Subtropical Deserts

Deserts are areas of low rainfall and high evaporation rates and cover about ¼ of the Earth’s surface. Contrary to common perceptions, most deserts are not sandy, nor are they populated with succulent cacti. The deserts of the world tend to be dominated by perennial grasses and annuals.

Climate

Arid climates that fluctuate temperatures throughout the day and the seasons

Rainfall

Precipitation is the abiotic factor that mostly defines this biome
Very little rainfall
- Rainfall tends to come all at once in a short period, causing temporary flooding
Less than 25 cm/yr

Temperature

Extreme fluctuations in temperature between months and even day to night
Desert can occupy average annual extremes: -10° to 30°C
- Hot deserts occupying the lower righthand portion of the graph
- Cold deserts occupy the lower middle portion of the graph
- Notice that the desert biomes occupies a broad temperature range at the bottom of the Whittaker graph (right)

Above: A Whittaker Graph showing where deserts occupy this abiotic space, based on precipitation and temperature. Notice that a lack of rainfall defines a desert, but not the temperature, since there are cold and hot deserts.

Types

Hot & dry deserts

Seasons are generally warm throughout the year and very hot in the summer. The winters usually bring little rainfall.
Annual average temperatures: 20-25° C
e.g., Chihuahuan, Sonoran, Mojave, and Great Basin of the United States, as well as the Sahara and Arabian deserts

Semiarid deserts

Summers are moderately long and dry, and like hot deserts, the winters normally bring low concentrations of rainfall
Summer temperatures usually average between 21-27° C, and evening temperatures are cool, at around 10° C
Condensation of dew caused by night cooling may equal or exceed the rainfall received by some deserts
e.g., Utah, Montana, and the Great Basin

Coastal deserts

Deserts found along the edge of oceans, but receive little precipitation due to wind patterns
e.g., Atacama desert in Chile, and the Namibian desert

Cold deserts

These areas have cold winters with snowfall and large rainfalls widely during the winter and occasionally over the summer
The mean winter temperature is -2-4° C, and the mean summer temperature is 21-26° C
Cold deserts and tundras can sometimes be viewed as synonymous, but subtle differences can be noted
- Tundras are usually covered in small plants and have many small streams and ponds during the melt of summer.
- A cold desert will have very few streams or ponds, and very few plants.
- e.g., Antarctica interior, Greenland, and the Nearctic realm

Soil

Abundant nutrients, but water is limited for absorption
The common desert soil types are aridisols (dry and deficient in organic matter
Most deserts are not sandy, except the Saharan and Arabian deserts
n.b. "desertification" is a process by which fertile top soils are damaged by over-farming or over-grazing, resulting in increasingly dry and infertile land (e.g. Dust Bowl in the 1930s Midwest; modern impacts on the Sahel of Africa)

Regional Expressions

southwest North America, Namibia, southern Argentina, north and south Africa, middle east, central Australia, mountains of Asia

Flora

Desert flora exhibit many adaptations to this biome
Some adaptations to store water and prevent evaporation, but most desert plants (>85%) do not show structural adaptations to conserve water. (Gibson 1998)

Annuals

Short life spans, appearing after seasonal rains
Seeds lie dormant for a majority of the year

Geophytes

Plants that have underground storage organs, with ephemeral above-ground portions for photosynthesis and reproduction
e.g. bulbs, corms, rhizomes, and tubers

Grasses

Well adapted to dry conditions with bulliform cells and C4 photosynthesis

Deciduous shrubs

Similar to a temperate deciduous forest, shrubs in the desert drop leaves before the dry season begins

Evergreen shrubs

Some shrubs, such as creosote bush (Larrea tridentata)

Phreatophytes

Plants with deep taproots, to access the water table

Succulent perennials

Less than 15% of plants in deserts are cacti (Gibson, 1996)
In the United States, only the Sonoran Desert has abundant cacti, including the Saguaro cactus (Carnegiea gigantea), which is endemic to that desert.
Worldwide, only in the Karroo of South Africa and the Atacama Desert of South America, there are large percentages of stem-succulent plants in the landscape.

Above: Woolly tidestromia (Tidestromia lanuginosa) in the Sonoran desert

Above: the saguaro cactus (Carnegiea gigantea), which is native to the Sonoran desert of North America

Evolution of the biome

It is assumed that arid land, with desert-like conditions, has been on Earth since early in its history, similar to a Mars-like landscape
Due to limited water, deserts do not preserve evidence well, and therefore fossil evidence for deserts is limited
Evidence for plants living in desert biomes appears in the Permian, but may have occurred earlier

Additional Resources

Lab-grown cyanobacteria remove microplastics from water (Univ. of Missouri 2Feb2026)

└Remediation and upcycling of microplastics by algae with wastewater nutrient removal and bioproduction potential (Long et al, 2025)

Restoring ecosystem function can reverse desertification in Europe's drylands (Pensoft Publishers 31Jan2026)

└Restoring Function, Reviving Resilience: Practical Solutions for Desert Ecosystem Recovery

Organisms in the Atacama Desert soil are remarkably diverse (Univ. of Cologne 13Jan2026)

└Geographic distribution of nematodes in the Atacama is associated with elevation, climate gradients and parthenogenesis (Villegas et al., 2026)

Combining ecological restoration with climate-resilient agriculture to tackle desertification (Phys.org 7Jan2026)

└Strategies reimagined: SDG-driven solutions for combating global desertification (Wang et al, 2025)

Scientists found the most heat-tolerant plant on Earth hiding in plain sight (ZME Science 5Jan2025)

└Photosynthetic acclimation is a key contributor to exponential growth of a desert plant in Death Valley summer (Prado et al., 2025)

Desert microbes drive soil carbon sinks in arid regions (Phys.org 28Nov2025)

└Long‐term fate of photosynthetic carbon in desert plants: microbial necromass‐driven pathways for soil carbon stabilization (Cong et al., 2025)

Desert ecosystems emerge as frontiers for carbon sequestration and climate action (Phys.org 11Nov2025)

└Desert ecosystems as carbon frontiers: innovations in sequestration and climate adaptation strategies (Islam et al., 2025)

Death Valley shrub rearranges its insides to thrive in one of the hottest places on Earth (LiveScience 20Nov2025)

└Photosynthetic acclimation is a key contributor to exponential growth of a desert plant in Death Valley summer (Prado et al., 2025)

Joshua trees face climate threat despite heat adaptation (Phys.org 8Sep2025)

└Heyduk et al. (2025) Cryptic CAM photosynthesis in Joshua tree (Yucca brevifolia, Y. jaegeriana)

Researchers uncover molecular mechanisms of desiccation tolerance in desert moss (Phys.org 2Sep2025)

└Yin et al. (2025) Phosphoproteomics analysis provides novel insight into the mechanisms of extreme desiccation tolerance of the desert moss Syntrichia caninervis

Snow algae accelerate Antarctic ice shelf melting (Phys.org 27Aug2025)

└Liang et al. (2025) Seasonal cycles of snow algal blooms intensify surface melting on Antarctic ice shelves

California approves an unprecedented plan to protect Joshua trees from climate change threats (LA Times 18Aug2025)
Jewelflowers seek friendly environments rather than adapt (Phys.org 1Jul2025)

└Bontrager et al. (2025) Herbarium specimens reveal a constrained seasonal climate niche despite diverged annual climates across a wildflower clade

Snow cloaks Atacama, the world's driest desert (Phys.org 27Jun2025)
Desert plants' clever survival trick: Two dormancy cycles a year ensure survival in harsh conditions (Phys.org 19Feb2025)

└Guo et al. (2025) Semiannual dormancy cycling results in two seedling cohorts of annual species in the cold desert of Central Asia

With CO2 Levels Rising, World’s Drylands Are Turning Green (Yale Environment 360, 16Jul2024)
In the World’s Driest Desert, Ancient Wisdom Blooms Eternal (NY Times 3Nov2023)
Atacama Desert Blooms in 2015
6,000 years ago the Sahara Desert was a tropical grassland (Texas A&M 2016; Nature GeoScience 2016)
The Mighty Saguaro (In Defense of Plants, 2018)
What survives in the Atacama Desert? (NY Times 10May2023)

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