Deserts cover about one fifth of the Earths surface. Deserts are very harsh and dry. Deserts usually receive only twenty five centimeters of rain per year. The maximum temperature in the desert is about fifty degrees Celsius.
Some times when it rains in the desert the rain is evaporated before it even hits the ground. Animals and plants have found ways to adapt to the Earths driest and hottest deserts.
Plants Adaptation to the Desert Biome:
Different plants have different ways to adapt to the desert. They have their own way to preserve and get water. Some plants have developed tap roots. These tap roots can extend to thirty meters below the surface to draw water out of the water table. Other plants have shallow roots to catch water as soon as it lands. Desert sand is well drained and water doesn't sit around on top. This means water can soak into the ground very fast.
Some plants such as the spines or fur trees reduce the heat by facing leaves directly up or down to minimize surface area hit by the sun so less water is evaporated.
Other plants like the Joshua tree have small knife like leaves that have a very small surface area. The small surface area means that less water is evaporated. This tree also has a waxy resin that prevents much water from evaporating.
Another plant called the living stones exposes only a few of its leaves. Most of them are underground along with the main body. This is done so it doesn't loose all its precious water to the sun. The tree is also kept cooler.
The Mosquite tree has adapted to the desert by having roots that can extend 30m into the ground. This is so it can tap into the underground water supply.
Living Stones
Joshua Tree
In the desert many plants space out from each other because the water is scarce. If the plants were close together like the bush around Northam many wouldn't survive. The plants would be competing for water and only the hardiest would survive. Another adaptation is that some kinds of plants have chemicals or poisons in its roots to keep other plants from growing nearby.
A tree called the Creosote has adapted a taste and smell that wild life find unpleasant. It has leaves that closes in the day and stays close to the stem to reduce water evaporation, and that open at night to absorb moisture. This plant has also adapted duel root systems that tap deep in the underground water and radial roots that collect the surface water.
Some plants only open their stomata at night time for gas exchange this is because evaporation rates are lower than day time and there is less chance of water been lost.
Some plants that do this are the cactus and the agaves
Creosote Bush
The grasses in the desert have adapted strong roots to hold them in place so when the desert sand is moved in strong winds the plants are able to stay in place. Some plants can anchor a whole sand dune in place.
Desert Grass
Other plants also direct the shiny side of their leaves to the sun to reflect the suns rays so less water is evaporated.
Some plants also slow down their growth rate for the drier half of the year to conserve water.
Many large cacti like the barrel or organ pipe cacti can store huge amounts of water in their stems and pulpy interior. The saguaro cacti has adapted to grow in harsh rocky and gravel soils because of its roots only 2.5cm under the ground so it gets every chance to soak up the rain or dew before it evaporates. The saguaro also has a spongy inside layer so it can transport and hold water. It also has a stretchy skin that is able to expandable so it can hold more water if it is available.
The saguaro is a very slow growing plant it can take 80 years for it to reach six meters in height. By doing this it needs less energy, food, and water to survive. This makes it a very hardy plant in the desert biome. Cacti have adapted spines on them to shelter them for the sun, to keep animals away, and to collect dew and moisture. The cacti also have waxy skin to seal in the moisture and to prevent water loss through evaporation.
Barrel Cacti
Plants like the Acacia and the ocotillo have adapted to the desert climate to loose their leaves during long periods of dryness. The plants also drop seeds and then enter into dormancy. This works well because less water is lost through evaporation during the hotter drier months. During dormancy water is retained by the trees waxy skin which traps water inside.
