the Desert Part 1

This is my school report for plants. I was assigned to talk about the plants in the desert. Take a look and tell me how you guys think about it. This report will be broken up into a few parts so that you guys can comment on certain sections and read it easier. It will not be just one giant report.

There are numerous biomes in the biosphere that we live in that each have features and environments that make them unique in its own way. However, the one that interests me the most is the desert. Deserts are very extreme environments in which plants and animals must be able to adapt in order to survive. The variety of animals and plants that live in desert attribute to the evolutionary nature of organisms. The adaptations in these extreme environments are what make the desert so intriguing to examine. Also, the desert biome is unique in that there are many different types of deserts, each having differing in climate settings and accordingly plant and animal life. Deserts encompass approximately 20% of earth’s land surface. They are mostly located between 20o and 35o latitude, North and South of the equator. What makes deserts so special are their diversity that can be contributed to varying degrees of temperature, precipitation, and location. There are four major categories that can be attributed when describing deserts: hot and dry, semiarid, costal, and cold. Each type of desert carries distinct traits and qualities.

Hot and dry deserts exhibit very hot summers and are warm year-round. Average annual temperature ranges from 20-25o C. There is very little humidity in these types of deserts, often averaging less than 1.5 cm of rainfall. The rainfall almost exclusively falls during the winter and rarely in any other seasons. These hot and dry deserts receive almost twice the amount of sunlight radiation in the day than most other biomes, which causes radical temperature changes between day and night. In the summer, during the day temperatures may reach as high as 48o C, while at night temperatures may drop as low as -18o C. Soils of hot and dry deserts are course-textured and rocky with good drainage.

Semi-arid deserts have moderate long, dry summers. The winter brings occasional low amounts of rainfall. Summer temperatures usually range between 21-27o C, rarely exceeding 28 o C. At nights the temperature usually drops to 10o C, not as extreme a change as hot and dry deserts. Average rainfall for these types of deserts usually range between 2-4 cm annually. The semi-arid soil has a mixture of fine particles and rocky fragment, which allows for good water drainage, same as the hot and dry soil.
Coastal deserts are situated in locations of cooler temperatures than the previous two. They have cool winters that usually max out at 5o C are followed by warm summers with temperatures ranging between 13o C to 23o C. Average rainfall in these deserts are found to be between 8-13 cm. The soil is fine-textured with a moderate salt content, and is fairly porous which allows for good water drainage.
Last the cold desert is characterized by long, frigid winters with snowfall and high rainfall. There is also rainfall, though not as much, in the summers of cold deserts. The average temperature in the winter ranges between -2 to 4o C, while the summers range between 21-26o C. Average precipitation, which includes both snowfall and rainfall, is between 15-26 cm. Rainfall is most prevalent in the springtime usually in April and May. The soil is heavy and salty, due to the rainfall and is relatively porous with good drainage.

There are many plants that inhabit the different types of deserts. The plant that I will go into detail is the perennial Sarcobatus vermiculatus, more commonly known as greasewood. The Latin name “Sarco” is Greek for fleshy, which describes the fleshy leaves that the plant has. “batus” is Greek for spiny, which describes the spines that cover shrub. The Sarcobatus vermiculatus plants are three to eight feet tall shrubs that can be found in plant communities from Mexico to Canada, but are most prevalent in cold deserts north of the 37o latitude. Sarcobatus vermiculatus are able to withstand temperatures as high as 43o C to as low as -34o C, proving their ability to adapt even in the most extreme temperatures. Because these shrubs are most prevalent in cold deserts, they are able to survive with scarce water supply. These shrubs are halophytic meaning they can survive and complete their life-cycle in areas of high salinity. Because of their adaptations, they are able to survive in soils of high salinity or alkalinity, which are highly represented in cold deserts. They are also able to establish themselves in nonsaline soils; however, Sarcobatus vermiculatus will not establish themselves in nonsaline soils in the presence of nonhalophtyic competitors because the competitors would heavily decrease their chances of survival.

Like all plant-life, the Sarcobatus vermiculatus experience many seasonal changes. The leaves of the S. vermiculatus are winter-deciduous, meaning they tend to fall off during the winter seasons, and therefore, are usually displayed from late spring to early autumn. They usually flower between late May and early July right before the intense summer heat comes. Male flowers release pollen in early June, while female flowers do not become evident until later in the month. During the summer, between mid-June to mid-September, soil moisture is usually at its lowest and temperatures are usually at its highest in relation to the year. Therefore, it is between this segment of time when S. vermiculatus are least prevalent. Seeds mature between September and November and dispersal occurs in early winter. The S. vermiculatus drops its leaves in early winter.
One of the more prominent adaptations that allows the S. vermiculatus to resist alkaline surroundings is its succulent leaves. Succulent leaves are large fleshy leaves that are have specialized water-storing tissues, which allows the leaves to store more water to offset the sodium intake in these shrubs. The leaves are mostly composed of these water-storage tissues and covered by photosynthetic tissue, enabling the leaves to undergo photosynthesis as well as store water. (S. vermiculatus undergo C3 photosynthesis) S. vermiculatus accumulates sodium in its leaves, and creates a salt-enriched site under its canopy from salts leaching out of the succulent leaves. These sodium accumulations in the succulent leaves increase the soil to plant water potential gradient, which increases the plant’s ability to acquire water and other nutrient ions from the soil. These accumulations of sodium are what facilitate the plant’s tolerance to saline soil. Also in alkaline soils, Sarcobatus vermiculatus have smaller and thicker leaves. The smaller the leaves the less surface area from which water can escape from, and the thicker the leaves the higher volume of water the leaves can hold. S. vermiculatus like most other halophytes increase the amount of proline and glycinebetaine when salt concentration increases. Proline and glycinebetaine are compatible solutes to the salt, and as a result, they are able to restore and maintain the osmotic balance of living cells when salt concentration radically changes.

Since Sarcobatus vermiculatus tend to live in deserts, the soil is relatively dry when compared to soil in other biomes. Therefore S. vermiculatus must readily learn to adapt to droughts. In regions of scare water supply, S. vermiculatus are usually found in areas with large distribution of groundwater. These shrubs have been found to have a unique root system that helps them obtain the groundwater. They better obtain water by having a dense, relatively shallow root system with a deep taproot. The shallow root system is common in most deserts plants because the roots are able to more efficiently collect water that drains from the surface of the terrain. The deep taproot extends to well below the soil surface to access the subterranean moist soil. This taproot is especially important in the summer when the upper soil layers are relatively dry. By tapping into the more water-filled soil below, the taproot is able to hydrolyze the plant and keep it green and succulent throughout the summer seasons. Sarcobatus vermiculatus have also been found to drop their leaves and reduce canopy size during a drought to retard water loss through the stomatal openings.

The seeds of Sarcobatus vermiculatus germinate in early spring, which insure that the seeds sprout and flowers mature before the intense heat of summer. The seeds are set to sprout according to soil temperature and moisture. Germination of Sarcobatus vermiculatus is temperature-dependant; the optimum germination for these shrubs is approximately 9-10o C. Sarcobatus vermiculatus are monoecious plants, meaning that they have both male and female flowers. The male flowers are developed in the fleshy, cylindrical spikes at the ends of the stems. Female flowers are developed singly in axils of the leaves. However, because both male and female flowers are located on the same plant, self-pollination may occur. Therefore to prevent self-pollination and increase the chances of cross-pollination with other plants, the male and female flowers mature at different times. The male flower generally matures first and then is followed by female maturation. Maturation is fully complete between August and September. S. vermiculatus seeds may be dispersed up to 700 meters away from the original shrub. This dispersal distance demonstrates how most desert plants are situated. Because of the scarcity of water, plants must be spaced further apart. By being spaced farther apart, the desert plants will not have to compete with each other for the already scarce water supply. Each Sarcobatus vermiculatus will produce around 20 seeds when undisturbed but up to 250 seeds when the plant is disturbed. This exponential increase in seed production will be relevant when discussing its adaptation to fires.

In some habitats, there are always possibilities for fires, especially in deserts. As such, many of the areas the Sarcobatus vermiculatus inhabit are subjected to the risk of fires. Sarcobatus vermiculatus are known to be viable in areas of frequent fires because of their quick re-sprouting. Most of the time, the Sarcobatus vermiculatus plant is not completely destroyed and therefore can re-sprout from its original stem base. However, if they are completely destroyed, Sarcobatus vermiculatus can disperse through wind and re-establish themselves quickly. As stated above, when a Sarcobatus vermiculatus plant is disturbed it can increase the number of seed production, which makes them so ready to repopulate in case of fire damage. The S. vermiculatus are able to re-sprout very quickly after being burned (around 2.5 ft in 3 years). The re-sprouting often leads to an increase in stem density to create a greater resistance to future fires. Also, S. vermiculatus can re-sprout after application of herbicide. In fact, it has been found that they increase plant size growth by increasing its vegetative growth periods following application of herbicide. Both these examples emphasize the S. vermiculatus plant’s ability to positively adapt to adverse conditions. The S. vermiculatus must be commended for its malleability in the face of distress.

The S. vermiculatus also needs to protect itself against wildlife predators. One of its defenses is the spines that are situated on the branches of the S. vermiculatus plant. Though not particularly sharp, they are able to keep away more sensitive creatures. A more significant defense is the salt concentration in the leaves of the plant. The leaves are known to contain high oxalate or sodium concentrations. When large amounts of oxalates are consumed, the animals may be poisoned, which can result in weakness, nausea, or even death. Therefore, the amount of salt and oxalate concentration in the leaves of the S. vermiculatus is important in keeping predators from repeated attempts of feeding.

This is my report on desert plants. I hope you guys learned a little something about desert plants haha. I had to do this project for a upper level biology elective at college. I want to know how you guys feel about this so that I could correct it. Thanks!