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发芽，形成树冠上的附生植物垫。这些草席通过树冠中活的和死的植物的积累形成了类似土壤的结构。然而，这些根是否吸收了大量的水分和营养，还没有被测量，甚至没有得到证实。根部可能转移的养分和水资源可能对树木的健康和生长有相当大的好处。这项博士论文改进基金将提供资金来研究附生垫和在冠层土壤下扎根的寄主树木之间的水和养分交换。太平洋西北地区的气温可能会继续上升，干旱会变得更加严重。冠层根和附生植物可能对维持关键栖息地的植物生物多样性至关重要，并且具有优势，特别是在树木受到热胁迫的条件下。该项目的成果将显著提高生态修复计划的有效性。此外，学生，包括那些来自弱势群体的学生将参与这个项目，获得宝贵的科学研究经验。本项目将评估冠层根系活动、冠层水分再分配和不定根的生理生态作用。将采用三种方法来实现这些目标：实验室、温室和田间试验。（需要提到的实验室实验）温室试验的目的是模拟植物之间的水分关系（在一个简化的系统中）通过树冠根的附生植物和寄主树使用杨树（Populus trichocarpa）。初步数据表明，该杨树系统的冠层根系具有吸水性，并提示树内潜在的双向水流（即向上和向下的液流）。数据还表明，有树冠根的树木可以通过从附生植物席中吸收水分来缓解干旱状况。将采用类似的程序来确认这些活动也在西澳奥林匹克国家公园的野外条件下发生。在那里，重点将放在大叶枫树（Acer macrophyllum）上，它们会自然地形成树冠根。稳定同位素将用于跟踪不同季节从树冠根部到树木其他部位的水分输送，并了解不定根在不利水分条件下的生理和生态作用。

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.