Fact Sheet #3: Plants of the Dune Field

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Fact Sheet #3: Plants of the Dune Field

The desert is not an easy place for plants to live. There is very little water in the Tularosa basin. Precipitation, or the amount of rain and snow that falls, averages only about 10 inches each year. Most of the rain falls in July, August and September. The rest of the year is very dry. Temperatures during the summer can soar to 110 degrees during the day, then drop to 50 degrees at night.

A lack of water is not the only thing that makes living in the dunes difficult. Windstorms come up from the southwest in February and March. They can last for several days, and wind speed can reach 45 miles per hour. During these windstorms, the plants are blasted by the blowing sand. Desert soils also have very few nutrients, like nitrogen, potassium, and phosphorous, that plants need to stay healthy.

You might think that desert plants are always struggling, always fighting to survive in these harsh conditions. But they do quite well here.

Desert plants have adapted to their surroundings. They have changed in ways that help them to conserve water, and grow in the very poor desert soils. The fourwing saltbush grows very well in the salty soil, and sends its roots deep into the ground to get to water. This is an easy plant to spot because its seeds have four, papery wings. The pickleweed also likes salty soil. This plant can grow in salty soils that no other plant can survive in.

Plants lose a great deal of water through their leaves by evaporation. What do you notice about the leaves of desert plants? They are usually very small. Big leaves would allow too much water to escape. But small leaves helps the plant conserve water. You may also notice that the color of the leaves are different. They are rarely bright green. Instead, most are a dull gray. If you look closely, you will see why. The leaves of some plants are covered with tiny hairs. Leaf hairs help to shade the plant from the sun, and protect it from being dried out by the wind. Other plants have a thick, waxy covering on their leaves. This is called a cuticle, and it also helps keep the water in the leaves from evaporating.

A few plants look like they don't have any leaves. The Mormon Tea plant looks as if all its leaves have fallen off, and all that's left are bare twigs. The leaves of the Mormon Tea have become so small that you can hardly see them. They don't even work like the leaves on other plants. Most plants make food in their leaves, but the Mormon Tea makes food in its green stems.

Some plants, like those in the cactus family, don't have any leaves at all. Their leaves have changed into sharp spines that protect them from being eaten by animals, and also help to shade the plant. The members of the cactus family come in many different shapes and sizes. The cholla is very common at White Sands. It is very tall, with long branching arms that break off easily and usually fall all around the base of the plant. The prickly pear has wide, flat pads that look like paddles. Some native people like to eat the fruit of the prickly pear, called a tuna. The claret cup hedgehog has short, fat stems that look like little barrels.

There are many plants that have adapted to living in the desert. In the whole Tularosa Basin there are 240 different kinds of vascular (stemmed) plants. As you get closer to the dune field, it becomes more and more difficult to survive, so fewer plants are found. Only 60 different kinds can live within the dune field. Most of these live in the interdunal flats between the dunes.

The big problem plants have in the dune field is being buried by moving sand dunes. Plants can't walk away from a dune that is starting to bury them. Most of the time the plants simply die because they can no longer get the oxygen they need once the sand has covered them. Living on top of the dunes requires very special adaptations. Only a few kinds of plants have managed to adapt in ways that will allow them to survive the moving sand.

One way a plant can survive is to grow faster than the dune is moving. The soaptree yucca uses this strategy. When it begins to get buried, the stem of the yucca starts to grow very rapidly and pushes the green leafy part above the surface of the sand. The stem can grow as much as 12" a year, and may get to be 30' tall. When you see a yucca plant on top of a sand dune, you can be sure that beneath it is a long stem that stretches all the way down through the sand.

Another way plants can survive in the moving sand is to try to hold on to a part of the dune. Plants like the Skunkbush Sumac can also outgrow a dune, with dozens of stems growing rapidly to keep its leaves in the sun. When the dune moves on, the skunkbush holds on to the gypsum and form a hard mound for the plant to grow on after the sand dune has moved away. We call these mounds “pedestals”. The Rio Grande Cottonwood, the only tree that survives in the dune field, also builds large pedestals by sending out roots from its buried trunk. The Rosemary Mint holds on to the sand with tiny, fast growing roots. If you look at the sides of these plant pedestals, you can see the exposed roots.

By growing faster than the dune can move, and holding on to the sand by building hard pedestals, a few plants are able to live very well on the sand dunes. But most plants growing in the dune field are found in the interdunal flats and around the edges of the dune field where the dunes are moving very slowly. In the heart of the dune field, it is a different story. Here the sand dunes are so big, and move so fast, that nothing can grow fast enough to escape.

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