Sequoia sempervirens (California's coastal redwood) is well known as the tallest tree in the world, with some individuals reaching 115 meters tall. Recent research has uncovered a unique physiological adaptation that allows these trees to deal with the stress of transporting water from the root system to upper branches of the canopy. When ground water stores are depleted during the long, dry summers, S. sempervirens is able to absorb water that condenses on its leaf surfaces during seasonal fog events. It is hypothesized that a community of fungi living on and within the leaves of S. sempervirens aid in the foliar absorption of water. The proposed research will first sample and characterize the foliar fungal community present in different parts of the redwood trees and from different areas of the coastal forests using molecular 'barcoding'. Stable isotope-labeled fog in glasshouse experiments will be used to determine if the presence of foliar fungi increases the tree?s ability to absorb water through its foliage, and if so which fungal communities found in association with S. sempervirens are the most effective at aiding water absorption. Finally, C13-labeled carbon dioxide will be used to track the possible transfer of carbon (in the form of sugars) from the host to the fungi, suggesting a symbiotic relationship between the tree and the fungal community it harbors.
This research will help to characterize the microbiome of the california coastal redwood, an economically and ecologically important keystone species. Understanding the role of the fungal community in sustaining redwood trees will have important consequences for sustainable forestry practices, especially as drier summers become more common and foliar uptake via fog may play an increasingly important role in forest health. This research additionally demonstrates the important positive role that fungi can play in ecosystem dynamics. This research will be incorporated into three hands-on lesson plans for K-12 students that illustrate the hidden, microscopic diversity and complex species interactions in the natural environment around them. These lesson plans will be incorporated into the NSF funded GK-12 program "Exploring California Biodiversity" and utilized in the "Teaching MadScience" after school program held at two Middle Schools in the Berkeley, CA Public School District. The support will also result in the completion of a doctoral dissertation by a female scientist and the training of two undergraduate research apprentices in laboratory and computational techniques for studying fungal diversity and community ecology.
Project Outcomes: Sequoia sempervirens is well known as the tallest growing tree in the world with the tallest towering at 115meters tall. Recent research has uncovered a unique physiological adaptation of S. sempervirens that allows these trees to deal with the stress of transporting water from the root system to upper branches of the canopy. When ground water stores are depleted, S.sempervirens is able to absorb water that condenses on its leaf surfaces during fog events. While it is known that this does occur is not known how. The dissertation of co-PI Kali Lader directly tested the hypothesis that the many foliar endophytic and epiphytic fungi that S. sempervirens is host to are aiding in the foliar absorption of water. The funded research followed two main aims; first to sample and characterize the foliar fungal endo/epiphyte community using molecular techniques including next-generation sequencing advances. Second, to use stable isotope labeled fog in glasshouse experiments to demonstrate that the presence of foliar fungal endo and epiphytes increased the redwood tree’s ability to absorb water through its foliage. These glasshouse experiments also demosntrated a clear difference in water absorption ability between the different fungal communities that are found in association with S. sempervirens, sugesting the importance of fungal community monitoring to ensure S. sempervirens survival. A third goal, to label the sugars of the host using 13C labeled carbon dioxide and track the possible transfer of carbon from the host to the chitin of its fungal symbionts, is being continued as a postdoctoral project. Intellectual Merit This research has opened a new avenue of research in the field of endo/epiphytic fungi. A direct positive physiological role was established for epiphytic fungi for the first time, and was placed into a systematic and evolutionary context. The results demonstrated the important nature of the plant/fungal interactions for S.sempervirens physiology andecology, and demonstrated that the fungal community composition was highly structured based on age class of foliage and position of the tree within the redwood stand (Lader, Hepp, Dawson and Specht in prep). The information gained from this study is being used by current graduate students in the Dawson lab to explore specific mechanisms of foliar absorption of water in S. sempervirens. These results may have implications in other fog driven environments where similar associations could be present. The fungal community composition will be important to monitor over time, as its clear that changes in the composition with climate changes will impact the plants ability to exist in its current range (Lader, Specht and Dawson in prep). Broader Impacts Co-PI Lader trained and mentored 4 undergraduate students, one of whom presented her results as an honors thesis in the College of Natural Resources, and received a masters degree as a result of this funded research. She is currently working at the intersection of science and education, developing exploratory natural history-based curricula for middle-school science classrooms in California public schools. Data from this research was also used to develop two educational units including hands-on laboratories and lesson plans on plant / fungal interactions for the NSF GK-12 program "Exploring California Biodiversity."
