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Research suggests some trees have potential for immortality
UNR researcher teams with Italian collaborator in new paper
Large, majestic trees are iconic symbols of great age among living organisms, yet published evidence suggests that trees do not die because of genetically programmed age deterioration, but rather are killed by an external agent or a disturbance event. And, they can be a record of thousands of years of environmental change, especially in Nevada.
“These ancient trees are indicative of the enduring landscapes that surround us,” Franco Biondi, a professor at the University of Nevada, Reno and co-author of the paper said, “and a reminder of the value of having such long-lived organisms within them.”
Biondi and co-author Gianluca Piovesan, a professor at the University of Tuscia, Italy, are both dendrochronologists, researchers who date events, environmental change and archaeological artifacts by using the characteristic patterns of annual growth rings in timber and tree trunks. Biondi directs the DendroLab at Nevada, and is part of the University’s College of Agriculture, Biotechnology & Natural Resources. Piovesan directs the Dendrology Lab at Tuscia, and is in the Department of Agriculture and Forest Services.
In their paper about tree longevity published in the August edition of New Phytologist, as a Tansley Review, they find that the “cambium,” which is the growth tissue area between the bark and the wood, appears immune to senescence, which is defined as the intrinsic age-dependent increase in mortality or deterioration in performance under the control of an internal biological clock. Theoretically then, trees could be immortal organisms, and gene expression analyses are starting to uncover the processes that maintain a balance between growth and aging processes in old trees.
The paper also cites wildfires, droughts, insect outbreaks, bacteria, viruses and fungi, as well as human impacts, as the external forces causing tree mortality. The authors suggest that because large old trees may be affected by ongoing and future global changes in climate, land use and disturbance regimes, a solid scientific understanding of maximal tree lifespans is needed to design optimal conservation policies and management strategies.
“Trees are natural archives of environmental change, and tree longevity gives us that long-term look at the history of natural and human impacts on our world,” Biondi said. “The value of old trees as archives of environmental variability and abrupt events, which has long been recognized for temperate and high-latitude areas, has recently been extended to tropical forests. At the same time, the distribution of old-growth forests has been reduced greatly by human impacts.”
In their paper, Biondi and Piovesan argue that tree longevity is a key trait for global syntheses of life history strategies, especially in connection with disturbance regimes and their possible future modifications.
“It’s becoming possible to evaluate how long the trees have withstood natural disturbances,” Biondi said.
Biondi says capacity to exceed 2,000 years of age has been demonstrated for six types of conifer trees, including types of juniper, sequoia, cypress and pine. Other conifers include dendrochronologically tested trees with ages in excess of 1,000 years, such as Agathis, Australian pine and Douglas-fir, to name just a few.
Tree size, both girth and height, varies greatly for trees of the same age, and is therefore not a reliable indicator of maximum lifespan. As a general, practical rule, which is explained and supported by research presented in their review, “the largest trees are not the oldest ones,” especially within a species. More reliable indicators of old age can be found in crown and bark characteristics, as well as partially exposed root systems.
Long tree lifespans are allowed within areas that support resistance to, or avoidance of, mortality from outside forces. Another requirement for trees to achieve their maximum longevity is either sustained growth over extended periods of time or at least the capacity to increase their growth rates when conditions allow it.
“It’s not just human impacts, there are multiple impacts,” Biondi said. “However, one timely message is that we often do not understand how to best manage forests. Based on long historical perspectives, if we protect the forest too much (like fire suppression for the past 100 years) the forests will not be so healthy. For example, Sequoias need fire to regenerate. They can’t reproduce if the density between trees gets filled in with other species, so surface fires might give them another chance to thrive.”
Biondi, whose research is in part supported by the University’s Experiment Station, points out that while there are extremely old trees around the world, some of the best examples are right here in the Great Basin of Nevada.
“We have landscapes in our state that show extreme resilience, and these ecosystems have been there thousands of years,” he said. “It’s a reminder that ecosystems are more resilient than we think. In some areas of the Great Basin, there were many more fires before settlement, from 1500 to 1800, than in the last two centuries.”
In their paper, Piovesan and Biondi also explicitly challenge the long-held notion that shade-tolerant, late-successional species are long-lived compared to early successional species. They say to forget what you learned in any intro biology or ecology course about how trees grow within their ecosystems. The idea of succession, where fast-growing trees give way to old, slow-growing trees, just isn’t the case on most Great Basin mountains.
“The classic view of ecology is that forests go through stages – succession,” Biondi said. “Since the 1950s the idea that the ecosystems are like organisms – with climax species on a trajectory – is based on European and Eastern American views. Where we live, here in the Great Basin, there’s plenty of evidence that this doesn’t happen, and species such as bristlecone pine, which includes trees as old as five thousand years, are both pioneer and climax – or neither one. They are not replaced by any other species. It’s been staring at us in the face all these years: tree species with extreme longevity do not fit the successional paradigm.”
Identifying extremely old trees is therefore the groundwork not only for protecting and/or restoring entire landscapes, but, based on long historical perspectives, also for revisiting and updating classic ecological theories that shape our understanding of environmental change.
By Mike Wolterbeek, Communications Officer | 775-784-4547 | mwolterbeek@unr.edu
Snow cover critical for
revegetation following forest fires
Study finds climate change a factor in decrease of snowpack in the Western United States
With wildfires devastating mountain ecosystems across the western US, successful forest revegetation recovery hinges on, among other factors, an adequate lasting snowpack, according to research by the University of Nevada, Reno and Oregon State University.
“Our study illustrated that summer precipitation, snow cover and elevation were all important drivers of revegetation success,” said Anne Nolin, a hydrologist and geography professor at the UNR and formerly at OSU. “In particular, we found that snow cover was a critical explanatory variable for revegetation in the Oregon and Washington Cascades. This could help inform revegetation management practices following severe wildfires.”
Climate change has already increased the fraction of winter precipitation that falls as rain rather than snow, reduced the spring snow water equivalent – a metric for how much water snow contains – and caused snowmelt to begin earlier in the spring than it used to, Nolin explained. Pacific Northwest snowpacks have seen the greatest declines of any seasonal snow region in the West.
The research, led by Nolin, examined the 260,000-square-mile Columbia River Basin in the Pacific Northwest. She teamed with co-author Andrew Wilson, a graduate research assistant in OSU’s College of Earth, Ocean, and Atmospheric Science, and co-author Kevin Bladon of OSU’s College of Forestry for the study.
The NASA-supported study featured before-and-after vegetation analyses for two dozen high-severity wildfires. The fires occurred over a 10-year period among the four distinct subregions of the Columbia River Basin. There are many short- and long-term effects from these fires, including erosion, debris flows and water quality issues, which can affect the health of aquatic ecosystems and downstream community water supply, highlighting the importance of understanding post-fire forest rehabilitation.
In their paper… findings show that, given the trends of increasing wildfire activity, lower snowpacks, and earlier snow disappearance dates across the Pacific Northwest, forests will likely experience more frequent drought conditions, which will negatively impact the success of post wildfire vegetation recovery with a number of impacts to the ecosystem.
“This knowledge may be used to facilitate adaptive post-fire management policies and decisions to ensure long-term forest health,” Nolin, who is also director of the UNR’s Graduate Program of Hydrological Sciences, said. “For example, depending on the sub-region and species composition, reseeding efforts following low snow winters might employ more drought tolerant species or, replanting could be delayed one to two years until snowmelt and soil moisture conditions are more favorable for seedling propagation.
“However, climate change projections and shifting wildfire regimes have increased concerns about post-fire regeneration and, as such it is imperative that we broaden our understanding of the role of snowpacks in post-wildfire forest regeneration. The snowpacks’ role in aiding revegetation will become increasingly important across the West. And where snowpacks have declined, there likely will be ecosystem transitions that look like a shift from forest to non-forest and from evergreen to deciduous vegetation.”
Wildfires continue to burn more area each year across many regions of the planet, including the Pacific Northwest. The Pacific Northwest’s largest watershed, the Columbia River Basin contains a variety of fire-prone landscapes that have seen almost 900 fires since 2010, serves as critical habitat for more than 700 species and is a water source for seven states.
“As wildfire activity continues to increase and intensify in the Northwest, understanding what shapes revegetation on severely burned forested landscapes is vital for guiding management decisions,” co-author Bladon said.
After the occurrence of a wildfire, revegetation over the burned area is critical to maintain or re-establish ecosystem functions from forests such as biodiversity, erosion control, water purification and habitat provision.
“Snow matters to regrowing vegetation following fire, and with double impacts of declining snowpacks and increasing wildfires it is critical that we understand how these changes are affecting Pacific Northwest forests,” Nolin said. “Positive relationships between snow cover and summer precipitation with post-fire greening suggest that active post-fire revegetation efforts will help facilitate recovery, especially during years when severe wildfires are followed by early snowmelt years or below average summer precipitation.”
In the study, summer precipitation consistently appeared as the most important variable driving post-fire revegetation across all four subregions. Snow cover frequency, along with elevation, were shown to be secondary but significantly influential explanatory variables for revegetation in the Oregon and Washington Cascades. More than 80% of wildfires in the western United States from 2000 to 2012 burned within a seasonal snow zone, a time period that overlaps with the years studied by the scientists.
“As wildfire activity continues to increase and intensify in the Northwest, understanding what shapes revegetation on severely burned forested landscapes is vital for guiding management decisions,” Bladon said. “But variables such as snow cover frequency, pre-fire forest composition, and elevation, were also shown to be significantly influential for revegetation in the Oregon and Washington Cascades.”
Wildfire season length in the western U.S. overall has increased by roughly 25 days in recent decades, including a massive increase in the Northwest from the mid-1970s, when it was 23 days, to 116 days in the early 2000s. That’s attributable mainly to warmer temperatures and drier conditions in the spring and summer.
“Snow cover has a strong influence on postfire vegetation greening, but the influence varied depending on subregion and dominant prefire conifer species, with the biggest impacts at low to moderate elevations in the Washington Cascades, the Oregon Cascades and western Montana Rockies,” Nolin said. “And with current climate change projections, snowpacks’ role in aiding revegetation will become increasingly important across the West.”
Bladon suggests fire can be looked at as an opportunity for forests to reassemble into ecosystems better suited to survive warmer winters, longer fire seasons and drought stress.
“That’s at the heart of the challenge of reconciling a changing climate’s ecological forces with postfire forest management goals – the goals are often oriented toward re-establishing forests as they existed before the fire,” Bladon said. “But with shifting climate trends in the region, that might not be the most adaptive path forward for forested landscapes.”
Researcher returns to Nevada to make genetic improvements in animal herds
Andrew Hess joins the College of Agriculture, Biotechnology & Natural Resources
UNR recently welcomed Assistant Professor Andrew Hess to the Department of Agriculture, Veterinary & Rangeland Sciences. Hess will be focusing his research on innovation in breeding and genetics using University herds and flocks.
As part of the University’s Experiment Station, Hess will be working with cattle and the 1,800 head of Rafter 7 sheep at the Great Basin Research & Extension Center located in Eureka. The Rafter 7 sheep, initially developed about 30 years ago at the University’s Experiment Station under the direction of Professor Emeritus Hudson Glimp, are famous for their fine wool and heartiness on marginal grazing lands. The Center, which opened last summer, addresses the related issues of sustainable grazing management of dryland rangelands; livestock and crop production under water-limited environments; and alternative water and irrigation strategies for crop production.
Hess will be conducting genetic research to breed animals that are more resilient and adaptable to climate change and disease. He is also collaborating with the United States Department of Agriculture on multiple projects, including studying the litter sizes of lambs born into highly prolific sheep breeds and researching internal parasites of sheep. His research will benefit herds across northern Nevada by increasing their resilience while requiring less intervention to maintain high levels of performance.
Hess will also be continuing work that he started during his post-doctoral position at AgResearch, one of New Zealand’s Crown Research Institutes. There, he worked with a variety of animals, such as goats, deer, sheep and mussels, to identify genetic markers that can be used to more accurately select animals for production traits.
He graduated from the University with his B.S./M.S. degree in biotechnology and is excited to return after having earned his doctoral degree at Iowa State University.
“I grew up in Nevada and attended UNR, so this was a great opportunity to work close to home,” Hess said. “I’m excited to serve the community that helped me get where I am today.”
Cattlemen’s Update returns to provide market, production & research updates
In-person and virtual educational programs to be held at seven locations across Nevada
The University of Nevada, Reno will host the annual Cattlemen’s Update in person and virtually in 2022, Jan. 10 – 14. For more than 40 years, the University has held several sessions across Nevada in January to provide ranchers with current research-based information about issues that may affect the efficiency, productivity, profitability and sustainability of their businesses and Nevada’s cattle industry.
The five-day event, offered virtually once and then at six locations across the state, is a partnership led by the University’s College of Agriculture, Biotechnology & Natural Resources, and its Extension and Experiment Station units. Other program partners include local sponsors and U.S. Department of Agriculture. Speakers for this year include State Veterinarian Amy Mitchell, Extension Educator for Churchill County Carson Anderson Oney, Professor and Extension Educator for Humboldt County Brad Schultz, and Associate Professor of Rangeland Sciences and Extension Specialist Paul Meiman.
At the three- to four-hour sessions, experts will discuss pertinent topics with participants, including topics on animal health and cattle markets and production. The cost is $20 per ranch per location attended, which includes lunch or dinner, event proceedings and the “Red Book” recordkeeping guide for cattle producers.
This year’s schedule includes:
Jan. 10, 10 a.m., Virtual session
This session will be offered via Zoom only. Register at https://unrextension.zoom.us/webinar/register/WN_a4ec6moBTfi6oFCdIqtRIA.
Jan. 10, 5:30 p.m., Sierra Valley, California, dinner provided
Sierra Valley Grange #466, 92203 Highway 70
Jan. 11, 10 a.m., Gardnerville, lunch provided
Carson Valley United Methodist Church, 1375 Centerville Lane
Jan. 11, 5:30 p.m., Fallon, dinner provided
Fallon Convention Center, 100 Campus Way
Jan. 12, 5:30 p.m., Ely, dinner provided
Ely Convention Center, 150 W. Sixth St.
Jan. 13, 12:30 p.m., Elko, dinner provided
Dalling Hall, 600 Commercial St.
Jan. 14, 10 a.m., Winnemucca, lunch provided
Extension Office, 1085 Fairgrounds Road
Times given for the in-person sessions are registration times, with the program beginning 30 minutes later. For more information, contact Staci Emm, Extension educator for Mineral County, at emms@unr.edu or 775-475-4227. Persons in need of special accommodations or assistance should call or notify Paul Lessick, civil rights and compliance coordinator, at plessick@unr.edu or call 702-257-5577 at least three days prior to the scheduled event.
Article Provided By:
Claudene Wharton, Senior Marketing & Communications Specialist
College of Agriculture, Biotechnology & Natural Resources
University of Nevada, Reno / MS 0405 | Reno, Nevada 89557-0404
775-784-7072 | whartonc@unr.edu