Reading The Redwood Rings – August 18, 2010

Friday, August 20, 2010

Humboldt Redwoods State Park contains many of the world’s tallest trees. Photos by Kym Kemp

Kym Kemp

Eye Correspondent

HUMBOLDT – For centuries, the coastal redwoods and giant sequoias have stood as tightly furled scrolls holding ancient writings inscribed by rain and fog and drought.

Today, a group of scientists, with the help of technology, has crafted a way to read those scrolls without destroying them. With the information gathered, the Save the Redwoods League (which is funding the team) hopes to create strategies to protect these living towers from the impact of climate change.

Like the dinosaurs (and at roughly the same time), the redwood forests once ranged across the earth. Recently in historical terms, they dwindled to the western edge of the North American continent. When the ’49ers came to California to mine for gold and stayed to harvest the natural resources, the redwoods around San Francisco fell before the invading armies, leaving barren hills stretching into the distance.

The first conservationists who came north were awestruck by the untouched miles of huge redwoods, and responded by creating what has become Humboldt Redwoods State Park. The trees in this forest, long known as some of the tallest in the world, have waited, holding their secrets tightly, until this group of scientists arrived to read the redwoods.

According to Ruskin Hartley, executive director of Save the Redwoods League, “Locked within the very rings… there’s a record of everything these trees have experienced in their life span. We can start to [decipher them]… We can understand what their past has been like. We can understand how they function today. And then we can start to make projections about what is going to happen to these forests. Some of the early models project that these forests are going to want to move north and west.”

Steve Sillett with the simple tool used to extract samples from redwood trees. The corer is drilled into the tree by turning the blue handle over and over — often hundreds of feet up, suspended from climbing gear.

The grand idea

Save the Redwoods League, philanthropists and scientists from UC Berkeley and Humboldt State University have joined together in forming the Redwood and Climate Change Initiative. The idea is to collect a baseline of information using 16 sites throughout the coastal redwood and giant sequoia regions including here in Humboldt. Each site is carefully mapped and studied — not just at the ground level but each tree is mapped and drawn individually from their base to their crown, hundreds of feet in the air. The scientists are exploring these trees thoroughly.

These giants are not only mapped on the outside but they are mapped on the inside. Most people know that a tree adds rings each year. And they know that the width of the ring indicates the amount of water etc. that was available to the tree that year. In perfectly round trees taking samples is a matter of carefully hand drilling into and removing a very slender dowel from the base of the tree. The dowel offers a cross section of the rings within each specimen. But redwoods are not round trees at their base. Among their many eccentricities, they form buttresses and have what Steve Sillett, star of National Geographic’s Oct., 2009 cover story, The Tallest Trees, calls “all kinds of weird irregularities, fire scars and bumps.”

Up until now, determining how many rings a certain tree had was difficult and usually impossible. But Redwood and Climate Change Initiative’s Allyson Carroll worked with others on the team to devise a way to reach within each redwood and unlock its secrets. Sillet said, “Up until this project here, redwoods had never really been successfully cross dated… it [was]hard to be sure what year belonged to each ring… You can’t… with any confidence… know this is the year 1672 on that ring – it could be plus or minus 500 years depending on the tree. What Allison was able to do for the first time was cross date the redwood record because we had cores from all these heights.”

The sample cores’ rings are measured and the patterns of wide rings to narrow rings are entered numerically into computers which then compare samples from different heights in each tree and in different trees to accurately determine dates. The rings of the redwoods in different areas show a relationship to each other. According to Allyson Carroll, “There is some synchronicity throughout the whole range of redwoods.”

Not only can scientists begin to see climate across the region back through time but “We can reconstruct climate if we can correlate …the variation in ring width with past climate records.”

In addition, Anthony Ambrose – who received his masters at Humboldt State but now is a research scientist at Berkeley – knows there are even more secrets that can be determined from these trees. “There is a tremendous amount of information stored within each ring,” he explained. “As the wood gets produced in each ring, there is chemical signatures that get laid down with that wood at the same time – what we refer to as stable isotopes. By carefully taking the wood from each one of these little rings (once they’ve been cross dated), we know the exact year this particular ring was formed. We can then take that piece of wood and analyze it… we can… get a lot of information about the environmental conditions that were occurring at the time that that wood was being produced… For example, fog water has a particular isotopic signature…as opposed to rain water …”

Holding a device which stabilizes the thin cores extracted from redwoods, Allyson Carroll describes how the rings are exposed by sanding and then they are studied for their secrets.

The researchers then correlate the information in the rings with known climate conditions in our recent past. Then, according to Ambrose, they use those records in the past “to infer further back in time as far back as these tree rings go” –in some cases inferring climate conditions for thousands of years in the past. And they can do this fairly precisely. They have a tool called a micro mill that lets them take miniscule samples from within each ring allowing them to get a fairly precise understanding of how the trees were functioning and what their climate was like — not just yearly but also within each season!

The team is not just interested in the giant trees. The researchers gather cones at each site and sprout young trees. Professor Todd Dawson of UC Berkeley explains, “The seedlings are the gateway to the forest.” Members of the team raise the trees in controlled conditions and conduct tests. Dawson says, “We bring them into the greenhouse and in a very targeted way set up experiments where we can manipulate the climatic variables that we believe, and the climate models predict, are going to influence these trees in the future.”

Redwoods yield history

As the team worked together using all their different areas of expertise, one of the surprising pieces of information they discovered was that the redwoods are growing faster than they ever have before. Using the rings, the researchers can now tell how big a tree was at any given time in the past. And they can see, according to Sillett, “the rate of wood production is nearly twice as high as it was in 1900. We’re not sure why. We’re not sure what that means at the whole forest level. [But] these trees…are growing faster now than they have grown… ever.”

This doesn’t mean the trees are thriving though. They appear to be responding to increased carbon dioxide in the atmosphere. What the team doesn’t know is can the growth rate be sustained? Ambrose worries, “…[I]f temperatures continue to increase to a certain point to where they physiologically can’t tolerate that. Or if fog or rainwater decreases to a point that they become so water stressed that they can’t take advantage of that carbon dioxide, how sustainable [will that growth be?]” It is also possible that since fog has dropped over 30 percent in the last hundred years, increasing access to sunlight has sped up the trees’ growth. Or it could be a complex interaction of many factors. The team hopes to learn the answers to that over the next few years.

Todd Dawson demonstrates a wireless weather station developed to help the team monitor climate conditions not only on the forest floor but in the canopy as well.

With the new data, politicians and conservationists might better understand where redwood trees will best survive the climate changes and where their ranges might disappear. With information such as this, scarce conservation resources could be managed better. If, as Hartley suggested earlier, new climate models show the forests moving to the north and west, then park land can be purchased in areas targeted to most likely contain those future redwoods.

Looking for partners

The team has been gathering data for almost a year and plans to spend the next two years putting in systems that will allow them to gather even more. They plan to continue to monitor the stations that they have put in for years after that. The data they gather will help them understand how the redwoods are responding to climate change over time.

The researchers and the tools they need do not come cheap. The first three years alone are estimated to cost $2.5 million. Luckily, they have some supporters. Save the Redwoods League is, of course, helping to fund the operation. They have raised a quarter of a million dollars. The organization is receiving help as well. Several philanthropists have stepped forward. Kenneth Fisher, who formerly attended HSU as a forestry student and went on to become a financial advisor and author, has created a $500,000 matching grant. The team, scientists, conservationists and philanthropists are looking for interested partners to help them reach their goal of understanding the effects of climate change on our redwoods. Visit for more information.

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