By Germer Aguilar and Nik Wolek P.2 The Tropical Desert By Germer Aguilar and Nik Wolek P.2

Location of Biome

Abiotic Factors Precipitation- Sporadic periods of rain; Some deserts can get up to 10 inches of rain annually. Water availability- Lack of rainfall, but contain groundwater very deep in the sand Sunlight- Due to lack of humidity and tall plants, deserts get a lot of sunlight. Temperature- Can vary from scorching hot during the day to freezing cold at night Sand Dunes- Dunes can rise up to 500 feet.

Biotic Factors Kangaroo Rats: South-western deserts of the U.S. Turpentine bush Lizards Worms, Beetles Hawk, Fox

Climate Underneath the sand, the soil is very high in salinity. In simpler terms, the soil is very salty. The tropical desert has the highest mean annual temperatures of any climate on Earth (120 degrees Fahrenheit). This is due to high sun angles throughout the year and lack of shade from tall plants. At night, the temperature can drastically drop to below fifty degrees Fahrenheit.

Climate Graph

NPP Net Primary Productivity: very low when compared to other biomes The Net Primary Productivity of tropical deserts are typically under 200 kilocalories per square meter per year.

Succession Primary succession could occur on sand dunes, where bacteria/seeds find a microclimate that offers a pocket of increased moisture and protection Deserts are capable of undergoing secondary succession However, due to the harsh conditions and soil salinity, deserts take the longest amount of time to recover from a disaster such as a fire, flash flood, etc.

Flow of store of Nutrients/Nutrient Chart Gershmehl model of Tropical Desert’s flow of nutrients

Habitats Some habitats are short-lived; which results in evolutions that help animals and plants adapt to such extreme conditions. When habitats do develop, it is usually after rainfall occurs. Climate change is melting many glaciers that provide freshwater to some desert communities.

Niches Open desert scrub Open grasslands Washes and sandy soils.

Food Chain

Food Web

Energy Pyramid

Biomass Pyramid/ Trophic Levels A pyramid of biomass is a more accurate indication of how much energy is passed on at each trophic level.

Pyramid of Numbers A graphical representation of the number of individuals in each population in a food chain.

Biodiversity: Animals Kangaroo rats: They don’t sweat/pant. Coyotes: True omnivore diet in that they eat just about anything available

Biodiversity: Plants Plants have adapted by developing long roots to reach hidden groundwater. Saguaro Cactus: Located in Arizona, it can grow over 24 appendages and up to 2 feet in diameter. Their long appendages are filled with water. Bur Sage: Bush that spreads seeds through the fur of passing animals. One of not many seeds able to survive in hot/sunny areas such as the tropical desert. Creosote Bush: Has dry/waxy leaves that absorb moisture exceptionally well and fend off the heat. Cactuses: They protect the water they retain using prickly needles.

Human Activity Trenching for underground pipelines in deserts creates large amounts of unusable land that will take decades to return back to its natural form. Off-Roading in deserts such as the Moab has led to scars in the soil which has a negative effect on the vegetation there. Many military exercises are conducted in open stretches of desert however this leads to pure destruction of land and leaves hundreds of acres destroyed at a time.

Case Studies Climate changes have caused deserts to expand and take over previously tropical/grass land. As shown below the Sahara Desert has nearly tripled in size in the past 4000 years.

Case Studies (cont.) Deserts create nutrient-rich soil, and releases phosphorous which is carried in winds and fertilizes many areas. Scientists have found that phosphorous from the Sahara has been “fertilizing” the Amazon Rainforest.

Comparison/Contrast Although it is taking up previously usable land, the desert is still providing many nutrients for other biomes to thrive. In both case studies the nutrients provided by the desert are spreading. The expansion of the desert is still taking over previously usable land which is negative however the second case study provides evidence of the positive effects of the nutrients the desert spreads.