Desert rain

Posted by Chris Clarke on October 21, 2009

This is a first draft of chapter three of the J Tree book, to be read tonight at the Writers Group. Again, like previous chapters, it won’t be here forever, but I thought I’d maximize the feedback possibilities in this new age of open-source writing.

Chapter one is here. Chapter two is here. Both will be coming down in a week or so.

Desert Rain

The desert smells different after a rain. Even two sunny days later, groaning awake in the morning as the shadow of Kessler Peak shrinks eastward toward the mountain’s base and I am bathed in premature sunlight, the smell of wet soil an inch or two below the surface of the earth will fumigate my waking mind. It is an insistent scent, all the more notable for its usual absence.

It pervades my sleep and I dream of water.

In winter, one storm after another rises above the Pacific Ocean, hurls itself at the coast of California. One storm after another gets caught up in the mountains, scraped near-dry and released into the desert. A few get through still sopping.

From the top of Cima Dome I watch the winter storms approach through the open canopy of the Joshua tree forest. Each approaching storm casts a shadow on the landscape beneath it, blurs the horizon beyond as it fills the air with rain. I watch each shades pass over the distant mountains: the Soda and Avawatz mountains south of Death Valley, the New York and Providence Ranges off to the south. Each range loses its color as the storm settles in. Red and variegated slate and pale limestone white turn uniform dark, brooding.

Each approaching storm is fronted by a stiff, chill wind. The temperature drops a few degrees. I shiver against the front even though the sun still shines, even before the first drops fall.

The desert is on edge. Everything in it is primed to drink the rain: the Joshua trees, the shrubs and herbaceous plants seem to strain their leaves toward the passing clouds. The ravens and coyotes pant in anticipation. The tortoises wait and watch, heads peering from holes in the cutbanks along the wash.

The rain begins.

First come the big, fat drops, tentative at first, and widely spaced. They shine on the tips of Joshua tree leaves, on the exposed rock and the hood of my pickup, refracting sunlight filtered through interrupted clouds. One drop lands almost atop a colony of red and black ants. I watch the workers drink, a ring of quivering antennae a setting for a gleaming raindrop cabochon.

Then the rain gets serious. It falls in rolling staccato bursts upon the desert. What had been a broad constellation of raindrops on the soil spreads, merges into a solid sodden sheet of wet. Sage sparrows and cactus wrens that had been flitting from shrub to shrub retreat to the branches of the Joshua trees to wait out the storm.

All around me the desert relaxes, a shift so subtle I’m not sure whether I’m imagining it. At last! The rain. The earth, the trees, the rocks seem almost to slurp at the puddles. The top inch of soil is saturated quickly. Water begins to run off toward the nearest wash.

In a crook of the wash near my campsite, a cholla stem sticks awkwardly up out of moist sand. Above it, at the edge of a foot-high cutbank, its parent cactus seems to teeter warily. The next good storm may undermine it, send it tumbling down into the wash atop the branch it had dropped, there to send new thirsty roots into the sand and gravel. For now it stands, its profusion of wicked silver spines a gloriole backlit by rising sun. The dropped cholla branch has rooted. It strains debris from the passing flood.

Off to the west the sun shines on the Soda Mountains again. They gleam as if newly washed, shining through the trailing edge of the storm. Soon the rain will slacken, will end, and the sage sparrows will emerge from the Joshua tree branches to drink rainwater from the hollows in the rock.

Beneath the cholla in the wash a small pebble moves to one side, dislodged by something pushing up from underneath. A green needle emerges from the sand. Over the next several hours it will grow to a length of an inch or so. It is pale, translucent at first, offering little resistance to the light of the sun. Little resistance, but not none. Some of that light gets caught up in that green spear, where it is yoked to the plant’s metabolic machinery and put to work. The spear captures light and air and the scant moisture it has purloined from the sand. It transmutes sun and breezes and water into sweetness, sends sugar down its stem to feed its delving root. After a week or two another spear emerges, stouter and darker than the first, and a bit flatter. In time a third thin leaf comes up between the other two, and then a fourth.

•••

The Mojave averages less than five inches of precipitation each year. Averages are abstractions. They can be deceptive. In Bagdad, a desolate station on the Southern Pacific railroad line about fifty miles south of Cima Dome, locals recorded a two-year stretch — from October 1912 to November, 1914 — in which not a single drop of rain fell. This was notable primarily because someone was there to count the raindrops. No one is there now: Bagdad these days consists of a sign and a concrete pad. In the Lanfair Valley, 25 miles east of Cima Dome, the same years that saw not a single raindrop in Bagdad were rainy enough that new settlers were persuaded to clear a few acres of Joshua trees, commence to growing wheat. It worked for a few years, and then the rain went elsewhere. Some of those pioneering families’ descendants still live in Lanfair Valley. They buy their wheat in five-pound bags of flour, or baked into bread.

The Joshua trees their ancestors razed have not, for the most part, grown back.

Averages are irrelevant in the long term. It’s the extremes that are important. It’s the hundred-year frosts that define how far north trees will grow, the thousand-year floods that carve the mountains, the catastrophic droughts that rid a species’ gene pool of all but the droughtiest traits.

Any living thing native to the Mojave, therefore, must possess a strategy or two to survive worse-than-usual dry. This even more true for plants than it is for animals. Animals, after all, can wander around looking for water. Plants are pretty much stuck wherever they happen to sprout. Their drought survival techniques are various and clever. Cholla and barrel cactus send out a web of hair-thin roots to suck up all the moisture they can get. They then store it — for years if they have to — in fleshy, succulent stems. Some trees can send roots deep enough to reach water tables well below the surface. Mesquite roots have been found eighty feet down. Creosote bush holds on to whatever water it can find by sealing its leaves in a thick resin that retards evaporation, and poisons the soil around itself to reduce competition from other plants. And many plants contend with drought by just plain avoiding it. Hundreds of Mojave wildflower species germinate, grow, flower and set seed all in the course of a single wet season. Their seeds then lie dormant in the soil until the next favorable season, a dozen years hence, or twenty. Send a wetter than usual winter their way, and they will mantle the desert in color in March and April.

Where drought endurance is concerned, Joshua trees are cafeteria generalists. They store some water in their succulent tissue, like the cacti. Their roots, though not as fine-gauged as cactus roots or as aggressive as the mesquite’s, do spread out over quite a distance to collect rainwater. (Their leaves help, collecting any rain that falls on them and funneling it down the stem toward the trunk.) And in a sense, they avoid the worst of the desert’s drought by growing where water is more available: at elevations higher than 2,000 feet above sea level where rain is more likely to hit the ground, on alluvial slopes where seasonal runoff flows beneath the surface, on broad plateaus like Cima Dome where the shallow bedrock holds back winter rain so that the trees might drink.

Of course to call the fact that Joshua trees grow only where there’s enough water to support them a “drought avoidance strategy” is, in effect, to credit the trees with a greater ability to strategize than is usual for plants, which even I am not quite ready to do. At least not while other people are listening. The trees survive and reproduce where the drought is not too harsh for them. When conditions change, the tree’s fortunes change as well.

This is really nothing new. Plants have contended with drought, in one way or another, since the first land plants crawled up out of the trilobite-infested ocean to root on terra firma, 425 million years ago or so. Before that, the entire land surface of the earth was a desert. We animals faced the same dilemma when we climbed out of the ooze at about the same time. Land plant and land animal alike, we’re all just complicated bags of water wandering around. Even in the rankest, most humid places, our task is basically to find the water we need, take it in somehow, then keep it all from running right back out before we’re done with it.

It’s just that the stakes are higher in the desert. Water is in short supply. It becomes what the biologists call a “limiting factor” in life’s exuberance. Or what the economists call “currency.” Life orients itself around the getting of it, the saving of it, the opportunistic purloining of it. Those that fail, through misjudgment or bad luck or because the whole system is stacked against them, go bankrupt.

Here is one of the ways in which water limits the growth of Joshua trees: only in a wetter than average year will any Joshua tree seedling survive very long after germination.

I have been watching Joshua trees of varying ages for much of my life. I have sprouted their seeds on windowsills and warm, bright shelves. And yet I might still have trouble identifying those new, spear-like leaves beneath the cholla, if I encountered them on a typical desert hike, as the first leaves of a seedling Joshua tree. They look like grass. They are incongruously lush, supple and smooth.

They are also defenseless. Not yet equipped with the stout terminal spines, razor-sharp margins and bitter contents that characterize the leaves of an older Joshua tree, they are vulnerable to any passing animal that eats plants for a living. They are vulnerable to even the normal level of drought, not having had time to send roots more than a few inches out into the surrounding soil. But the bit of shade the cholla casts, the protection it provides from jackrabbits’ questing mouths, the sparse cast-off organic matter of cholla buds and the nutrient-rich offerings of perching birds will each of them help the Joshua tree seedling struggle along. The cholla lowers the likelihood of the seedling’s demise from certain, to merely almost certain.

This interaction between cholla and seedling Joshua is referred to, in ecologists’ parlance, as a “nurse plant” relationship. The metaphor is inexact. Actual nurses rarely find themselves being done in by their pediatric patients. If this baby Joshua tree lives, it may eventually crowd out the cholla, ravenously drain the water from the soil around it, block out the sunlight with its swelling canopy. The desert is full of trees with the husks of dead nurse plants at their bases. Of course, this Joshua tree seedling won’t pose that kind of threat to its nurse for many years. Before it can, it has to make it through its first summer.

•••

It does rain in summer in the Mojave, but summer rains are of a wholly different character from those of winter. Winter rains push themselves into the desert from outside. Summer rains wait to be invited. The desert draws them into itself. Intense summer heat in the desert makes the air rise, drawing cooler air in from surrounding lands to replace it — a siphon. Two hundred fifty miles south of Cima Dome is the Sea of Cortez. The siphon draws moist air from the sea up the valley of the Colorado River.

Even at dawn — even before the sun has done more than turn the eastern sky pink — the summer heat is palpable. When the sun finally appears, the heat quickly becomes oppressive. At lower elevations it can be nearly psychoactive. I walked with a friend one summer afternoon out onto the floor of Death Valley, the soles of our boots 252 feet below sea level, the air temperature some 120 degrees. The heat grew legs and walked with us, mocked our presumptuousness at venturing out into that dazzling wasteland of alkaline crystals. Every once in a while a breeze would play around us, but a hundred-twenty-degree breeze is no help at all. I had drenched my clothes with drinking water as we set out. They had dried by the time we were twenty paces from the truck. We walked a quarter mile out onto the playa and then a much longer quarter mile back, just enough distance to reach my truck before the walk depleted our fun reserves. Our drinking water was gone before we turned around. Had we needed to cross the entire valley on foot I might have missed out on all the subsequent excruciating joy my life has brought me.

At Joshua tree elevations, the heat is more survivable. At a mere 112 degrees, if I carry a gallon or two of water, pace myself, and find whatever shady spot the rattlesnakes will cede to me, I actually enjoy long summer afternoon hikes through the Joshua trees. After a few days I acclimate. I begin to relish the delicious coolness of sunset, when the air temperature drops back down into the double digits.

The next day is hotter. The day after, hotter still. The air fills with haze. Out on the valley floors thermal winds begin to scrape the soil from the face of the earth, fling it into the sky in the blond tempests known locally as dust devils. It is as though the desperate desert would do anything to shield itself from the relentless sun. The only animals foolish enough to venture out in the afternoon are ravens and nature writers. Everyone else waits for dusk.

And then the haze shifts in color from tan to gray. An odd scent fills the air, familiar but hard to place. It is only when the first clouds assemble themselves, seemingly out of nowhere, that I recognize the scent.

Rain.

The summer drought is unwilling to surrender. The clouds’ undersides seem to dissolve suddenly into gray sheets of rain, wispy tendrils aching for the ground far below. The parched desert air, greedy, sucks the water from the rain before it reaches the ground. I have spent hours driving beneath such clouds and never needed to reach for the wiper arm. This is virga, the evanescent desert rain that falls but never lands. I see the rain, its scent plays around my nostrils with the dust and creosote resin, and yet my lips still crack and peel.

At length the air has drunk enough, and the mounting heat intensifies the wandering storms. Rain reaches the ground.

Winter rains can be relentless, washing out bridges with their sheer persistence, but the desert’s summer monsoons are treacherous. They are intense, and intensely local. Desert hikers drown distressingly often in flash floods generated by storms they never saw. The sky may be an uninterrupted field of turquoise, the only hint of danger a far-off roll of thunder. The torrent in the wash catches them unaware. A few days after such a storm you can follow its path across the desert by tracking the swath of renewed growth, as though a huge paintbrush had been dipped in green gouache and then traced across the landscape.

From the porch of my little house outside the Mojave National Preserve, I watch clouds build over Cima Dome. The sky to the south turns dark. Muted lightning flashes inside the clouds. I grab the keys to my Jeep. The washes are full and flowing. An inch or two of silty water tops the pavement where they cross Morning Star Mine Road. The valley is a cauldron, wet and filled with steam.

I round the south end of the Ivanpah Range and ascend Cima Dome. The storm has almost passed, carrying its rain toward the Ivanpah Valley to the east. My campsite is a puddle. Cactus wrens drink from the ground, fly up to the tops of the rocks to scold me.

The little Joshua tree in the wash has survived the summer, so far. A trace of water runs past it. Its supple leaves are bent with the weight of raindrops.

In two hours most of the wet has sunk in, or evaporated. The desert is always thirsty. No storm is ever enough to slake the desert. Still, the mature Joshuas look greener already, watered well for now, the dust washed off their leaves. Sage sparrows fluff their breasts and shake, and chatter. The storm has been a welcome reprieve.

Another leaf emerges from the Joshua seedling’s heart.

Over the next few months the little tree will barely gain in stature. New leaves will sprout from time to time. The older ones will fade, die back, form a gray wreath around their younger siblings. Roots will branch, their new tendrils searching out moisture and nutrients among the desiccated sand and gravel. By this time next year, if the tree still lives, it will bear its first mature leaves. They will be stout and sharp, fiendish spines and razor margins, unpalatable to all but the most determined eaters of leaves. The tree will have passed a threshold most of its kind never even reach.

It’s not there yet. Each storm like this strengthens the seedling’s grasp on the Earth, lets it root itself more firmly into the soil of Cima Dome. Still, those roots remain mere threads by which the little Joshua hangs on to life. They are not yet sufficient to quench the seedling’s thirst. Along with the rest of the desert, the little Joshua tree awaits the next rain.