Saturday, July 14, 2007

BBNP Photo Report ~ Scrub Desert Part Two

Most of the scrub desert in Big bend looks something like this:

If you are a desert plant, you have several goals evolutionarily, it seems: keep from overheating, keep your water, keep from being eaten. Thus plants have many options. To prevent water loss, many plants resort to physiology (C4 or CAM). To prevent herbivory, plants can invest in lots of spines and thorns, or have many secondary compounds. To prevent photorespiration and overheating, plants can put out small leaves that are either very waxy or very hairy. There are trade-offs, but in the desert we see winners. Sometimes we see combinations of many traits. Below is a lupine of some kind. The 'hairs', or trichomes technically, make the small leaves the prettiest color of blue.

The Resurrection Plant (Selaginella lepidophylla) is a desert adapted plant that fits somewhere between mosses and ferns evolutionarally. Most of the time, it looks like a completely dead plant. After rains, it reallocates resources and 'comes back to life'.

Often cacti flowers are very showy. Here the Chain Cholla (Opuntia imbricata) shows how such a wicked looking plant can also have great flowers. I've always really liked Chollas.

My first Big Bend trip was in many ways a sensory overload. By day three I had stopped trying to memorize the names of things. The leaves of this flower remind me of Broom Snakeweed, but I do not know the name of this plant.

Or this one.

Or this Orchid-like plant.

Near a place called Croton Springs we visited these petroglyphs. The place seemed very old. The first known group to live in the Big Bend were the Chisos Indians. These mild mannered agrarians were found then exploited by Cabeza de Vaca and the Spanish. The Mescalero Apaches were next in the region, followed by the Comanches. Who knows which group is responsible for this cinnabar artwork, yet here it is. Personally, I think this is Comanche in origin, as they were the most likely to revere bison, but who knows. There have never been bison in the Big Bend.

This place is almost religious. The sky was overcast and forlorn when we visited. The air cool and still. The particular rock formation where this 'canvas' is found, is at the very bottom of an arroyo cut through alluvial outwash. Several rocks were sculpted by eddies from years of flash flooding.

Our rudimentary geology wouldn't allow us more of an interpretation. I wondered at what a 20 foot high flash flood might be like.

There is food here too if one looks. Here is the fruit of a strawberry cactus (Echinocactus enneacanthus) which tastes like watermelon with the consistency of kiwi.

I don't know the name of this plant. I think the color of orange is really great though.

The most dominant dicot shrub in the scrub desert is Creasote (Larrea tridentata). This plant has small leaves high in terpenoid compounds. The terpines give the plant it's name, though it is not the same compound as the oil derivitive. The leaves are fairly pungant, and give the desert a distinctive smell after the rain. They have an amazingly delecate flower.

Sometimes one sees a Creasote 'seed' move. Creasote mites are remarkably similar to Creasote seed pods. But, an insect.

I don't know the name of this shrub. It seems very 'Orchid'-like as well, though I suspect it is a dicot.

At the higher elevation desert, Purple Sage (Leucophyllum frutescens) comes into the assembly of species. I suppose Zane Grey knew of this plant.

This Euphorb Candelilla (Euphorbia antisyphyllitica) is used by Mexicans to make wax. They boil down this plant, separate the waxes, condense it and then smuggle the wax into the US as recently as the 1980s. The specific epitath suggests other usefull properties in addition to the wax. The flowers almost look like they are just tacked on.

An old Mexican vaquero described how to get to the Big Bend: "You go south from Fort Davis until you get to the place where the rainbows wait for rain, and the big river is kept in a stone box. And the water flows uphill. And the mountains float in the air, except at night, when they run off to play with other mountains." This seems to make sense after visiting. I think for me the 'rainbows waiting for rain' represent the plants and thier flowers.