Tropical Deserts By: Neil Mehta Drew Overcash Brendon Esperancilla

Deserted [di-zur-tid] (adjective): abandoned; forsaken unfrequented; lonely without inhabitants or life High temperatures and dry conditions. Subtropical latitudes (15°-30°) Mostly near equator South America, Africa, and Australia

Climate Dry (arid and semiarid) climate zone Temperature Rainfall Average 22.8°C (73.04°F) Can rise to over 45°C (113°F) Rainfall Less than 43.8 mm annual precipitation Lack due to drying high pressure systems and rain shadows

Formation: High pressure systems Mountain rain shadows Subtropical ridge (intense drying effect) Mountain rain shadows

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High winds can cause disturbances such as dust devils (actually pretty dangerous), sandstorms, and formation/migration of sand dunes. Monsoon – a seasonal prevailing wind that lasts for months, carries heat (and also moisture)

Low biomass (look around!) Least productivity of every biome Few photosynthetic or chemosythetic organisms If there are many plants, then animal life will be abundant Plants need sunlight, nutrients, warm temperatures, and water

Dry soil Low water, high mineral content Lack of leaching gives more fertility than in rain forest Plants adapted to these conditions exist in the desert Shrubs, succulents, shallow root plants, etc.

Cactus “Succulent” (thick, reduced, “succulent” leaves) Minimizing surface area (smaller leaves) decreases area available for water loss Thick, waxy coat layer improves water retention Spines shade the cactus and defend against animals seeking water

CAM plants Fix CO2 at night, store it as malate (acid), released during day (Rubisco improves efficiency) Allows plant to keep stomata closed during the hot, dry day to conserve water C4 plants Store CO2 as a 4-carbon (C4) organic acid at night Like CAM, allows plant to conserve water C-4

Animals Reptiles, insects, birds, and mammals Reptiles: thick, scaly skin protects from sun, heat, and water loss Insects: chitinous exoskeleton helps prevent water loss Most sleep/shelter during the worst heat of the day Some never drink but get water from seeds, some obtain water from plants like cacti Kangaroo rat: does not drink water and eats primarily seeds Survives mostly on water produced during metabolism

Threats Mining can lead to salinization of soil Overgrazing/deforestation can allow deserts to spread Off-road vehicle use Tumbleweed Non-native and invasive (sound familiar?)

Credit File:Sahara satellite hires.jpg File:Kangaroo-rat.jpg Music: “Gritzy Koopahari” by username: saintedix