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

温带雨林和热带雨林中的树木可以从树枝上长出根，进入树冠上的附生植物垫子。这些垫子通过在树冠上积累活的和死的植物来形成类似于土壤的结构。然而，这些树根是否会吸收大量的水分和养分，还没有得到测量，甚至还没有得到证实。潜在通过根部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。这项博士论文改进补助金将提供资金，以研究附生垫子和在树冠土壤下生长的寄主树木之间的水分和养分交换。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。树冠根部和附生植物对于维持关键生境中的植物生物多样性可能是至关重要的，并传达了一种优势，特别是在树木受到高温胁迫的情况下。这项工程的成果将显著提高生态修复计划的有效性。此外，包括来自代表性不足群体的学生将参与这一项目，获得宝贵的科学研究经验。该项目将评估冠层根系活性、冠层水分再分配以及不定根的生理和生态作用。将使用三种方法来实现这些目标：实验室、温室和田间实验。(值得一提的是实验室实验)温室实验旨在通过杨树(毛果杨)的树冠根部模拟附生植物和寄主树木之间的植物水分关系(在一个简化的系统中)。初步数据表明，在这个杨树系统中，树冠根部有水分吸收，这表明树内存在潜在的双向水流(即向上和向下的液流)。数据还表明，有树冠根部的树木可以通过从附生植物垫子中吸收水分来缓解干旱条件。类似的程序将被用于确认这些活动也发生在田野条件下的奥林匹克国家公园，华盛顿州。在那里，重点将放在大叶枫树上，这种枫树可以自然地形成树冠的根。稳定同位素将被用来跟踪水分在不同季节从树冠根到树的其他部分的运输，并了解不定根在不利的水分供应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.