DISSERTATION RESEARCH: Canopy hydraulic redistribution: Tree water uptake via canopy roots in epiphytic bryophyte mats

温带和热带雨林中的树木可以从树枝上长出根，进入树冠中的真菌垫。这些垫子通过在树冠中积累活的和死的植物形成类似于土壤的结构。 然而，这些根是否吸收了大量的水和养分，还没有被测量甚至证实。通过根系转移的养分和水资源可能对树木的健康和生长产生相当大的好处。这个博士论文改进补助金将提供资金，以检查附生垫和宿主树木之间的水和营养物质的交换，这些树木在树冠土壤下生根。太平洋西北部的气温可能会继续上升，干旱将变得更加严重。冠层的根和附生植物可能是至关重要的，以维持植物的生物多样性在关键的栖息地，并传达一个优势，特别是在树木成为热应力的条件下。 该项目的成果将大大提高生态恢复计划的有效性。 此外，包括来自代表性不足群体的学生在内的学生将参与该项目，获得宝贵的科学研究经验。本计画将评估冠层根系活性、冠层水分再分配及不定根的生理生态作用。三种方法将用于实现这些目标：实验室，温室和田间试验。(Need温室试验被设计为使用白杨（Populus ducarpa）通过冠层根来模拟附生植物和宿主树木之间的植物水分关系（在简化的系统中）。初步数据表明，在这个白杨系统冠层根系吸水，并建议潜在的双向水流（即向上和向下的液流）的树。数据还表明，树冠根系的树木可以通过从附生植物垫中吸收水分来缓解干旱状况。 将采用类似的程序，以确认这些活动也发生在华盛顿州奥林匹克国家公园的野外条件下。 在那里，重点将放在大叶枫树（宏基macrophyllum），自然发展树冠根。稳定同位素将被用来跟踪水运输从冠层根到树的其他部分在不同的季节，并了解在不利的水供应条件下的不定根的生理和生态作用。

Trees in temperate and tropical rainforests can sprout roots from branches into epiphyte mats that occur in the tree canopy. These mats develop a structure similar to soil through the accumulation of living and dead plants in the canopy. Whether these roots take up significant water and nutrients, however, has not been measured or even confirmed. The nutrient and water resources that are potentially transferred by the roots may offer a considerable benefit to the health and growth of trees. This Doctoral Dissertation Improvement Grant will provide funds to examine the exchange of water and nutrients between epiphytic mats and host trees that grow roots underneath the canopy soil. Temperatures in the Pacific Northwest are likely to continue to rise, and drought to become more severe. Canopy roots and epiphytes may be crucial to maintaining plant biodiversity in critical habitats, and convey an advantage, especially under conditions where trees become heat-stressed. Results from this project will significantly improve the effectiveness of ecological restoration plans. In addition, students including those from underrepresented groups will be involved in this project, gaining valuable experience in scientific research. This project will assess canopy root activity, canopy water redistribution and physiological and ecological roles of adventitious roots. Three approaches will be used to accomplish these objectives: lab, greenhouse and field experiments. (Need to mention the lab experiments) Greenhouse trials are designed to simulate plant water relations (in a simplified system) between epiphytes and host trees via canopy roots using poplar trees (Populus trichocarpa). Preliminary data show that there is water uptake by canopy roots in this poplar system, and suggest potential bi-directional water flow (i.e. up- and downwards sap flow) within the tree. Data also suggest that trees with canopy roots can mitigate drought conditions by taking up water from epiphyte mats. Similar procedures will be applied to confirm that these activities also occur under field conditions in Olympic National Park, WA. There the focus will be on bigleaf maple trees (Acer macrophyllum), which develop canopy roots naturally. Stable isotopes will be used to track water transport from canopy roots to other parts of the tree during different seasons, and to understand the physiological and ecological role of adventitious roots under adverse conditions of water availability.