动很远的距离，即使在落地后，它也会继续在地面上移动，直到它停在最后的微点上。通过田间和室内实验，我们将研究杨树种子在不同湿度和质地的微位点上的附着情况，以便更准确地评估种子在良好微位点上停留的概率。④针叶林林下以羽苔为主。这些苔藓既没有根来吸收水分，也没有气孔来控制水分的流失，因此它们在降雨后迅速枯干，但它们影响氮循环、树木补充和生态系统过程。通过田间观察和实验，我们将评估这些干湿循环与羽苔活力、基质孔隙度、水力导率和氮有效性的关系。工作适用于这种重要基质的幼苗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.