RAPID: Resprouting and resilience: The role of nonstructural carbon reserves in fostering the longevity of coast redwood

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Coast redwood trees are among the largest living organisms on Earth. For generations, this iconic species has been treasured by the public and served as a flagship for conservation. Intriguingly, redwoods can live for thousands of years in ecosystems that are prone to fire. The redwood’s ability to resprout, or activate dormant buds beneath the bark and grow new stems, branches, and leaves, is an adaptation that enhances survival following fire. Just as humans store fat as an energy reserve, trees store sugars and starch as reserves that provide the carbon and energy needed for resprouting. This project will use carbon dating methods to estimate how long these carbohydrates have been held in reserve. In other species, decade-old reserves have been identified in 100-year-old trees, but in ancient redwoods the reserves could be much older. Research will be conducted at Big Basin Redwoods State Park, near Santa Cruz, CA, where trees are up to 2500 years old and 100 meters (330 ft) tall. On August 19, 2020, the CZU Lightning Complex Fire burned through the Park, presenting a unique opportunity to look at resprouting in very large, old trees. The project will communicate the fascinating science of redwood trees to the public, to whom these trees have universal appeal. Specific activities will include radio and video stories developed in collaboration with Northern Arizona University media specialists and an in-person outreach event.Wildfire is a common occurrence in California, and fire chronologies indicate that many coast redwood (Sequoia sempervirens) groves experience fire every 10-25 years. However, fires of the size and severity that occurred during 2020 are unprecedented. The principal question this project addresses is, “How old are the nonstructural carbon [NSC] reserves used to support resprouting in fire-damaged redwood?” A previously-developed conceptual model hypothesizes links between tree vigor and the size and turnover time of stored NSC reserves. This model predicts that the tallest, dominant, and most vigorous trees will have large reserves of young NSC (recent photosynthate, removed from the atmosphere within the last year), whereas less vigorous trees will have smaller and older NSC reserves. How old NSC reserves are in long-lived trees is unknown. This project will collect epicormic sprouts and stem wood cores from fire-damaged trees in Big Basin Redwoods State Park, and determine the age of NSC in those samples (time since removal from the atmosphere) by measuring its 14C signature on the new MICADAS (Mini Carbon Dating System) AMS (Accelerator Mass Spectrometer) at Northern Arizona University. This project will be the first to investigate NSC in redwood and the first to use 14C methods to estimate the age of NSC reserves that are being drawn on to support redwood resprouting. This work has the potential to transform understanding of the biology of this unique and long-lived species.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.