INVESTIGATION OF THE HYDRAULIC CHARACTERISTICS OF COASTAL REDWOODS THROUGH ANALYSIS OF WATER DYNAMICS

89 pagesIn recent years, the increased variability in weather during the climate change disturbs the global water cycle and harms the earth ecosystem. Because trees provide critical ecosystem services, it is important to understand how they respond to the changing environment to gauge the negative impact of the climate change on the ecosystem. Water is crucial for tree survival. The sessile nature of the trees requires them to be robust to the microclimate changes in water availability around them. Plants constantly face the compromise between being able to take in carbon dioxide to conduct photosynthesis and having to lose water. Water evaporative demand induces tension on water in a tree that can be harmful if it rises beyond a certain level. Thus, a tree needs to maintain a proper level of internal water status under sub-diurnally, diurnally, and seasonally changing water evaporative demand. The problem of maintaining water status is even more prominent when the tree is challenged by the hydraulic limitations of being tall. In this case, the tree’s hydraulic design can provide basic and energy efficient mechanisms for the tree to manage water well. The hydraulic design is based on the physiological and architectural properties of the tree. In this thesis, I aim to answer the question of how the redwood is designed to transport and store water. I will investigate the hydraulic characteristics of the coastal redwood through analysis of water dynamics as captured by a collaborator’s measurement of stem water potential, sapflow, and microclimate variables. Based on my analysis, I draw preliminary conclusions about variations of properties as a function of axial position along the three’s height. The importance of stored water in meeting diurnal water evaporative demand is recognized. I also propose a possible mechanism to suppress high frequency excursions of stress based on variable constitutive properties.2023-06-0