DESERT BIOMES

DESERT – AN AREA WHERE EVAPORATION EXCEEDS

PRECIPITATION

DESERT BIOMES SPARSE, WIDELY SPACED, MOSTLY LOW

VEGETATION PRECIPITATION IS LESS THAN 25 CM (10

INCHES) PER YEAR COVER ABOUT 30% OF THE EARTH’S

LAND SITUATED MAINLY BETWEEN TROPICAL

AND SUBTROPICAL REGIONS NORTH AND SOUTH OF THE EQUATOR

DESERT BIOMES LARGEST DESERTS ARE IN THE

INTERIORS OF CONTINENTS AIR THAT HAS LOST ITS MOISTURE

OVER THE TROPICS FALLS BACK TO EARTH

DESERT WARMS DURING THE DAY QUICKLY LOSES HEAT AT NIGHT

BECAUSE OF LITTLE VEGETATION AND MOISTURE AND SKIES ARE CLEAR

3 TYPES OF DESERTS TROPICAL DESERTS – TEMPERATURES

ARE USUALLY HIGH YEAR-ROUND LITTLE RAIN ONLY 1-2 MONTHS EACH

YEAR TYPICALLY HAVE FEW PLANTS AND

HARD, WINDBLOWN SURFACES STREWN WITH ROCKS AND SOME SAND

SAHARA DESERT IN AFRICA

3 TYPES OF DESERTS

TEMPERATE DESERTS – DAYTIME TEMPERATURES ARE HIGH IN SUMMER AND LOW IN WINTER

PRECIPITATION OF 8-12 INCHES EACH YEAR

MAY – AUGUST HAS MOST RAIN

TEMPERATE DESERTS SPARSE VEGETATION – MOSTLY OF

WIDELY DISPERSED, DROUGHT-RESISTANT SHRUBS AND CACTI OR OTHER SUCCULENTS

ANIMALS ARE ADAPTED TO THE LACK OF WATER AND TEMPERATURE VARIATIONS

MOJAVE DESERT IN S.W. CALIFORNIA

COLD DESERTS

GOBI DESERT IN CHINA COLD WINTERS WARM OR HOT SUMMERS 7-13 INCHES OF RAIN EACH YEAR

SEMIDESERT

SEMIARID ZONES BETWEEN DESERTS AND GRASSLANDS

DOMINATED BY THORN TREES AND SHRUBS

PLANTS ADAPTED TO LONG DRY SPELLS FOLLOWED BY BRIEF, SOMETIMES HEAVY RAINS

DESERT SURVIVAL

PERENNIAL SHRUBS SUCH AS MESQUITE AND CREOSOTE PLANTS GROW DEEP ROOTS TO TAP INTO GROUNDWATER

DROP LEAVES TO SURVIVE IN A DORMANT STATE DURING LONG, DRY SPELLS

HOW DO DESERT PLANTS AND ANIMALS SURVIVE?

SOME DESERT PLANTS ARE EVERGREENS WITH WAX-COATED LEAVES THAT MINIMIZE TRANSPIRATION (CREOSOTE BUSH)

DESERT PERENNIALS HAVE SMALL LEAVES OR NO LEAVES WHICH HELPS THEM CONSERVE WATER

DESERT SURVIVAL OTHER PERENNIALS SUCH AS PRICKLY

PEAR AND SAGUARO CACTUS USE WIDELY SPREAD, SHALLOW ROOTS TO COLLECT WATER AFTER BRIEF SHOWERS AND STORE IT IN THEIR SPONGY TISSUES

HAVE SHARP SPINES TO KEEP HERBIVORES FROM FEEDING ON THEIR WATER-STORING, FLESHY TISSUE

DESERT SURVIVAL SPINES ALSO REDUCE OVERHEATING BY

REFLECTING SOME SUNLIGHT SPINES PROVIDE SHADE AND

INSULATION CREOSOTE BUSH AND SAGEBRUSH

SECRETE TOXINS INTO THE SOIL TO REDUCE COMPETITION FOR WATER AND NUTRIENTS FROM OTHER PLANT SPECIES

DESERT SURVIVAL

MANY DESERT PLANTS ARE ANNUAL WILDFLOWERS AND GRASSES THAT STORE MUCH OF THEIR BIOMASS IN SEEDS DURING DRY PERIODS AND REMAIN INACTIVE UNTIL THEY GET ENOUGH WATER TO GERMINATE

DESERT SURVIVAL

MOSSES AND LICHENS CAN TOLERATE EXTREMELY HIGH TEMPERATURES

THEY DRY OUT COMPLETELY, BECOME DORMANT UNTIL THE NEXT RAINFALL

HOW DO DESERT ANIMALS SURVIVE?

MOST DESERT ANIMALS ARE SMALL SURVIVE THE HEAT AND REDUCE

WATER LOSS BY EVAPORATIVE COOLING

STAY IN COOL AREAS BY DAY COME OUT AT NIGHT OR EARLY

MORNING

HOW DO DESERT ANIMALS SURVIVE? PHYSICAL ADAPTATIONS: INSECTS & REPTILES HAVE THICK

OUTER COVERINGS TO MINIMIZE WATER LOSS THROUGH EVAPORATION

REDUCE WATER LOSS BY HAVING DRIED FECES &

EXCRETING A DRIED CONCENTRATE OF URINE

HOW DO DESERT ANIMALS SURVIVE?

SPIDERS AND INSECTS GET THEIR WATER FROM THE DEW OR FROM THE FOOD THEY EAT

SOME DESERT ANIMALS BECOME DORMANT DURING PERIODS OF EXTREME HEAT OR DROUGHT AND ARE ACTIVE ONLY DURING THE COOLER MONTHS OF THE YEAR

WHAT IMPACTS DO HUMAN ACTIVITIES HAVE ON DESERT ECOSYSTEMS?

RAPID GROWTH OF LARGE DESERT CITIES

IRRIGATION OF SOME DESERT AREAS TO GROW CROPS – AS THE WATER EVAPORATES, SALTS MAY ACCUMULATE IN TH SOIL AND LIMIT CROP PRODUCTIVITY

DEPLETION OF UNDERGROUND WATER

HUMAN IMPACTS ON DESERTS DISRUPTION AND POLLUTION BY

EXTRACTION OF OIL, MINERALS AND BUILDING MATERIALS SUCH AS ROAD STONE AND SAND

USE OF REMOTE DESERT AREAS AS SITES FOR STORAGE OF TOXIC AND RADIOACTIVE WASTES, UNDERGROUND TESTING OF NUCLEAR WEAPONS AND MILITARY MANEUVERS

HUMAN IMPACTS ON DESERTS

DESERTS TAKE A LONG TIME TO RECOVER FROM DISTURBANCES BECAUSE:

SLOW PLANT GROWTH LOW SPECIES DIVERSITY SLOW NUTRIENT CYCLING WATER SHORTAGES

HUMAN IMPACTS ON DESERTS THE LARGEST AND MOST UNTAPPED

RESOURCE OF DESERTS IS THE ABUNDANT SUNLIGHT

IF SOLAR ENERGY IS USED MORE IN THE NEXT 50 YEARS, LARGE AREAS OF DESERTS WILL BE COVERED WITH SOLAR COLLECTORS AND SOLAR CELLS WHICH WILL DISRUPT THE DESERT ECOSYSTEMS