Root identification, dynamics and plasticity of boreal species on reclaimed saline-sodic overburdens and naturally saline sites

油砂地区约有6500公顷的再生景观，其中大部分由覆盖层中含盐量高的材料组成，覆盖层顶部覆盖着厚达1.5 m的泥炭/矿物土壤。这些覆盖层的厚度具有生态影响，因为较厚的覆盖层将最大限度地减少盐从覆盖层迁移到覆盖层对根系的负面影响，但也会减少下游湿地的水量。此外，较厚的盖子设计成本更高，因此对公司产生经济影响。这些盖子到底应该有多厚？为了回答这个问题，我们需要知道北方树种（如白杨和云杉）的根系是如何受到覆盖厚度的影响的-这些种植树木的根系实际上占据了整个土壤剖面，还是由于向上迁移的盐剖面而仅限于土壤表面？北方树种的根是否表现出足够的可塑性，在这些盐度条件下发展，以支持一个健康的森林，以及如何在这些填海复盖模仿自然盐碱或非盐碱地上发现的根分布？最近的研究表明，从这些开垦景观中收集的根系样本在高盐超载中被发现。然而，我们不知道这些根是否属于所需的北方树种种植在那里，或从林下植被或杂草，因为形态根识别技术的不足。因此，本建议的目标是：1）按物种确定生根分布（白杨、云杉、选择的林下植物）在天然林分、天然盐碱地和不同厚度的开垦盐碱地景观中使用DNA测序技术及其形态特征; 2）使用微型电子管量化复垦景观与自然林分相比的根系动态和活性（地面中的透明管，其使用相机来捕获根图像）和示踪剂技术与DNA测序相结合;以及3）使用3D根结构模型来确定白杨和云杉根对盐碱条件的可塑性。对于目标1，将从不同厚度的天然林分、天然盐碱地和开垦的盐碱地景观中收集根系，并利用DNA测序技术进行鉴定，以最终了解根系在土壤剖面中的分布位置。还将测量根系特征，以确定与天然和天然含盐场地相比，覆盖层和覆盖层之间根系的可塑性。目标2中的根系动态将在复垦和自然场地中使用微型电子显微镜进行测量，其中将透明塑料管插入地面，并使用微型摄像机每月收集根系图像。将使用放置在不同深度并在植被地上部分测量的稳定示踪剂来测量根系的活性。为了研究目标3中这些根系的根可塑性，将使用三维根构型模型，输入参数从挖掘的根系中获得，以模拟不同覆盖厚度和迁移盐剖面对根可塑性和根发育的影响。该项目的新颖之处在于，它使用DNA测序技术来实际识别单个根，以了解覆盖厚度如何影响根的发育，从而影响树木的生长，并为预测盐和覆盖厚度对根发育的影响提供工具。该计划将提供对油砂公司和监管机构认证回收景观具有重要意义的结果，并通过确保根系与天然林相比正常发育，最大限度地降低覆盖失败的风险。

There are about 6500 ha of reclaimed landscapes in the oil sands region, the majority of which consists of materials with high levels of salts in the overburden that is capped on top with a peat/mineral soil cover up to 1.5 m thick. The thickness of these covers has ecological implications in that thicker covers will minimize negative effects of salt migration from the overburden into the cover on root systems but also reduce water yield for downstream wetlands. In addition, thicker covers are more expensive to design and thus have economic ramifications for companies. How thick should these covers actually be? To answer that we need to know how root systems for boreal species such as aspen and spruce are impacted by cover thickness - do roots of these planted trees actually occupy the entire soil profile, or are they restricted to just the soil surface due to the upward migrating salt profiles? Do roots of boreal species demonstrate enough plasticity to develop under these salinity conditions in order to support a healthy forest and how do root distributions on these reclaimed covers mimic root distributions found on naturally saline or non-saline sites? Recent research has shown that root samples collected from these reclaimed landscapes are found in the high salt overburdens. However, we do not know if these roots belong to the desired boreal tree species planted there or from understory vegetation or weeds because of inadequacies of morphological root identification techniques. Therefore the objectives of this proposal are to 1) determine the rooting distribution by species (aspen, spruce, selected understory) using DNA sequencing techniques and their morphological traits in natural stands, naturally saline sites, and reclaimed saline-sodic landscapes of varying thickness; 2) quantify root dynamics and activity in reclaimed landscapes compared to natural stands using minirhizotron (clear tubes in the ground that use cameras to capture root images) and tracer techniques coupled with DNA sequencing; and 3) determine the plasticity of aspen and spruce roots to saline-sodic conditions using 3D root architecture models. For Obj. 1 roots will be collected from natural stands, naturally saline sites, and reclaimed saline-sodic landscapes of varying thickness and identified with DNA sequencing techniques to conclusively know where in the soil profiles the root systems are distributed. Root characteristics will also be measured to determine the plasticity of the roots between the overburden and cover layers compared with natural and naturally saline sites. Root dynamics in Obj. 2 will be measured in reclaimed and natural sites using minirhizotrons where clear plastic tubes are inserted into the ground and root images collected on a monthly basis with a miniature video camera. The activity of the roots will be measured using stable tracers placed at various depths and measured in the aboveground portion of the vegetation. To investigate root plasticity of these root systems in Obj. 3 a 3D root architecture model will be used with input parameters obtained from excavated root systems to model the effect of varying cover thicknesses and migrating salt profiles on root plasticity and root development. This project is novel in that it uses DNA sequencing techniques to actually identify individual roots to understand how cover thickness is affecting root development and thus tree growth as well as providing a tool for predicting the effects of salts and cover thickness on root development. This program will provide results that are significant to oil sand companies and regulators in certifying reclaimed landscapes and minimize risks of cover failure by ensuring that root systems are developing properly compared to natural forests.