Excerpted from The Cold Canyon Fire Journals: Green Shoots and Silver Linings in the Ashes, by Robin Lee Carlson. Published by Heyday, 2022. All rights reserved.In The Cold Canyon Fire Journals: Green Shoots and Silver Linings in the Ashes, artist and naturalist Robin Lee Carlson shares the six years she spent learning from the wildfires that burned through Stebbins Cold Canyon Reserve near Davis, California twice in five years. This excerpt, drawn from the chapter “The Relativity of Time,” explores the tree-entangled life that returns in abundance after fire—some of which emerges rapidly, and some of which takes longer to make itself known. “It is tempting to immediately tally the living and the dead,” notes Carlson. “But trees exist on a very different time scale, and their lives and deaths caution against hasty conclusions.”
Look at this burned bay laurel. Do you see the way those branches are all pointing the same direction?” Dead tree branches just over my head etch lines into the electric-blue sky, and I am transfixed. From the thicker supporting branches to the finest twigs, they all swirl in the same direction, performing a ghostly dance choreographed by the Wragg Fire’s fierce, hot wind.* Even though the air around me is completely still, I can easily envision the wind whipping around these trees as the fire blazed and they were frozen in this shape.
* Ignited when a car exhaust sparked dry grass near Napa County’s Lake Berryessa, the Wragg Fire burned some 8051 acres between July 22 and August 5, 2015.
It has been a year-and-a-half since the fire, and a participant in a field sketching class I am leading at Cold Canyon has just pointed out these shapes in the trees to me. Miriam Morrill is a biologist and a specialist in fire and communications at the Bureau of Land Management (BLM). She is also an artist, and I see that she has been making notes and drawings in her sketchbook that capture some of the signs of fire behavior still legible in the landscape. This is not a language that I know, and we are excited to compare notes.
She explains that she sees more trees and tree skeletons on Blue Ridge than she would expect had the fire advanced up that slope from the bottom of the canyon. She surmises that the fire instead came from the west, over the top of the ridge, and backed down into the canyon, burning less intensely moving downslope than it would have had it been charging upslope. I tell her that this is what I know to have been the case, based on Jeffrey Clary’s descriptions of the fire’s progress. Miriam says that she also notices that the branches of the leafless trees where we are standing near the creek are all pointing in different directions, as if different eddies of wind were whirling around each one. From this, Miriam concludes that the fire became more intense at the bottom of the canyon before racing up the slope on the other side. As the Wragg Fire paused here, the intensity of the fire created its own weather.
Strong winds gusted and eddied among the folds and pockets of the hills. Where the fire did not fully burn the vegetation, its heat dried out the branches. Losing their moisture made them permanently inflexible, pointing in the direction of the last wind they would ever feel. This phenomenon is termed foliage freeze. Time stopped, arrested, and I am held there too, caught in this still, quiet day but also in the midst of the roaring frenzy of fire and wind of late July 2015.
This could be the image of violence preserved, jarring me out of time on a peaceful day. I might see this as the life force of these trees sucked right out of them by the wind, with their macabre skeletons still here to remind me. If fire is only a catastrophe from which this ecosystem must recover, the brutality of that image is appropriate. But if fire’s place in the ecosystem is subtler, then those frozen branches might equally be seen as a reminder of the continuity that underlies the fire, tying the seemingly singular event to the past and future of the landscape.
Disturbance has a past and a future and blends more easily into both than it would seem. And now, as I stand here in the present, the frozen branches are important clues to the behavior of the fire. Fire leaves signs behind on the land that are often fleeting—erased by wind and rain and footsteps—so it feels like a race to find and read them before they disappear. Patterns of ash and char, curled leaves, fallen tree trunks, and grass stems—all are quickly obscured by the movement of animals, the fall of rain and rush of wind, and the growth of new vegetation. These twisted branches, though, remain. The fire’s passage is frozen in the trees’ bodies, and the trees’ writhing limbs marking this path are emblazoned on my mind.
Oaks: Anchors in time
Growing up in California’s Central Valley ensured that water worries indelibly marked my subconscious. I am a child of brown summers and green winters, of regular drought and water scarcity. I was a toddler during the 1976–77 drought and have vivid memories of my mother explaining to me why we couldn’t flush the toilet every time we used it. Even as a child, I approached each winter with concern: Will there be enough rain this year? Will the rivers dry up? I find nothing more reassuring than rain and nothing more terrifying than the endless cloudless summer skies.
As I got older, I began to understand the ways life here has adapted to make the most of the rain we do receive. I am reassured by the hardy species that get by on little water and conserve their moisture in ingenious ways, like the blue oaks standing tall in the woodlands and savannas that ring the Central Valley. These are important members of Cold Canyon habitats, the trees that Jeffrey was concerned about after the Wragg Fire. Blue oaks are of middling size for oaks, with the wildly crooking branches common among oaks that make their limbs look as though they are dancing ecstatically. Their leaves are compact, with only wavy margins, not the deep lobes of some of the other oak species. The waxiness of their leaves helps with moisture retention in their often-arid habitats.
Staunchly Californian, blue oaks are endemic here—found nowhere else in the world. They live at lower elevations in the Coast Ranges and the Sierra Nevada, as well as on the southern end of the Cascade and Klamath Mountains. A few grow in the Central Valley itself, but they mostly prefer to be up in the hills. Though I live in the flatlands of the valley, I am glad to be close to the hills and mountains, and it is to these foothill habitats that I turn for guidance in how to live in an often-parched land.
Of all the deciduous oaks in California, blue oaks are the most able to withstand drought. Their taproot—their main central root—can grow deep into the ground to find the water table, to depths of eighty feet, though they can also focus their energy on growing shallower roots if water is available higher in the soil. They need soil that is relatively dry and well drained, and are found on soils that are poorer in nitrogen, phosphorous, organic matter, and other nutrients than the soils that support other California oaks. On these soils, they cultivate communities of other hardy species by holding the earth in place against erosion and using their taproots to bring water to the surface, incidentally making it available to other species as well. Before introduced annual species came to dominate California grasslands and savannas, blue oaks grew alongside bunchgrasses such as blue wildrye and purple needlegrass, similarly water-conserving species. The oaks and grasses mutually supported one another, sharing resources via fungal mycelial networks.
Now, introduced annuals such as redstem filaree, cheatgrass, and wild oat have largely replaced the bunchgrasses. The introduced species compete with young oaks for space, water, and light, just as they outcompeted the native bunchgrasses for these resources. As in the rest of their range, blue oaks in Cold Canyon shelter quite a few introduced annual species, but they are also home and sustenance to many other creatures. Nuttall’s woodpeckers rely on them for foraging and nesting. Dusky-footed woodrats build at their feet and eat their acorns. Fallen branches are important gathering places for western fence lizards. Oak titmice—birds the soft mousy brown of their namesakes—defend year-round territories in their canopies.
It is easy to see the wildlife that depends on the oaks, but equally important to understand the less visible forces at work. Blue oaks are critical to the quality of the soil around them, increasing its nutrient content. This is thanks to the fall of leaf litter, which increases the nitrogen in the soil. It is also because trees capture moisture from the air that otherwise would have evaporated. Instead, the water droplets adhere to the leaves, eventually aggregate into larger drops and then fall to the ground. The drops bring along important nutrients—potassium, phosphorous, and magnesium, for example—that were present in the air and are concentrated when the drops form.
There are three kinds of oaks growing in Cold Canyon, two of which are trees—blue oak and interior live oak—and scrub oak, which takes a shrubbier form. Interior live oaks tend to be found in the bottoms of the canyons, as they prefer the wetter areas in the riparian zones, and these are often too wet for blue oaks. Blue oaks generally grow on the hillsides. The distinctions are not absolute: there are certainly blue oaks growing in the canyons and live oaks on the hills, but the general pattern holds.
Over the five years of my visits, when I look closely at oaks, I try to decipher the puzzle of their health and survival. In a landscape of rapidly sprouting annual plants and fast-growing shrubs, trees are not as easy to assess. There are no immediate answers to how the oaks at Cold Canyon are faring. In the areas closest to the creek, some oaks did not burn at all and are doing fine—these are mostly interior live oaks. A little further from the creek, there are more interior live oaks, and some of these burned. These that burned are sprouting, strong shoots growing up from their bases, from their root crowns. The brand-new leaves in their chartreuse skin are spiky and fresh. Further up the slopes, some of the blue oaks are sprouting. On the blue oaks I see, the sprouts are not at the bases of the trunks but higher on the tree, on the branches. These differences are characteristic of the two oak species: live oaks tend to regrow from their bases, blue oaks from their crowns.
The oaks that are able to survive fires will benefit from them, especially if the fires were low intensity. Fire removes accumulated litter beneath the trees, which helps reduce the numbers of insect pests that feed on acorns, such as filbert worms and filbert weevils, two of the most common in California. Fire also helps remove some of the oaks’ competitors for resources, such as annual grasses, though it can also open opportunities for other competitors—thistles, filaree, and the like—to gain a foothold and claim the open turf for themselves.
The world underneath the blue oaks’ canopy is much different now than it was before incursions of plowing, plants, and livestock. Fire can still be a healthy force, but that is no longer always the case, now that fires burn hotter and higher, and more often kill the crowns of trees, making it hard for trees to survive and resprout. The bark of mature blue oaks is thinner than other similar oaks, which increases the trees’ susceptibility to fire as they age. It is more difficult for acorns to grow under competition from introduced plants and in our rapidly drying environment, with droughts becoming more and more common.
All of this is to say that one year, three years, five years in, it is too early to tell how the oaks are doing at Cold Canyon. Trees challenge our impatient animal desire to know what is happening. Acorns take a very long time to make more acorns. Seedlings take a long time to become saplings, which take a long time to become mature trees. Time stopped for the branches frozen by the heat of the fire, but most of those trees are still alive and sprouting green at their bases. Trees live and die slowly, but it is difficult to remember this in the context of a disturbance like wildfire. The fire can feel like a catastrophe, and tallying the damage afterward feels so urgent. Trees move in their own time, and it is hard for me to comprehend when I am so quick, so mobile, so unrooted.
Oak gall wasps
Sometimes I go hunting for marvels, and sometimes they are sitting right in the middle of the trail, in shocking bright-pink glory. On a day when I arrive at Cold Canyon planning to focus on oak regrowth patterns, it is a strangely appropriate gift to find a crackly, dry blue oak leaf in front of me, covered in tiny galls. There two different kinds of gall on the leaf, both elaborately structured and very pink. I pick up the leaf and sit down on a rock beside the trail to wonder at the details of these tiny homes, nurseries to the microscopic babies within.
The interaction that creates these intricate structures is an amazing tale of manipulation, and a relationship maybe even more strange than the complex interaction fostered by horntails, fungi, and the distressed trees in which they lay their eggs.* Once again, it is wasps that are responsible. This time, very much unlike the large, somewhat alarming horntails, however, gall wasps are no bigger than about a quarter of an inch. Some of the smallest gall wasps in the world are only one millimeter long, the size of a comma on this page.
* In Chapter Two, “First Responders,” Carlson describes how horntail wasps (family Siricidae) are some of the first insects to arrive after a fire, drawn to the distressed trees in which they will deposit their eggs—along with symbiotic fungi that break down the wood upon which their larvae will feed.
Trees move in their own time, and it is hard for me to comprehend when I am so quick, so mobile, so unrooted.
Female gall wasps lay their eggs in rapidly growing parts of trees, such as twigs or leaves like the one I am holding in my hand. Once the eggs hatch and the wasp larvae begin to eat the plant tissue, a chemical in their saliva, or perhaps the mechanical process of their feeding itself, stimulates the plant to redirect some of its own cells to produce a protective outer structure that surrounds the larvae. This is a defense response by the plant, sequestering the larvae so that they do not eat its other parts. But it has great benefits for the larvae as well. The gall is both shelter and, inside, more food for the ravenous larvae, which comfortably feed until they mature and chew their way out of the nursery as adults. It does not seem as though the wasps do any real harm to their host plants, though they do of course consume some resources that would otherwise be used to meet the plants’ own needs.
What is most amazing, and apparent even on the leaf I’ve just found, is that each species of gall wasp stimulates a very specific and unique structure of gall. One of the kinds of gall on the leaf has spines sticking out in all direction. This is the home of a batch of urchin gall wasp larvae. The other kind is almost furry, and is made by crystalline gall wasps. The gall shapes are even expressed in the wasps’ scientific names. The urchin gall wasp is Cynips quercusechinus—the species name means “oak hedgehog,” emphasizing its spikes. The crystalline gall wasp is Andricus crystallinus, inspired by the delicacy and translucence of its fine “hairs.” Two different species, with two characteristic gall shapes. And there are over a hundred different gall wasps known so far worldwide. How on earth do the chemicals in the saliva of the larvae dictate the shape of the gall that the plant cells will build?
Most gall wasps are specific to a single type of tree, usually an oak. It turns out that blue oaks have the largest known number of different gall wasp species, at forty-one and counting. They also appear to have the greatest diversity of shape and color of galls. I am looking at the galls just a little after one year since the fire. I try to guess which of the blue oaks around me dropped this leaf. I wonder whether it was a tree that burned, and this was a new leaf since the fire, or one that survived the fire intact. Perhaps the wasps whose offspring were reared in these galls came to Cold Canyon after the fire, or perhaps they survived the fire as larvae themselves.
The effects of fire on oak galls have not been extensively studied, but it appears that gall wasps need time after a fire to return. There must be oaks for them to return to, either newly grown oaks or ones that survived the fire. There must be sources near the burn for them to come from. And some wasp larvae surely survive the fire, sheltering in the oaks that did not burn and remained cool enough that their leaves were not all killed by the heat. Adult wasps are not likely to survive the fire themselves, but then, they generally live only about a week, so the wasp truly spends most of its life—about a year—as a larva.
How funny it is that wasps have twice been my windows into the endlessly intricate webs of interactions that compose these ecosystems. First, the horntails, who rush to burned trees to lay their eggs and inject their symbiotic fungi. Now the gall wasps, who bend the oaks to their will but are dependent on their hosts for shelter and protection when the world around them burns. Without being present in these places—burning and burned—I would have remained ignorant of these beautiful mysteries. The wasps’ relationships are just glimpses into vast silken webs of stories that humans have not yet even dreamed. Start traveling along just one exposed thread, and how many more nodes in the silk might we find? The ones we do see tantalize us with the many that are yet unknown.
Gray pines: waves of loss and return
Gray pines, towering over the other trees at Cold Canyon, seem to me the embodiment of solidity and permanence after the fire. They have an underappreciated beauty, being arguably rather spindly and dull in comparison with some of the more majestic pine species. But I think their long, pale-green needles are pretty, especially in the bright summer sun. And while their needles are not densely packed enough to create a whole lot of shade, I find they create striking silhouettes against wintery overcast skies. In the early years after the canyon burned, I am anxious to count the survivors and the lost, to take inventory, even if anecdotal, of the fire’s casualties. Studying the gray pines, I can see green needles on what look like two-thirds of them, so I assume they have survived fairly well. But on a winter hike with Jeffrey Clary and Sarah Oktay, the Reserve’s current director, just over three years after the fire, I learn that the truth is likely more complicated.
Gray pines, also known as foothill pines, are often found in the blue oak woodlands and savannas that are interspersed with chaparral habitats in the California foothills. Like blue oaks and chaparral shrubs, they are hardy and thrive in places with drier climates and less nutrient-rich soils. Unlike many other plants, they do not have root, trunk, or bark adaptations that allow them to survive fire. Gray pines are extremely pitchy, even for a pine. They are torches in a fire, thanks to the resin in their needles, cones, bark, and wood. Because they do not contain the burls or other root structures that allow many chaparral shrubs to regrow, a gray pine too damaged by fire will not grow back.
Instead, gray pines must start all over again, growing from the seeds protected inside their enormous, spiny cones. I see cones, open and dry, with seeds long spilled, all over the canyon. Picking them up and turning them in my hands, I wonder whether their seeds are unfurling now, nestled underground where they landed after dispersing when the cone opened still high on its tree. The heat of fire stimulates germination by weakening or breaking the seed’s coat and allowing it to begin development. Gray pine seeds are also able to germinate without fire, but there are other pine species, such as lodgepole and knobcone, that do require fire for germination, at least in some parts of their ranges.
A gray pine too damaged by fire will not grow back.
This all sounds reasonably straightforward: gray pines mostly die in fires and eventually return to the landscape as new sprouts. It is the timing of their dying that is a surprise. Jeffrey points out that even though many of the trees at Cold Canyon still have green needles in their crowns, they may already have been killed by the fire, either because part or all of them burned or because the heat of the fire was too great and killed their tissues. Set inexorably onto the path to their fate, they are continuing to function while slowly winding down. In their diminishment, they are now home to organisms that they would have easily fought off while healthy. The fire drew pine sawyer beetles—a kind of longhorn beetle—and their larvae are now tunneling through the pines’ wood. Bark beetles, such as pine engravers, will also have come, finding nourishment in the wood of the dying trees.
These wood-boring beetles and their relatives are usually healthy members of forest communities, consuming only trees that are already dead or dying and returning the trees’ nutrients to the ecosystem. But in the increasingly stressed habitats of the western US, some species, such as the pine engravers, have become decidedly unhealthy. In the face of plentiful dead wood during years of drought and fire and excessive logging, the beetle populations explode. Voracious new generations feast on living trees too, making for even more fuel in wildfires and escalating the vicious cycle. While we are most familiar with large expanses of dead pines and firs in the Sierra, gray pines are not immune to these amplifying effects of climate and beetle. As I walk beneath a pine with silvery-green needles left on only a few of its higher branches, I see the fine line between health and disease, between beetles as beneficial recyclers and beetles as forest destroyers.
I am learning that dying is a completely different phenomenon for a tree than for all of us more ephemeral creatures. It is not a single event in time but a very long process. How smooth is the continuum of living and dying and how hard to say where some organisms are on that spectrum.* There are no quick answers in assessing the results of upheavals like wildfire, at least for trees, as I watch the aftermath play out slowly over the years.
* For more on how trees blend of life and death, see Peter Del Tredici, “The Roots of Rejuvenation,” in this issue.
Gray pines are common in chaparral habitats, but they require plenty of time to recolonize between wildfires, after the fires have mostly killed off the existing trees. On the one hand, if wildfires occur too frequently in chaparral, there will not be enough time for new gray pines to grow from seed. As the window for recolonizing closes, gray pines will slowly disappear from these habitats. On the other hand, if fire is completely absent from the chaparral ecosystem, gray pines will take over—enough gray pines will eventually colonize that the blue oaks cannot compete for space and sunlight. Fire—at least a healthy fire regime—keeps the balance in these blue oak and gray pine foothill habitats.
After my hike with Jeffrey and Sarah, before I head home to the valley flatlands, I stand next to a gray pine and put my hand on its bark. Time slows to a crawl as I deliberately calm my quick animal breaths. Time stops while I try to think in tree time. Here time is measured in roots creeping, tunneling, and connecting with fungal mycelia and other roots. Time passes in rings of wood expanding, thickening, drying, and cracking into bark. And time is the slow, slow pull of senescence, embarked on long before the tree’s final end. Senescence is set to the tiny music of the jaws of beetle larvae scraping and gnawing their intricate way through the tree, just below the surface of the bark.
This is a kind of sorrow, deep and abiding. There is nothing that will stop the onward pull of time and the tightening of death’s grip. The last green needles will brown. The wood will fully dry. The tree will continue to stand for a long time, entirely dead, waiting for the gust of wind or shift of soil that will send it crashing to the ground. But I am also, just as deeply, moved by the cycles in which the pines and I are enveloped. As though my awareness of the process allows me into the rolling pattern. Nothing is what it once was, nothing in the view ahead of me can stay this way forever, and we are all senescing even as we are full of life.
The gall wasps whose tiny homes I marvel at on blue oak leaves live only a week as adults. A blink of an eye. What would they make of my ponderously long and slow life, beyond the limits of comprehension? Just as I struggle to understand how a living tree can also already be dead.
Robin Lee Carlson is a natural science writer and illustrator based in Davis, California. Visit her website at robinleecarlson.com
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