Hot Desert Biome PDF

Hot Desert Biome CLIMATE The climate of the hot desert biome is arid, experiencing high temperatures and little to no precipitation. Summer temperatures exceed 40 degrees during the day before dropping to 15 degrees at night. In winter daytime temperatures are 25 d...

Hot Desert Biome CLIMATE The climate of the hot desert biome is arid, experiencing high temperatures and little to no precipitation. Summer temperatures exceed 40 degrees during the day before dropping to 15 degrees at night. In winter daytime temperatures are 25 degrees but fall near 0 degrees at night. The direct angle of the sun means sun rays are concentrated over a small area leading to very high ground temperatures. As the soil has little to no vegetation cover, the ground absorbs all of this heat which radiates up from the ground leading to high atmospheric temperatures. Once the sun sets the lack of cloud cover allows heat to decrease rapidly, leading to the high diurnal range we see in these regions. Very little rainfall between 0 to 250 mm per year. Rainfall is not evenly spread and occurs in short torrential downpours that are quickly evaporated by the heat of the sun. Low rainfall levels caused by the rain shadow effect occur in the western edges of continents leading to drier inland conditions. As moisture laden winds are carried over coastal mountain ranges, the cool air condenses leading to rainfall on the windward side.Once precipitation has occurred the air is much drier inland leading to deserts such as the Sahara becoming increasingly dry. High pressure belts at 15 to 30 degrees latitude cause low levels of rainfall as dry cold air blows across the desert. SOILS The arid soils of the hot desert biome form due to the low levels of precipitation and high daytime temperatures and are the main soil type found in the biome. Most arid soils are gravelly as the lack of rainfall prevents chemical weathering. The large diurnal and extreme temperatures mean mechanical weathering is common with exfoliation breaking rock into scree. Fine particles of sand are blown away by strong winds leaving heavier particles behind. Low levels of precipitation and sparse vegetation, arid soils have high mineral content but little organic matter. Evaporation rates are much higher than precipitation rates meaning capillary action occurs as groundwater is drawn up through the soil. As water reaches the surface, it rapidly evaporates leaving large salt pans on the surface. Salinisation poisons the land and makes it toxic for most plants. Calcite sometimes forms on the surface if calcification occurs.This forms a hardpan that roots cannot penetrate. Most arid soils are unable to support widespread vegetation growth and do noy have well developed a horizons due to their lack of humus. Lack of vegetation restricts the soil building activities of microorganisms while the absence of organic matter also prevents rainwater from being retained. Flash floods occur during torrential downpours whicherode top soil and carry it down slopes forming a deposit of mud, gravel and sand at the base of valleys. FLORA Some plant species have adapted to survive in extreme heat and drought. Vegetation is sparse due to a shortage of water, high levels of evaporation, lack of humus and infertile soils. As water is scarce some plants have developed efficient root systems to maximise their ability to absorb rain and dew. Cacti have shallow roots which spread over a large area to collect moisture. By draining water and organic matter from close to the surface the roots avoid having to penetrate the calcium hardpans. Acacia trees have developed deep taproots to reach groundwater deep in the soil, reaching 6 to 7 metres below the surface. Ephemerals have adapted to take advantage of unpredictable desert rains. Their seeds have waxy coats that allow them to retain their moisture for long periods. They can lay dormant in the soil for long periods, sometimes years until it rains. When rainfall occurs they burst into life by germinating, growing , flowering and producing new seeds which allows the cycle to continue. Mouse ear cress is a good example. Succulents have developed ways to store water, for example cacti. They have vertical grooves that channel rainwater to the roots like a drain pipe. These channels also allow it to expand when water is plentiful. Needles protect it from being eaten and prevent moisture loss. It also has waxy skin to prevent moisture loss and acts like a sponge inside to store large amounts of water. FAUNA Some animals have adapted to survive in the desert. Insects, scorpions and spiders are the most common animals found in the desert. They can survive on very little food which makes them well adapted to desert conditions. Scorpions can survive for up to a year without food as they can slow down their metabolism and hibernate. They can come out of hibernation instantly if prey passes by and are extremely venomous, killing with one sting. Many animals have adapted to avoid the daytime heat by hunting at night like the jackrabbit and cactus pygmy owl. The pygmy owl actually lives in hollows carved out in cacti during the day in order to avoid intense heat. The camel has many physical adaptations to survive in the desert. They store fat in their hump which acts as a food reserve. It can also be turned into water during times of drought. They have 2 long rows of eyelashes which prevent sand getting in their eyes and coarse fur on their backs to protect them from intense sunlight. They have wide padded feet which allows them to walk on loose sand without sinking or getting burned.