Big Trees, and a Field Trip

A Tale of Big Tree Hunting In California

Disclaimer: I wrote this in 1999. Many of the record trees discussed here have since been supplanted by other trees, or have died. I have updated the first three sections, though, to maintain a currently-relevant discussion of how big trees are measured.

It's the middle of July and Seattle is heading into another day of a record heat wave as I board the jet for Sacramanto. I'm going to be spending the next five days with Dr. Robert Van Pelt, as he is known these days, AKA Big Tree Bob. His nickname is a simple one: Bob is the leading exponent in this country of the search for and documentation of the biggest trees. He was long one of the most enthusiastic contributors to the Big Tree Register maintained by the American Forestry Association, which records the size and location of the biggest known individual of every tree species native or naturalized in the continental United States. In more recent years his purview has grown, and he now tracks records of the biggest trees known throughout the world, with a special and personal emphasis on the giant trees of western North America--species such as the giant sequoia, the coast redwood, the Sitka spruce and their kin, including many of the largest tree species known. For some of these species, he has found the largest known specimens. For the rest, he knows the trees, who found them, and much besides.

The Bigness of Trees

Since the American Forestry Association established the Big Tree Registry in 1948, the biggest tree has been the one with the most "points," points being assigned as the sum of the tree's girth in inches (measured at breast height, 1.37 metres), its height in feet, and the mean diameter of its crown in feet. This is an artificial system and is often criticized as such, but it has survived because it is a simple system and is fairly free of ambiguity. Most scientists I have spoken with about this think that another system might be better, but a system that truly states a tree's bigness would have to be based on something like total plant biomass, total living biomass, total wood volume, or a similar variable that in practice is extremely difficult to measure. In recent years, Bob and various other lovers of big trees have chosen to reduce their use of the point system and are now defining big trees on the basis of a variable that presumably provides a more accurate estimate of actual tree size, namely stem volume. Stem volume is more difficult to measure than points. It requires a tree of relatively simple architecture (i.e., a single straight stem). Fortunately, this is the typical architecture of most conifers (at least, most of the Pinaceae, Cupressaceae and Araucariaceae). Given such a tree, the surveyor then determines the tree's precise diameter at various heights above the ground and uses a computer to perform the necessary volume calculations. The biggest problem with this method is that it requires determining tree diameter at various heights, and this in turn requires either climbing the tree or performing what was hitherto a highly precise and time-consuming piece of survey work. However, the 21st Century has given us laser transits that immensely simplify the process, and these days collecting the necessary measurements only requires an hour or two of work, provided that you have access to a laser transit (they are costly) and that you can get to the tree, which can be an adventure in itself. Lasers have also immensely simplified the problem of determining a tree's height. These days, most people who are seriously interested in getting an accurate tree height use a laser rangefinder; models sufficient for 10 cm accuracy can be acquired for a few hundred dollars, and the best equipment allows accuracy of less than a centimeter. With such equipment, a tree's height can now be determined to within a few decimeters in the space of ten seconds or so, and one person can now do in a day what previously would have occupied a team for a period of weeks.

Digression: Lasers

Stem volume is estimated without additions for roots or branches and no substraction for scars or cavities. To calculate stem volume, you use a laser transit to determine stem diameter on two perpendicular axes at many points along the trunk, and then calculate the volume of the stack of closed conic prisms so generated.

For this trip, bob has the use of two lasers. One is the Impulse. This is about the size and weight of a small video camera and costs $2,500 at this time, although prices are expected to fall for several years yet. It contains an infrared laser, a digital clinometer, and a microprocessor, and is surmounted by a telescopic sight. You point it at the topmost twig of a tree, press a button, and it will tell you the distance to that twig, the horizontal distance to the tree, or the vertical offset to the twig. If you then shoot the base of the tree, it will also tell you the vertical difference between the base of the tree and its top, i.e. its height. In the hands of a practiced user, it is reasonable to check four or five trees per minute.

Note that the phrase "topmost twig of a tree" is deceptively simple. Traditional trigonometric methods of determining tree height (employing either the Hypsinometer to calculate heights by similar triangles or the tape and clinometer to calculate by numerical trigonometry) always overestimate true height because they are based on the assumption that the topmost twig lies directly above the base. In practice, nearly all trees have a lean angle, and lower twigs usually appear higher because they are in the foreground, i.e. they are located on an azimuth oriented towards the observer. Using an analog transit (the old method), the only way this could be determined is by performing highly accurate measurements from at least two vantage points, preferably located on azimuths (relative to the stem) located perpendicular to each other. Almost nobody ever did this (Wendell Flint, discussed below, is one of only two exceptions I know of). With a laser, however, the user can quickly check several different twigs in the crown and determine which one is actually highest, irrespective of distance from the user.

The second laser in Bob's pack is the Criterion. This is about the size and weight of a red brick and requires an external battery pack. To get really precise readings, it must be mounted on a tripod, but it can be handheld for reconnaissance work. It will calculate heights just like the Impulse, except that its clinometer only works at angles of less than 60°. It will also measure azimuthal angles and ranges, meaning that it can directly measure the diameter of a tree at any height off the ground, reading out both height and diameter. Consequently, this instrument allows volume measurements. Such measurements are relatively simple if you're measuring a monopodial (single-stemmed) tree. For trees with multiple tops, the problem is much more complex, and for trees with truly complex canopy structure, such as most hardwoods, volume measurement becomes impractical (or at least, extremely time-consuming).

There is a third laser that Michael owns and that just about anyone can buy for a few hundred dollars. This is the Lightspeed. It is less accurate than the others and does not include a clinometer, but it will still provide you with the length of the baseline and the hypotenuse of the triangle used to calculate tree heights, and as such is far easier to use and more accurate than any other trigonometric method of measuring tree heights. When the Criterion isn't around, these guys use the Lightspeed to measure heights and they determine tree diameters by actually climbing the tree and wrapping a tape around it at various heights above the ground. In this way they have measured stem volumes on many large redwoods.

The last truly reliable way of measuring tree heights is by climbing to the very top of the tree and stretching a measuring tape to the ground (this method is called "tape drop"). These guys have done that fairly often, as well.

What makes a tree big?

Bob has a nearly photographic memory where big tree data are concerned. The largest of all, a giant sequoia (Sequoiadendron giganteum), is 55,040 cubic feet, followed closely by the largest Coast redwood (Sequoia sempervirens) at 36,890 cubic feet. The largest sugar pine (Pinus lambertiana) is 8,990 cubic feet (for some reason Bob shuns the Metric system for big tree statistics, though in his professional life he uses it exclusively). The reason why sugar pines are the biggest pines is because they have very little taper. They shoot up out of the ground like almost perfect cylinders, sometimes with all of their crown in the top 20% or so of the tree. For all tree species, the key to achieving high wood volume is a big diameter, sustained to great height. Sugar pines are very good at this, whereas ponderosa pine (Pinus ponderosa), for instance, usually has a deep crown and pronounced taper. For the vast majority of what are commonly thought of as big conifers, 5,000 cubic feet would impress most people as a truly enormous tree, although the very largest trees ever known had volumes up to ten times that.

Ready For Action

I ponder this and other aspects of the big tree world while I wait for Bob at the airport, and in time he arrives, hot off the highway from Eureka in his Toyota minivan with the "BIGTREEZ" license plate. He's not alone. With him are three big tree hunters from Eureka, Scott, Steve and Michael; and enough extra space to barely squeeze in me and my pack. I pile in and we head for the hills. We are bound for Calaveras Big Trees State Park, site of the northernmost big groves of giant sequoia and home range for the largest pine trees in the world.

The drive takes a couple of hours, and as we drive along Bob obligingly identifies every tree along the way, particularly noting the large ones. He's the most accomplished dendrologist I've ever met, a man who seems able to identify any tree at a glance, whatever its native land. I wonder how he would fare in a place like northern Queensland, where there might be 500 species on a hectare, and I conclude he would likely remember each species from a moment's acquaintance. I have known botanists who are like that with mosses or grasses; Bob is their equivalent with trees. He knows each one personally, and remembers it.

As we drive along, talk in the car is predictably about trees, especially the biggest, especially the biggest redwoods. The Coast Redwood seems to be the staff of life for each of the three gentlemen from Eureka. Steve Sillett shows this most clearly, perhaps; he is an assistant professor at Humboldt State University, a few years out of his doctorate, and his research focuses on the canopy of the temperate rainforest. He climbs these trees for love of them, but also to conduct research in them. He is one of the most experienced of the big tree climbers. He has hauled National Geographic photographers into the tops of the loftiest redwoods and sequoias, and has been the finder and climber of several of the tallest redwoods. He has also done much to develop and hone the art of technical tree climbing. He has done much of this work with Scott. Scott, for his part, simply loves to climb big redwoods. He wants to do a master's thesis under Steve, focusing on some kind of canopy research. He doesn't seem overly concerned about what specific research topic he might pursue; the main requirement is that it involve a great deal of tree climbing. He rather reminds me of the rock climbers I used to hang out with -- to climb is the thing; the rest of life is there to provide the food, sleep and equipment purchases that make climbing possible. But of the three, the most passionate seems to be Michael Taylor. Michael's passion is the coast redwood, and to it he is utterly devoted. Bob tells me Michael has discovered (or co-discovered) 21 of the 23 tallest trees, as well as having found all redwoods with a stem volume of more than 30,000 cubic feet. He seems to spend every spare moment in the bush, climbing and measuring known trees or penetrating the most remote fastnesses of the redwood's home forest to find the tallest and largest among them. Most recently he found the DNT, the Del Norte Titan, largest known coast redwood and over 300 feet tall. The four of them have just returned from measuring it with the laser, confirming its size, at 36,890 cubic feet larger than any tree on earth except a handful of giant sequoias. It grows a few meters from the Lost Monarch, another newly-discovered giant redwood, also one of the largest trees known; and in the same California park, a newly-discovered Douglas-fir, one of the largest of its species. All four of them are flying high, euphoric on this past week's orgy of giant tree discoveries, and ready for more.

We get to Calaveras Big Trees State Park in the evening and pull into a reserved site at the Oak Hollow campground, in the mixed conifer forest. In our campsite are sugar pine, incense-cedar and white fir (Abies concolor). Nearby, there are California black oak and ponderosa pine. The park has two sequoia groves, the North and South Groves. The North Grove is rather small, but it's the most-visited of all sequoia groves. The first sequoia found, the Discovery Tree, is there. The Mother of the Forest is there, a sequoia that was debarked and the bark shipped east to some Worlds Fair (a common fate for sequoias in the late 19th Century, when they were being logged with abandon). The snag of the Mother subsequently burned, but is still an imposing pillar of black wood. The South Grove is much more extensive, covering about two square miles. That's where we hope to find some really tall trees, over 300 feet.

The objective this trip is, of course, big trees. The biggest sugar pine grows near here. We hope to find a bigger and a taller one. We also hope to find the tallest giant sequoia here. The first plan, though, is to eat. We locate a nearby brewpub, with decent food that largely gets ignored as the talk runs on about big trees. We leave as soon as we're done and head back to camp, stopping off in the dark to look at the Discovery Tree. The Discovery Tree tonight is a very large stump, almost 8 metres across, and Bob tells us its tale. The Discovery tree was one of the first truly giant sequoia ever found (the first discovery, in 1833, was by the Walker party as they struggled through the Sierra north of the Yosemite valley ... they certainly passed through either the Merced or Toulumne groves, but their discovery never became widely known (Stephenson 2002)). It was discovered in 1852 by a prospector who was out hunting for some dinner. It is said that when he found this tree, he knew that no one at camp would believe him, so he went back and told them he had found gold. That easily produced the necessary witnesses. It is an apt comment on the pioneer spirit that soon after, this became the first really big sequoia to be cut down. There were no saws large enough to handle the job, so it was cut by drilling scores of parallel auger holes through the tree. Between the fallen trunk of the Discovery Tree and its stump has since grown a four-foot diameter sugar pine, which gives you an idea of how productive the soils are in this area. The fallen trunk is still there, the auger lines readily visible. Perhaps not surprisingly, the fallen tree was not turned into lumber; it was killed simply to prove that it could be killed. As John Muir later observed, "Great trees and groves used to be venerated as sacred monuments and halls of council and worship. But soon after the discovery of the Calaveras Grove one of the grandest trees was cut down for the sake of a stump! The laborious vandals had seen 'the biggest tree in the world ,' then, forsooth, they must try to see the biggest stump and dance on it" (Muir 1901). The Calaveras grove was owned by a lumber company for many years, and several of its grandest trees were logged, primarily for use in exhibitions and World Fairs. In 1909 the land was finally set aside as the Calaveras Bigtree National Forest.

Back at camp, Scott and Steve hang their Tree Boats. These are aluminum-framed nylon hammocks specifically designed for sleeping in the tops of big trees. Insulated blankets hang beneath to keep you from losing heat to the cold air, while an optional fly hangs overhead to keep the rain off. The carrying sack provides a bedside table of sorts. They are said to be quite comfortable to sleep in. Steve and Scott need them in order to fulfill their desire to spend the maximum possible amount of time in the tops of very tall trees.

We lounge around the campfire, absorbing beer and stories. Our talk skips merrily around the West as we talk over big trees (and big tree hunters) known, remembered, fallen, or still only hoped-for:

Bob - I've been looking up old champions. There's been about a dozen ponderosa pine champions in the last 30 years, and they've all been outpointed. They didn't die or anything. One of them is actually number one in terms of wood volume. Just south of Yosemite. A really impressive tree.

Michael - We've been doing some serious trailblazing in Jed Smith (State Park, California), penetrating deep into its interior.

Steve Sillett - We found a 357-footer in Jed Smith.

Scott - Wouldn't Randy Stoltmann be amazed at how so many giant trees have been found?

[Randy was British Columbia's leading big tree man. He died in 1994, in a backcountry skiing accident.]

Bob - He would be in heaven, just like we are. In fact, he would have probably broken those redcedar records by now, because redcedar was far and away his favorite tree. He was obsessed with it. In fact, he did a 3-dimensional carving, about this tall, of the Nolan Creek cedar, with all of its reiterations [multiple leaders]. It was so cool.

Scott - Has anybody taken over his place in British Columbia?

Bob - No. I spent a week up there last year. I'm going up there this year too. Most of the trees I have seen or know how to get to. A couple of them were nominated by Adrian Dorst, a photographer, and he knows where they are. But there's still a couple that I don't know about. Randy basically was the entire BC program. No one else has taken it up.

Steve Foster - You know, in Mexico City, they just set aside three million dollars to plant trees, and then they said well wait a minute, lets take care of the trees we already have.

Bob - Mexico City has some of the largest Taxodiums.

Chris - The Taxodiums in Chapultepec Park are supposed to be the largest planted trees in the world.

Bob - Yeah, those are the ones I'm talking about. Not much smaller than the El Tule tree.

Steve Foster - The Kalaloch cedar is amazing. How old do you think that tree is?

Bob - Its probably older than me. I just guess 2,000 on those. I think its a conservative estimate, but there's no possible way to tell.

Steve Foster - Where's the Marble Mountains?

Bob - Its just east of Jedediah Smith, just south of the Siskiyous. There's an incense-cedar there, 7,700 cubic feet, the next biggest tree after sugar pine. They grow in north-facing cirques up in those old mountains. That's where all the big incense-cedars are.

Michael - Is this area [Calaveras] well protected from wind and stuff, or is it just the great soil quality?

Bob - It's a pretty big park, and its down in a hole. All the private land, you notice, is not clearcut. Its all selectively logged, so there is some buffering of the wind.

Scott - How well has the area been surveyed?

Bob - Not well. Its been reconned, and some 10-footers have been measured. But in terms of heights, I don't know of anybody's measurements. What I hope we're going to do tomorrow is, we're supposed to meet those guys right here, and look for tall sequoias. Before the end of the day, though, I think we should take everyone and go check out the two record sugar pines. They're are only a few miles from here, and you guys can see how big the world's largest pine is.

The largest known sugar pine, at a Girl Scout camp in Dorrington, California.

A Day in the Field

This morning Dwight Willard shows up bright and early. He's author of a book about all the sequoia groves, and he brings a map about 25 years old that shows the location of every big sequoia in Calaveras. He also has data sheets recounting the trees' measurements as taken when first mapped in 1922 and again when the inventory was completed, around 1945. This is a gold mine of information and we quickly ascertain which trees are said to be the tallest in the park--two of them more than 300 feet! Excitement runs high that this morning will yield the tallest giant sequoia yet found. A few minutes later Wendell Flint arrives. Wendell is 79 years old, the grand old man of tree-volume measurement, a wiry silver-haired gentleman in a porkpie hat with a goatee. He and Bob are instantly engrossed in talk about big sequoias, big redwoods, big pines and their respective measurements and methods of stem volume.

Well, we launched forth into a busy day. We walked through the South Grove and saw many big sequoias, but none set any records. We measured the heights on several hundred trees and the tallest two were 281 feet. One was 280 and a bunch of others were 275-279. It certainly appears that there's a physiological limit on tree height in this area, since these trees were on sites that rarely if ever experience drought. It was a similar story for sugar pine heights; the tallest was 252 feet, but there were about 20 trees that topped 235 feet. At least we got to stroll through a gorgeous forest with lots of big sequoias. After the South Grove, we went to see the largest pine tree in the world. It's in a Girl Scout camp in Dorrington -- you can see it from the general store. It's stem volume is about 9,000 cubic feet; it looks almost like a small sequoia. The diameter is about 11 feet. The Girl Scout camp director chased us away, though. She thought we might pose a distraction (perhaps we would tell tall tales). We then drove into a private forest area above the Middle Fork Stanislaus River, and here we saw the official champion sugar pine (i.e., the one with the most 'points'). It is falsely listed as 232 feet tall (the lasers pinpointed it at 208 feet), and it has about a 12-foot dbh because it's on stilt roots. The whole base of the tree has been burned out by past fires and it stands perched on three remaining legs. It's still quite an impressive tree; Bob measured it at about 7,100 cubic feet, making it the second-biggest pine in the world.

Day Two

Today we hiked through the North Grove with Wendell. We measured the height of almost every sequoia there, and the tallest was 283 feet. That would be the tallest sequoia in the park. A small part of the grove has a sequoia overstory with a yew (Taxus brevifolia) understory. I believe this is a unique situation, since this is the southernmost occurrence of western yew and is close to the northern limit of sequoia. The yew forms a fairly continuous subcanopy in a small part of the grove, with yew heights up to 8 m (mostly 5 m).

After the walk, we all bought copies of Wendell's book, To Find the Biggest Tree, and got him to autograph them before he headed homeward. We then went to the part of the park that was formerly set aside as the Calaverals Bigtrees National Forest, looking for big sugar pines. The biggest we found was one that Bob had heard about previously. It had a diameter of about 10 feet, quickly narrowing to 9 feet and then nearly columnar to the base of the live crown, which had a depth of less than 10% of the tree's height. Based on the Criterion laser measurements, we estimate its volume at 6,600 cubic feet, which will make it the third largest sugar pine. Bob calls it the Calaveras Colossus. It was growing in a lovely forest where they have conducted an exemplary prescribed burning program. It was perhaps the only time I've ever seen a Sierra forest with a healthy fire regime, and with pine seedlings to prove it [although I'm told Yosemite National Park has an even more ecologically intelligent program]. By and large, though, it wasn't a great place to find big trees. Most of the forest was subject to potentially high drought stress, being located on the flanks or top of a ridge. Most of the trees were about 200 feet tall, which is a respectable height for a pine tree, but is scarcely superlative.

It had been a hot, sweaty and dirty day, so we went back to camp for showers and then into town for dinner at the brewpub. Bob felt that we've now used up our options for finding big trees, and the current plan is to drive south to Yosemite and pursue a rumor of the tallest known sugar pine. He's looked for it twice before and not yet found it, but he wants to try again and get detailed measurements on it.

Day Three

Today we first visited the site of a former champion Jeffrey pine up near Sonora Pass. We found it and it looks like it died just about the time it was first found, 30 years ago. It was in quite an advanced state of decay--we found it hard to believe that it could have reached that state on 30 years--but it was in the right place, the right size and had the big forked top in its description, and nothing anything like it for size is now growing anywhere near there. It was a monster pine, though. From there we drove to Yosemite and went looking for this former champion sugar pine that was supposed to be 270 feet tall. It was only a champion for one year. We think we found it too, and it appears to have only been dead for a couple of years--it still has fine twigs on it, and besides it reportedly was seen alive in 1995. But, dead it is, and so now I suppose the title of tallest sugar pine is up for grabs. After that, we hiked down to the Tuolumne grove, again in hopes of finding a record tall sequoia. Its trees are neither particularly tall nor particularly large as giant sequoias go, though it is an attractive grove in a pleasing hillside setting. The tallest was 279 feet, giving further evidence for the notion that there's a physiological barrier at 280 feet that perhaps is only broken due to genetic variability, which has produced at least one 295 foot tree down in the Giant Forest area.

Epilogue

Well, Michael persisted in the Quest, and in October we received news that in the Redwood Mountain Grove, Kings Canyon National Park, he had found two sequoias 305 and 307 feet tall, lasered with the Impulse -- the first confirmed sequoias more than 300 feet tall, and now the tallest known. In December, Bob and I traveled to Vancouver Island to see, measure and photograph the Red Creek fir, largest known Douglas-fir and thus the largest known member of the Pinaceae; to find and measure one of the three largest Sitka spruces; and to locate a couple of extraordinarily large cedars, in the Pacific Rim National Park area. All of this seeking after big wood does have a purpose apart from adventure and exploration; Bob is writing a book -- sequel to his Champion Trees of Washington State -- tentatively titled Forest Giants of Western North America, describing a hundred or so trees representing the twenty largest species of conifers in North America.

Citations

Muir, John. 1901. Our National Parks. Boston: Houghton Mifflin. 371p. Available online at the Library of Congress website "The Evolution of the Conservation Movement, 1850-1920," URL=http://memory.loc.gov/ammem/amrvhtml/conshome.html (accessed 1999.05.05).

Stephenson, Nathan L. 2002.03.04. Researcher, USGS. E-mail to John Lockhart, Sequoia Natural History Assoc.

Williams, Richard L. 1976. The Loggers. New York: Time-Life Books. 240p.