- Author: Kat Kerlin
Reposted from the UC Davis College of Agricultural and Environmental Sciences news
Redwood Trees Have 2 Types of Leaves, and They Do Totally Different Things
- Redwoods have two types of leaves, one to make food and the other to absorb water
- Study is first to estimate whole-crown water absorption in a large, mature tree
- Leaf types shift places on the tree depending on if environment is wet or dry
- Findings can help scientists monitor trees' adaptability amid a changing climate
Redwoods are among the most well-studied trees on the planet, and yet their mysteries continue to surprise and delight scientists and nature lovers.
Scientists from the University of California, Davis, discovered that redwood trees have two types of leaves, and those leaves have completely different jobs, according to a study in the American Journal of Botany. Together, these functionally distinct leaves allow the world's tallest trees to thrive in both wet and dry parts of their range in California, without sacrificing water or food.
Division of labor
The peripheral leaf spends its working hours making the tree's food — converting sunlight into sugar through photosynthesis. Its colleague, the axial leaf, does almost nothing to help with photosynthesis. Instead its specialty is to absorb water. In fact, the study found that a large redwood can absorb up to 14 gallons of water in just the first hour its leaves are wet.
How does that compare to other trees? Scientists don't know. This is the first study estimating whole-crown water absorption in a large, mature tree. Because large redwoods have over 100 million leaves, this absorption record may prove hard to beat.
In wet forests, photosynthesis can be inhibited by films of water covering leaf stomata when they get wet. For redwoods, the different leaf types allow the trees to get wet and still be able to photosynthesize. The peripheral leaves have a waxy coating that slows water absorption but may help them continue photosynthesis throughout the wet season.
“I'd be surprised if there weren't a lot of conifers doing this,” said lead author Alana Chin, a Ph.D. student in ecology with the UC Davis Department of Plant Sciences at the time of the study. “Having leaves that aren't for photosynthesis is in itself surprising. If you're a tree, you don't want to have a leaf that's not photosynthesizing unless there's a very good reason for it.”
The study also found that leaves can shift their “office space” along the tree depending on whether the environment is wet or dry.
In the wet, rainy north coast, the water-absorbing leaf type is found on the tree's lower branches, leaving the upper, sunnier levels to the photosynthesizing leaf type. That dynamic flips for redwoods in their southern range: The water-collectors live among the tree's higher levels to take more advantage of fog and rain, which occur less often in the drier environment.
To arrive at their findings, the authors collected shoot clusters from six redwood trees at five forest locations stretching from wet Del Norte County to the dry Santa Cruz Mountains and exposed them to experimental fog. They estimated the water absorption potential for seven additional trees — including the tallest living tree — and took samples at varying heights.
They then compared the anatomy and measured photosynthesis of the peripheral and axial leaves to understand their function. They also developed a physics-based causal model that allowed them to determine the leaf traits that regulate absorption rates.
Amid all the findings, Chin is most excited to have found an easy and effective way to indicate redwood trees' ability to access fog. Researchers can monitor how and if redwoods are adapting to climate conditions and a future, drier world by simply looking at the visible waxes covering the two types of leaves — something that could be captured on a cell phone camera and shared by other scientists or even members of the public.
Redwoods are renowned for their resilience in the face of many natural threats and inspire numerous superlatives: They are among the planet's biggest, tallest, oldest trees. They have tannin-rich heartwood, fire-resistant bark and pest-resistant leaves. This new finding is another example of their ability to respond to environmental conditions, like drought and water stress.
“The cool thing here is their ability to thrive under all these circumstances and adjust themselves to these different environments,” said Chin, who grew up near the redwoods in Mendocino County. “That things like this can be happening right under our nose in one of the best-studied species out there — none of us assumed this would be the story.”
Study co-authors include Paula Guzman-Delgado, Jessica Orozco, Zane Moore and senior author Maciej Zwieniecki of the UC Davis Department of Plant Sciences, as well as Stephen Sillett, Lucy Kerhoulas and Marty Reed of Cal Poly Humboldt, and Russell Kramer of Dipper and Spruce LLC in Washington.
The study was funded by the National Science Foundation and a Katherine Esau Fellowship from UC Davis.
- Author: Richard B. Standiford
- Author: Jaime Adler
The Coast Redwood Forests in a Changing California Science Symposium was held June 21-23, 2011 at UC Santa Cruz with just under 300 registrants in attendance. Participants ranged in background from graduate level students to university forestry faculty, land managers, and conservation groups, public agencies, and land trust members. The symposium was strategically held in Santa Cruz, near the Southern end of the redwood region. Designed to present the state of our knowledge about California’s coast redwood forest ecosystems and sustainable management practices, this symposium was built on earlier redwood science symposia held in Arcata, CA in June, 1996 and in Santa Rosa, CA in March, 2004.
Seed funding for the Symposium was from the University of California/California State University competitive grant program. Rick Standiford of UC Berkeley, Doug Piirto of Cal Poly San Luis Obispo, and John Stuart of Humboldt State Univeristy served as the three co-chairs of the symposium.
Link to Proceedings
The Proceedings were produced as a General Technical Report of the USDA Forest Service It is available on-line as well as a limited number of printed copies from the USDA Forest Service Pacific Southwest Research Station. The entire Proceedings or individual papers can be downloaded by clicking HERE. The full citation for the Proceedings is:
Standiford, Richard B.; Weller, Theodore J.; Piirto, Douglas D.; Stuart, John D, technical coordinators. 2012. Proceedings of coast redwood forests in a changing California: A symposium for scientists and managers. Gen. Tech. Rep. PSW-GTR-238. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 626 p.
Field Tour Information
The first day of the symposium consisted of two simultaneous field tours, one to the North County and one to the South County. The North County tour focused on active redwood timber management on corporate ownerships operating under the unique policies that dictate decision making on the central coast, and Cal-Poly’s forest management and research at its Swanton Pacific Ranch. It also included, a brief tour of the Big Creek Lumber Company sawmill and a visit to areas burned in the more than 7,000 acre Lockheed Fire of 2009. The South County tour traversed the range of redwood forest conditions from the old growth of Henry Cowell State Park and the uncut 120 year old young growth of Nisene Marks State Park to uneven-aged young growth stands established by individual tree selection harvesting on non-industrial forestlands.
Opening remarks started the second day of the symposium and began the academic concurrent sessions. Local historian Sandy Lydon spoke about the special history of the redwoods in the region, recounting stories from his boyhood about roaming through the forests and giving a brief synopsis of the settlement of the area. Steve Sillett, Humboldt State University forestry professor, described his experiences climbing the redwoods and his discoveries in the redwood forest canopy ecosystems, as well as his findings on tree growth from dendrochronology measurements. Ruskin Hartley, Executive Director and Secretary of Save the Redwoods League, called on the audience to set “audacious goals and collaborative actions.” He maintained that nature does not develop boundaries and that in moving forward, we should focus on a shared set of goals and that public and private land should progress simultaneously. Concluding the session, Ron Jarvis, Home Depot’s VP of sustainability talked candidly about the role of environmental sustainability practices and policies as part of the home improvement retailer’s business model. He noted that when he began in the sustainability department he undertook a two year long project to understand where every sliver of wood from over 9,000 products originated to ensure sustainable wood practices.
Over 75 concurrent oral presentations were showcased over two days, pertaining to the topics of: Ecology (15 presentations); Silviculture and Restoration (11 presentations); Watershed and Physical Processes (22 presentations); Wildlife, Fisheries, Aquatic Ecology (10 presentations); Forest Health (10 presentations); Economics and Policy (6 presentations); Monitoring (7 presentations). In addition, almost 40 posters were displayed during the evening reception, ranging in topic from post-fire response, to long-term watershed research, and community forestry models. Held outside on the warm Santa Cruz evening, participants enjoyed a strolling dinner and networking with colleagues, making the reception a highlight of the symposium.
Conclusions and Summary
The symposium concluded with closing remarks about the future of research in the redwood region from John Helms, UC Berkeley and Mike Liquori, Sound Watershed. In addition, a panel including Dan Porter, the Nature Conservancy, Lowell Diller, Green Diamond, and Kevin O’Hara, UC Berkeley discussed the interface of research, management, and conservation. The overall discussion led to the conclusion that academic research and applied research should be made available to the field as a whole as findings progress and that more opportunities for networking and interactions should be made available to the forestry community.
Overall, the symposium fulfilled its purpose to identify key knowledge gaps, bring together multi-disciplinary teams, and help identify future opportunities for collaboration. Participants were pleased with the presenters and research shown. Many noted that a highlight of the symposium was being able to meet and interact with others whose works they had previously cited in their own research. Of the approximately one half of participants who completed the follow-up survey, 100% hoped to see more events like the 2011 Redwood Symposium.
- Author: Jaime Adler
June 21-23, 2011
University of California, Santa Cruz
Policies and strategies guiding the use and management of California’s coastal ecoregion are dependent on objective scientific information. Attention to this region has increased in recent years. At the same time, much new information has been collected. Each year the array of decisions affecting lands and natural resources in the redwood region carry more weight; evidence the recent interest in watershed assessment, fish and wildlife recovery efforts and silvicultural changes. This symposium is part of a continuing effort to promote the development and communication of scientific findings to inform management and policy decisions.
The symposium is intended for anyone involved in the research, education, management, and conservation of coast redwood systems. This includes RPFs, landowners and managers, community and conservation groups, land trusts, and policy makers.
Poster abstracts are still being accepted!
Register before fees increase! (On May 21st fees increase $50. On June 21st fees increase an additional $50.)
For more information or to register, please visit http://ucanr.org/sites/Redwood/