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This is actually a joint diary by yours truly and richholtzin, the geology genius who usually treats us to this fantastic series. I got in touch with him a few months back when I first planned a trip to Joshua Tree to see if he had already done a post on it. He said he hadn't... but I could after my trip! I've asked Rich to put up a tip jar after this post, so please please tip him for his contribution :)

Joshua Tree National Park is named for (duh) the Joshua Tree. Legend has it that Mormon settlers named it for the biblical figure because it looked like a person standing in the desert, beckoning them to continue west. It's actually not a tree at all, but a species of Yucca.


A Joshua Tree (Yucca brevifolia)

Despite the name, you won't find Joshua Trees in every part of the park. The park is cool because it spans several different ecosystems, including both the Mojave and Sonoran Deserts. My recent trip took me to several plant communities on the Mojave side - Juniper-Pinyon Woodland, Creosote Bush Scrub, and a Desert Fan Palm Oasis. So if you're ready to see more, buckle up and join me below the fold.

I was first introduced to Joshua Tree, believe it or not, by a Kossack. Years ago, Occams Hatchet invited me to his family campout there. And I don't know if it was me or Googlemaps who had the brain fart, but the drive took hours more than I'd expected and I got there after dark and wasn't packed appropriately to spend the night in the cold weather. I ate some s'mores, hung out, and went home. Lesson learned: Yes, it's the desert, but it gets COLD.

If You're Planning a Trip: After going back to J Tree better prepared this time, here's what I can tell you. There are several different entrances to the park, each near different campsites and attractions, along the north rim of the park. There are only two campsites within J Tree that take reservations, and both are accessed from the north - Indian Cove and Black Rock. You can also pop into J Tree for a quick hike at the 49 Palms entrance. The mile and a half trail takes you to a desert palm oasis. (There are other park entrances too, and I'd imagine you'd need to enter from the South if you're visiting the Sonoran Desert side of the park.)

Before picking your campsite, do a bit of comparing and contrasting the amenities at each one. Black Rock is one of just two sites in the park that has running water and lovely flush toilets and sinks for washing hands. Indian Cove has clean, non-stinky outhouses and no water. However, Black Rock is not where you want to go for rock-climbing, and Indian Cove's a fantastic rock-climbing spot. And, if you're not backpacking, it's pretty easy to pop out of the park in your car to pick up water or firewood in town during the day, so running out won't be a total catastrophe.

Furthermore, the campsites at Black Rock are packed close together, which causes some problems. My group wanted to be loud and rowdy til about 3am... the Boy Scout troop next to us wasn't so happy about that. Next time, I'd get a campsite at Indian Cove instead, where the huge rock formations force the campsites to be much further from another. Then my friends can be rowdy and obnoxious in peace.

Another recommendation? Check daytime AND NIGHTTIME average temperatures for the time of year you plan to visit. It gets hot in the day and cold at night. In early April, when I went, it was in the high 80s in the day, and in the 60s at night. And the 60s isn't too cold... unless you're sleeping on the ground in a tent. Then it's pretty cold. When I visited in October, I remember wearing mittens and a hat at night because it was even colder.

Given the fantastic biodiversity found within J Tree, I was extremely disappointed at the lack of resources available to help me plan a trip so I could see as many plant communities and plants as possible. A map of the park color-coded by ecosystem would be nice, and to the best of my knowledge, none exists. It seems like most folks who want to go are there for hiking, biking, horseback riding, camping, and - maybe most of all - rock climbing. (BTW, I think it's BYOH - Bring Your Own Horse.)

Speaking of rock climbing - here's another recommendation: Come prepared for first aid. Between rock climbing, sunburns, cacti and prickly plants, and whatever else, you can mess yourself up pretty well there. Fortunately, many of the plants in the park are medicinal (not that you're allowed to harvest them and use them) so if you know what you're doing, you can rely on them in an emergency. But really, it'd be better to just come prepared. A shade canopy and a big floppy hat are also good ideas, in terms of preventing sunburns in the first place.

Plant Communities
As noted above, I visited three major plant communities: Juniper Pinyon Woodland (at Black Rock), Creosote Bush Scrub (at Indian Cove and 49 Palms), and Desert Palm Oasis (at 49 Palms). I've already written up diaries on my own blog covering plant recognition and edible and medicinal uses for the plants found in these ecosystems (I highly recommend checking them out - here's Part 1 and Part 2). So for this diary, I think I'll give an overview of each community, and then go into a bit more depth on some of the amazing strategies these plants have for surviving and reproducing in such a harsh climate.

At Black Rock, you'll find Juniper-Pinyon Woodland. The site is at a high altitude (relatively speaking) at about 4000 feet. The main plants I saw around me at the campsite were Joshua Trees, Mojave Yucca, and Juniper. The area looked a lot like a scrubby desert environment, and it was not at all what I would have called "a woodland" at first glance. In fact, when we woke up the first morning, I visually scanned the nearby mountains to see if there was some woodland I could hike up to up there. I was bummed that the vegetation on the mountains looked the same as the vegetation in the camp, and resigned myself to the fact that I probably wouldn't see the juniper-pinyon woodland after all - at least not here. Then I went off to get some water and stumbled right into a juniper tree!!!


The spiky flowering plants are Mojave Yucca. See how this is not vegetation that reminds one of a pine forest?

My other cool finds at Black Rock included single leaf pinyon pine, ephedra, chia (Salvia columbariae), beavertail and cholla cacti, and many different colors of lichens. Animalwise, we just saw a bunch of California quail, squirrels, and an unidentified rodent that visited are campground at night. The quail and squirrels were getting fat off the dropped food of campers, and they put on quite a show as a family of quail got too close to a squirrel's "turf" and the squirrel noisily shooed them away.

At lower altitudes on the Mojave Desert side, you'll find Creosote Bush Scrub. This is a desert landscape that is almost entirely dominated by the Creosote Bush, Larrea tridentata.


A view of the desert at Indian Cove


Creosote flowers

Most of the plants in the desert were of the "Don't F*** With Me" variety. Either they had vicious spines and thorns, or they completely shed their leaves for much of the year - leaving herbivores with nothing to eat. Leaves also lose water when their pores (called stomata) open to take in CO2 for photosynthesis, so getting rid of your leaves is a way to avoid water loss. Some plants, often succulents like cacti, have perfected a clever way of doing photosynthesis (called CAM), allowing the stomata to only open up and take in CO2 at night when the sun isn't out, and then take care of the sunlight part of photosynthesis during the day.

The creosote is a bit unique among desert plants in that it has bright green leaves. The catch is that the leaves are covered with a sticky resin that makes the leaves nasty tasting or even poisonous to herbivores. The resin also protects the leaves from the sun.


Creosote bush leaves and buds - see the sticky resin?

Desert plants absolutely fascinate me in their adaptations to deal with this harsh environment. Some plant seeds can sit around for 50 to 100 years, waiting for the right conditions before germinating. Often, they require scarification, caused by lots and lots of rainfall, in order to germinate. That way, a wildflower seed in the desert can ensure that it will only begin to grow when conditions are just right.

Mesquite, another desert species (alas one that I did not see on this trip) has an incredible adaptation to the desert environment as well. Their roots can extend over 150 feet below the soil surface to search out water.

Creosote has another amazing adaptation to allow its reproduction in the desert. As you may imagine, it's the baby plants that have the hardest time. While creosote's furry-looking seedpods can grow into new trees, the tree more commonly reproduces by cloning itself. In fact, scientists have found a ring of creosote clones with a diameter of 45 feet that is 11,700 years old!!!

In addition to creosote, I saw plenty of cacti of course (cholla, barrel, beavertail, and hedgehog), cat claw acacia, brittlebush, apricot mallow, ephedra, and jojoba. There was also Mojave Yucca in this region, but it was much smaller than the Mojave Yucca found at Black Rock.

The third plant community I visited was a desert palm oasis. These occur in areas with year-round underground water. It's suspected that at least some of these were planted by California's indigenous people, since many are very far apart from one another and it would have been physically impossible for, say, a coyote to eat a palm fruit in one oasis, travel five days, and poop out the seed at another oasis to plant the trees there.


The palm oasis at 49 Palms. It looked almost like Emerald City rising up out of the desert.

Critters: So those are the plants. How about the critters? In addition to some ubiquitous SoCal residents like California quail, lizards, and squirrels, there are some special ones in Joshua Tree. For example, if you are very lucky, you might find a desert tortoise or a bighorn sheep. The park is actually home to 25 different kinds of snakes, including the Desert Rosy Boa, the California King Snake, the California Striped Racer, and more rattlesnakes than you can shake a stick at. But don't do that, really. It's not a good idea to provoke a rattlesnake.

I'll admit, I was hoping to see a desert sidewinder, but I didn't. If you're into critters, the J Tree website has info and checklists of the species present within the park. My favorite critter these days is the Kangaroo Rat, which is amazing because of its incredible adaptations to life without water.

Some, like kangaroo rats, have extreme adaptations enabling them to live without ever drinking water. They have super efficient kidneys that extract most of the water from their urine and return it to the blood. And much of the water that would be lost in breathing is recaptured in the nasal cavities by specialized organs. If that weren’t enough, kangaroo rats actually manufacture water metabolically from the digestion of dry seeds!
Rocks
I'm not a geology expert or even a geology novice, so I asked Rich Holtzin to contribute the geology section of this post because I know it's an important part of the park. Here's what he said:
The geologic landscape of Joshua Tree has everything to do with erosion over millions of years. So does percolating ground water. Actually, there's the secret of how this setting honed its fantastic shapes. What forces sculpted such engaging rocks? Here's a quick Geology 101 response that I hope makes sense to you.

Go back in time over 100 million years ago and envision what this landscape once looked like: super heated by the Earth's crust that was constantly changing (as it does today) a molten liquid oozed upward, cooling while still far beneath the surface. This process describes what geologists call "plutonic intrusions," in this case granitic rock called monzogranite. The unusual characteristic of this type of granite, however, is that it developed a template of rectangular joints, where one set that was more or less horizontal resulted from erosion of an overlying bed if rock, called gneiss (rhymes with "nice").

This description is just one phase of the process, for the other set of joins oriented vertically, thereby paralleling the contact point of the monzogranite with the encompassing rocks in this sector. There was also a third set, which is vertical, except its creation cuts the second set at higher angles.

As a combined result, this system of joints tends to fashion rectangular blocks.

Here's with the percolated ground water seeps through the monzogranite jointed fractures. The process eventually transformed some hard mineral grains along its pathway and turned the material into soft clay. At the same time, the process loosened and unloosened grains that were resistant to solution. In time, the rectangular formations slowly weathered (i.e., broken down) into spheres of hard rock entirely surrounded by soft clay containing loose mineral grains.

Everything just explained took its sweet time; millions of years, in fact. The climate at the time was much wetter compared to what we experience today. Indeed, you can even conduct your own experiment and see how the process works, say, on ordinary ice cubs. Simply turn on the spigot and watch as the corners of the cube are rounded.

Turning the clock of time's hands fast forward, climate has obviously changed. In this region, numerous flash floods wandered through and washed away the protective bed topography. Thus gargantuan-sized eroded boulders more or less settled one on top of the other. And this is precisely what we see given the impressive piles of rocks throughout the park.

Other geologic happenings are the telltale broken terrace walls one sees migrating through the boulders. These geologists call dikes. In this specific case, dikes are much younger than the surrounding monzogranite foundation of the park. Look closely and you see light-colored pegmatite, alpine and andesite intrusions formed as a mixture of quartz and potassium (minerals) that has been radically cooled in such tight spaces. Thus nature merely broke into the larger uniform blocks once exposed to the surface.

Here's something else to keep in mind while you wonder and wander through the park: water is potent agent of erosion. Even in typically arid environments it functions supreme. So is wind erosion (called "Aeolian" weathering). Nevertheless, the long-range effects of such erosion are minimal compared to water.

Now you know the secret of how this singular park and its topographical feature were created. Simply put: relentless erosion and weathering, as a process, in typical arid conditions denote the more astounding fabrication process that has sculptured the rocks throughout the park. Whereas before there were consistent higher rainfall and temperatures, the typical desiccated atmosphere of today's climatology tells an entirely different story given the before and after aspects of what happened here (and still continues). Today's appearance of these rugged mountains of literally twisted rock and exposed granitic monoliths are sound testimony to the tremendous heat, force and pressure that initially shaped and formed this unusual landscape in the Mohave Desert.
Think of the park as a huge mosaic of complexity, as well as stunning beauty. That's also what you tend to get where playas, alluvial fans, bajadas, pediments and arroyos embellish the geography of this California desert terrain.

Thanks Rich! Don't forget to tip him!

Originally posted to Jill Richardson on Wed Apr 10, 2013 at 07:03 PM PDT.

Also republished by DK GreenRoots, National Parks and Wildlife Refuges, and SciTech.

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