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Vision Quest 2016: Hidden Diversity

Tuesday, May 31st, 2016: Mojave Desert, Trips, Vision Quest 2016.

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After leaving the desert, I visited family in the Midwest and hiked in a lush temperate forest, an environment which is paradoxically much less diverse. In the desert, the lack of an arboreal canopy allows life-giving sunlight to reach the ground almost everywhere. The patchy nature of vegetative cover has resulted in level upon level of diverse flora, from lichen and soil crusts at ground level, to tiny forbs, larger forbs, sub-shrubs, shrubs, various forms of cactus, agaves and yuccas, riparian trees, and the conifers and hardwoods of upland slopes. More leafy annuals and perennials, as well as mosses and ferns, are found in the shade of boulders and cliffs.

While armchair adventurers dream of exploring outer space, the desert is a true frontier nearer at hand. Here, mysteries abound and alien life remains to be discovered. Scientists have identified only a fraction of plant species in the desert, and are discovering new ones constantly. Much of the desert’s diversity is hidden at ground level, or far from the highway. It takes an effort to find it, but the rewards never fail.

Worlds Apart

The day I arrived on my land, I eagerly hiked up the wash looking for water. The first thing I noticed was that the desert lavender was blooming, and the bees were swarming it. Desert lavender, Hyptis emoryi, is sparse in our canyon system, which is dominated by desert willow, Chilopsis linearis.

The following week, I hiked into the next drainage to the north, only two miles away, but separated by a high ridge. There, I found desert lavender to be dominant, and desert willow completely absent.

During my decades of exploring mountain ranges in distant corners of the desert, with their dramatically different forms, colors, and geologies – from sedimentary to metamorphic, from plutonic to volcanic, and mixtures of the above – I’d noticed subtle differences in the vegetative cover and isolated differences in the dominant plant species. But on this trip, prompted to revisit adjacent canyon systems in my home range, I discovered that even in a single mountain range, different drainage basins can have dramatically different botanical signatures.

The canyon system spanned by our property has a floral mix that I’ve known for so long that I take it for granted and barely notice it on a conscious level. From the alluvial fan at 2,500′ on the edge of the mountains to the watershed on the ridgetops at 5,000′, the dry washes and gullies are dominated, in succession, by desert willow and catclaw acacia, then catclaw with baccaris or seep willow, then coyote willow, and finally juniper, pinyon pine, and shrubby hardwoods. There are three small clumps of mesquite scattered far apart, noticeable but barely hanging on.

The beautiful canyon that I discovered on the second day of the survey was dominated by mesquite – perhaps 30 times as much as I’d found elsewhere – followed by long-established tamarisk, the destructive exotic.

These drainages may be separated by as little as two miles, but the intervening ridges create a barrier from hundreds to thousands of feet high. Still, it surprises me that certain plants haven’t been able to colonize adjacent drainages, using humans, birds or rodents as seed carriers, during thousands of years of relatively stable climate.

My last stop in the desert was one of our biggest ephemeral watercourses, a corridor of green draining a huge alluvial basin, shaded by a canopy of tall, old-growth palo verde, a tree which is sparse and generally of modest size elsewhere in the Mojave. Unlike many less arid habitats, the desert is surprisingly diverse.

My Mountains: Watercourses

Riparian diversity has been reduced in many parts of the Southwest by the invasion of tamarisk, a shrub from the Middle East which was accidentally introduced in the 19th century when its non-invasive cousin was planted in windbreaks. Once tamarisk blooms, it’s impossible to keep its zillions of tiny seeds from blowing across the landscape or washing downstream in flash floods. As a result, it’s in virtually every canyon in the desert, to greater or lesser extents.

Invasive plants generally only colonize soils disturbed by non-native intervention, by cattle or humans and their machinery, but riparian plants can take root in sand disturbed by natural flash floods. Once established, tamarisk emits salts that poison the soil and prevent native plants from thriving. My friends and I have worked hard, but in vain, to eliminate tamarisk from our land, and government agencies as well as volunteer groups have been attacking it for decades. Invasive species, and their damage, are here to stay.

But our native riparian flora hangs on in many places, and it’s always rewarding to come upon it.

My Mountains: Bajada

The bajada, a rolling shrubby upland at the foot of mountain slopes, is the hotbed of floral diversity in the desert. Toward the end of my trip, as the sky cleared after a morning thunderstorm, I ate some magic mushrooms that a friend had left with me years earlier, and spent the afternoon hiking the bajada, marveling at the blooming cactus and shrubs, as the sun went down and the multicolored plants seemed to glow from within as they were backlit from the west.

My Mountains: Upland Slopes

Slopes above 4,000′ host islands of conifers and hardwoods. I headed for this zone on my first big hike, and found both junipers and pinyon pine suffering from a mysterious blight. Fortunately it seemed to be confined to our drainage and didn’t appear elsewhere in the range.

Joshua Tree Woodland

After my arrival at the remote ecological field station, I was invited to join two botanists on an all-day field trip, looking for rare plants in the high desert. Jim, the leading plant expert in this region and one of my heroes, has worked tirelessly to catalog endangered species and fight solar and other developments that threaten desert habitat. He was taking Fred, a botanical illustrator, on a search for rare plants that will be featured in a book they’re working on. Jim brought us up to date on the dominant society’s greed and corruption as we drove from site to beautiful site.

People who follow the media may get the mistaken impression that our society is expanding its protection of desert habitat via a new series of national monuments, but in the fine print, these contain provisions that may actually accelerate mining and other developments.

The upland basins and gentle slopes of the Joshua tree forest that we visited first host a rainbow of blooming shrubs in springtime. They also tend to host more native bunchgrasses than other habitats, sometimes forming broad grasslands with abundant, nutritious forage for wildlife.

Limestone Slopes

From the Joshua tree grassland, we drove up onto an isolated ridge of limestone. These limestone mountains and outcrops are scattered among the dominant volcanic and granitic ranges of the desert, providing a substrate for some unique endemic plants.

Red Rock Canyon

Our final botanizing site featured a contact between granite and sedimentary rock, a literal rock garden for cactus and rare species, and an interesting canyon through gabbro, a coarse-grained plutonic rock with big embedded crystals.

Creosote Flats

The grad students I met at the field station were pioneers in the study of ecological facilitation, the beneficial cooperation of very different plants and animals in their habitats. The desert is a frontier of this new field, showing how little science really knows about the earth, as research continues to uncover more questions than answers.

The graceful, drought-tolerant creosote bush, a “medicine chest” for desert Indians, achieves nearly pure stands in sandy low-elevation basins. These basins appear barren to the inexperienced eye, but may provide critical habitat for desert tortoise, pollinators, and many other species. These habitats, with their austere beauty, are the first to be sacrificed for giant solar energy projects.

Granite Peaks

After leaving the ecological preserve, I camped out at higher elevation in a lush basin surrounded by granite peaks.

Overgrazed Valley

Next, I drove a couple of mountain ranges north and hiked into a remote valley hoping to find a beautiful canyon I’d discovered long ago. Instead, I found half-wild cattle and a trampled and overgrazed landscape. It was a mistake to introduce cattle to this landscape in the first place, and it should be a crime to run them here now.

Badlands Oasis

I joined conservation biologists on a field trip to the Amargosa River to study endangered toads, and we found a wetland and riparian corridor recently recovering from the removal of invasive tamarisk.

Tunnel of Shade

Before leaving the desert, I stopped at a huge dry watercourse with a forest canopy that had always intrigued me, far to the east of my mountains. This 20-mile-long wash channels the occasional powerful flash flood, but is dry at other times, providing a rare tunnel of shade from high on the alluvial fans to the distant Colorado River.

Sonoran Outliers

At the eastern edge of the California desert, iconic Sonoran Desert plants appear, in a narrow band along the western shore of the Colorado River: ocotillo here, and saguaro cactus farther south.

  1. JOAN GREEN says:

    Amazing, isn’t it! this is desert but it is alive with wonderful living plants.

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