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Home , Great Basin Desert, Sonoran Desert

Final Exam Carbon Cycle Web Sites…. • Thurs May 11h 11-1 Koffler 204

• Vehicle C emissions and wind credits: • 100 multiple choice questions http://www.participate.net/terrapass – Cumulative – ~10-15% will be on Natural History of the Sonoran • Carbon quiz: • You already have a study guide (outlines and key http://www.wired.com/wired/archive/14.05/carbon.html concepts) • Review session: Wed the 10th 11 AM Koffer 204

Natural History of the Sonoran Natural History of the Desert 1. What is a desert? 2. Desert and desert habitats 3. Adaptation in (generally) 4. and animals of the Sonoran Desert

Connections between the detail of the Sonoran Desert and general concepts you have been learning

What is a desert? What is a desert? • Communities are a continuum • Deserts: – dry places with virtually no life • Tucson Basin ‘moist’ ends of desert – National Park that’s teaming with plant life • We don’t need to worry too much about • Deserts are extremely hot, others not where the exact cut-off point is on the continuum (except that we live in an ‘iffy’ desert)

1 What is a What is a desert? desert? • Rainfall alone doesn’t capture aridity • Also – how easily water is lost by plants A dry place with drought adapted plants and Potential Evapotranspiration (PET): how animals and an open canopy much water evaporates and is transpired Often defined by annual : from plant leaves when it is not limiting • Ecologists: < 125 mm An Index of aridity – evaporative strength of air • Ecologists: < 250 mm (Tucson has 300 mm! San Diego has the same The ratio of PET:Precip is what climatologists precip as Tucson) use to define a desert

What is a desert? Where is a desert? Ratio higher than 3 as semi-arid Primary determinants of where deserts are: Tucson – 300 mm precip/ 1,524 mm PET A. Sunlight falls perpendicular to the axis of the The air can evaporate 5x more water than spherical planet actually falls in precip – so even if we had B. 3 Laws of air and water: 1,524 mm of precip it could all be evaporated! 1. Hot air rises, cool air sinks 2. Rising air expands and cools, sinking air For comparison: compresses and heats up Yuma PET/P = 30 3. Warm air can hold more water than cool PET/P = 600 air

Where is a desert? Where is a desert?

• Warmest in tropics – • Creates convection near vertical sunlight cells - Hadley Cells • • Hot air rises from • Rising air spreads towards the poles the tropics, cools, and drops in • Eventually cools and then sinks, flowing storms back toward the surface • Air sinks around 30 degrees N and S

2 Where is a desert? Where is a desert? Thus deserts are found mostly at 30 degrees N • Cool air sinks Æ Can it hold more or less water? and S latitude • No rain AND absorbs moisture

Where is a desert? There are 4 North American Deserts Desert – northern most, highest Rain shadows exacerbate the dryness of the elevation. Very cold winters (in the Old World desert Southwest – would be called a steppe)

There are 4 North American Deserts There are 4 North American Deserts – Summer growing season – winter rain. Hard freezes (but isnt always rain!) Many species of low shrubs & winter annual Small leaved shrubs. Poor in trees, succulents plants (only seen in wet years) Few and annuals. succulents and trees Dominants: big sagebrush (Artemisia) Joshua tree is a tree yucca

3 There are 4 North American Deserts There are 4 North American Deserts – high elevation and Sonoran Desert – Biseasonal rainfall. air causes winter freezes. Northern 2/3 gets winter storms, southern 2/3 gets summer Many species of low shrubs, leaf succulents, thunderstorms and small cacti. Few trees. • The only NA desert with mild Summer rainfall – summer annuals winters (only a few hard freezes) • Allows tropical plants and animals to edge up here • Dominants: legume trees and columnar cacti. (Also many shrubs and annuals)

There are 6 Subdivisions of the Subdivisions of the Sonoran Desert Sonoran Desert Lower River Valley Hottest driest part of the desert 1. Lower Valley 2. Upland • Temperature: just like in the Mojave 3. Plains of – Over 120 F (49 C), soil temperatures to 180 F (82 C) 4. Central Gulf Coast • Rainfall: low as 76 mm (3 in) but doesn’t rain every 5. Vizcaino year 6. Magdalena Plains

Subdivisions of the Sonoran Desert Subdivisions of the Sonoran Desert Lower Colorado River Valley Lower Colorado River Valley

Valleys: creosote bush and white bursage Mountains – have more shrubs and cacti (Very drought tolerant perennials) Few columnar cacti (they are restricted to valley • Trees grow along larger washes floors) 50% or more of the plants are annuals, mostly winter annuals, and abundant only in wet years

4 Subdivisions of the Sonoran Desert Subdivisions of the Sonoran Desert Arizona Upland Arizona Upland Highest, coldest part of the Sonoran Desert • Hard frosts exclude some species found in other • More trees and succulents parts of Sonoran Desert • Trees on rocky slopes and drainageways • Two equal rainy seasons • on slopes above valley floors • Palo Verde is a common tree

• Many plants and animals – 630 plant species in the alone

Subdivisions of the Sonoran Desert Subdivisions of the Sonoran Desert Vizcaino Vizcaino • Pacific side of Baja • Many stem succulents: Boojum (Fouquiera • Less than 125 mm rain, but humid breezes and columnaris), Baja elephant tree (Pachycormus fog discolor), strangler figs

Subdivisions of the Sonoran Desert Vizcaino Desert Adaptation Concepts • Also Blue Palms (Brahea armata) The main stressors are aridity and heat: •Aridity? water is needed for physiological functions (e.g. photosynthesis, transport)

• Heat?

5 Desert Adaptation Concepts Desert Adaptation Concepts • Heat – Van’t Hoff’s Rule for every temperature rise of 10o C, rate of Options? biochemical reactions double (up to a point) 1. EXPIRE: when the going gets tough…die – Have annual lifecycle and be a tough egg/seed This is why it is bad to get too hot or too cold during harsh times – Too cold = body functions slow due to Van’t Hoff’s Rule. e.g. annual wildflowers – Too hot = proteins break down and body functions slow

Desert Adaptation Concepts Torpor: a resting state • lowering of body temp below activity temp Options? 1. EXPIRE • Reduces water needs – less evaporation, less respiration, less excretion 2. EVADE: when the going gets tough…avoid – Store Water. Example: • Also reduces energy needs – – Spatial – migrate, select comfortable – Slower heat loss microhabitat – Less tissue demand (Van’t Hoff’s Rule) – Temporal – nocturnal, CAM, torpor

Endure: Temperature Desert Adaptation Concepts Stress

Options? 1. Reduce Heat Input 1. EXPIRE Ex. Use orientation/posture, shading from spines/hairs, small surface area 2. EVADE 3. ENDURE: when the going gets tough, tough What’s going on with the toes? it out. Several adaptations: – Temperature Stress – Water Stress

6 Endure: Water Stress Endure: Temperature Stress

1. Store Water 1. Reduce Heat Input • Animals – in fatty deposits 2. Dissipate Heat Ex. Small size, long extremities, evaporative cool • Plants - roots, stems, and/or leaves of plants (plants that 3. Tolerate Hyperthermia (High do this are called Body Temp) succulents) Ex. C4 photosynthesis, Harris’ Antelope Squirrel (up to 105 F!)

Endure: Water Stress Endure: Water Stress

2. Conserve Water 3. Tolerate Dehydration • Minimize loss through skin • Many plants (prickly pear) e.g. waxes, small surface area and animals (desert toads) • Minimize excretory loss can tolerate great losses of concentrate urine, dry feces water without dying • Minimize respiratory loss C4/CAM photosynthesis, e.g. Humans: ~12% loss drought deciduous leaves, torpor Prickly pear: ~80% loss

Notable Plants and Animals Notable Plants and Animals Ambrosia – major cause of hay fever Ambrosia • Different Species are very common throughout Drought deciduous shrubs the Sonoran desert • Avoid drought by loosing leaves in hot, dry season •Critical nurse plants • Usually have 2 leaf cohorts per year – monsoon and cool winter • Downside: it takes several weeks to re-deploy their leaves (the photosynthetic machinery)

7 Notable Plants and Animals Notable Plants and Animals Ambrosias vary in leaf size and drought tolerance • Smaller leaves, divided leaves - smaller Larger leaves have more photosynthesis and boundary layer and loose heat more can evaporatively cool (need plenty of water effectively by convection to keep stomata open) • Don’t overheat Boundary layer of stagnant air at the surface and can overheat when stomata are closed Which type of leaf do you think is the most drought tolerant (large vs. small)?

Notable Plants and Animals Notable Plants and Animals Ambrosia ambrosiodes - Canyon Ragweed – Triangleleaf bursage • A large broadleaf shrub • Shrub with smaller leaves • Confined to washes and canyon bottoms – • Same range as canyon ragweed, but is on • Where it can get enough water to plains evaporatively cool • Dominant plant in Arizona Upland (with the Palo Verde and Saguaro)

Notable Plants and Animals Notable Plants and Animals - White Bursage Defining life forms of the Sonoran Desert: • Small shrub with smallest leaves • Columnar Cacti and Legume trees • Dominant in driest areas of the Lower • Columnar cacti are found in arid tropical Colorado River habitats throughout , Central and • Leave size matches aridity of habitat • 41 Species in Mexico

8 Notable Plants and Animals Final Exam There’s 4 big ones in the Sonoran Desert: • Thurs May 11h 11-1 Koffler 204 • Cardon • 100 multiple choice questions • Senita – Cumulative • Organ Pipe – ~10-15% will be on Natural History of the Sonoran • Sagauro Desert • You already have a study guide (outlines and key concepts) • Review session: – Michod Tues 9th 1PM location TBA – P-Z and Hunter Wed the 10th 11 AM BSE 100

ExI ExII ExIII Total Exam III – Natural History of the Sonoran 94 96 96 286 Top score 98 Desert 96 94 96 286 Mean 75 92 96 98 286 98 92 96 286 Mean top points so far: 282 out of 300 (roughly 94) 94 96 94 284 So (roughly): 100 90 92 282 A: 253-282 92 94 96 282 B: 225-252 98 92 90 280 C: 197-225 92 94 92 278 D: 155-197 98 94 86 278 E: <154

Notable Plants and Animals Notable Plants and Animals Saguaro CAM succulents (like Saguaro) have shallow but • The only columnar cactus cold- extensive root system hardy enough to grow in the • 4 in deep & extend out as far as the plant is tall Arizona Upland • Largest cactus in the USA

9 Notable Plants and Animals Notable Plants and Animals

CAM metabolism ‘idles’ during It never really goes dormant drought • Can resume full growth 24-48 hrs after rain Close their stomata – • Recycle CO2 to photosynthesis • Recycle O2 to respiration • Uses shallow roots and idling photosynthesis to take advantage of frequent small

Notable Plants and Animals Notable Plants and Animals

• Only under nurse plants do they get protection • Takes several wetter than from temperature, average years drought and predators • Only occurs several times a century in the AZ Upland • Grow very very slowly = there is episodic recruitment

Notable Plants and Animals Notable Plants and Animals

The Sonoran Desert is dominated by Palo Verde - stem photosynthetic trees columnar cacti and legume trees • 72% of growth is from stem photosynthesis Legume trees: Palo Verde, Mesquite, • More chlorophyll in stems than leaves Ironwood • More photosynthesis with less water loss (higher WUE)

10 Notable Plants and Animals Notable Plants and Animals Photosynthetically active all year – but drought Ocotillo – Fouquieria deciduous Drought deciduous C3 plants that behave like • Produces leaves only in response to heavy CAM plants rains • Intermediate in function between drought avoiding deciduous shrubs and drought resistant evergreens

Notable Plants and Animals Notable Plants and Animals • Short shoots allow rapid leaf deployment Invasive grasses are threatening the Sonoran • Very shallow roots allow rapid uptake Desert • Behaves like a CAM plant (but is C3) e.g. Bufflegrass (Pennisetum ciliare) was • Idling - parenchyma layer under the bark, extensively introduced to AZ and Sonora for but no stomata livestock forage since the 1960s Expanding along highways and is invading the desert

Notable Plants and Animals Notable Plants and Animals • In Sonora more than 1,000,000 hectares of desert Bark Scorpion have been purposely converted to Bufflegrass • Most poisonous of the 30 in AZ • ‘Grassification’ of the desert • Not likely to kill a human (but it sure hurts) • Results in drastic habitat reduction and reduction • Orients upside down (people often get stung in species diversity picking up rocks) • It is big and burns easily • Strong venom paralyzes prey

11 Notable Plants and Animals Notable Plants and Animals Giant Hairy Scorpion Giant desert centipede () • Biggest in the USA – 6 inches! • True giant at 6-8 in long • Uncommon, only out a few weeks in summer • Aposematic coloration – • Eats what ever it wants! • Mild venom (it doesn’t need much!) • Bite is painful but not dangerous to humans • Won’t bite if you don’t pick them up

Notable Plants and Animals Notable Plants and Animals Kissing bugs – our local Bees nightmare • Tucson has more species of bees • 1 in long Bloodsuckers than anywhere else in the world: • Fly around in May and June • Sonoran Desert: 1,000 species in 45 genera in 7 families • Inject anesthetic and an • Bees are the pollinators of most anticoagulant desert plants • Wake up with a large hard itchy welt

Notable Plants and Animals Notable Plants and Animals Most bees in the Sonoran Desert dig burrows in Tarantula hawk – a wasp the ground for their brood • Huge – 2 inches Most are solitary • Very painful sting • Tarantula is eaten alive by larvae A few bees are social Honey bees and bumble bees are highly social, they have queens that are larger than the workers

12 Notable Plants and Animals Notable Plants and Animals Rattlesnakes • Fangs are like retractable hypodermic • 11 species of rattlesnakes in Sonoran Desert needles • Usually diurnal • Hemolytic venom - breaks down blood and • “Extra” senses: vessels, useful for subduing prey and beginning the digestive process – Pit organ: ‘heat vision’ – Jacobson's Organ: augments smell

Notable Plants and Animals Notable Plants and Animals Rattlesnake bites are NOT always fatal Bats – 25% of all mammals are bats • Eat lots of insects. You are more likely to die in a car • Pollinate flowers and disperse seeds for accident than from a snakebite ecologically and economically important Most rattler bites are ‘dry’ plants. • Protect Gotham City from criminal elements. • Many are threatened or endangered. Most rattlesnake bite victims are young men - bitten while handling the snake. Called “illegitimate” bites.

Notable Plants and Animals Notable Plants and Animals

California leaf-nosed bat can live for months Lesser long-nosed bat - feed on nectar of without water. columnar cacti. • Large eyes as good as the best military • Migratory – follow the flowering of cardon and night vision goggles. organ pipe north in late spring. • They pluck tiny sleeping insects from foliage • Feed on agave at higher elevations during the without even landing. summer. • Don’t migrate • Return south feeding on agaves in the fall.

13 Notable Plants and Animals Notable Plants and Animals Coevolved relationship with cacti: Hummingbirds - birds with: • Plants provide copious nectar at night. • Most iridescent colors. • Light colored flowers with strong musty odor • Fastest wing beat (80 beats per second). • Sturdy flowers arranged for easy bat access. • Fastest heart beat (500/min. resting, 1260 • Bat has long slender snout with extensible flying). tongue with a brush tip for lapping nectar. • World’s smallest species (< 2 gm).

Notable Plants and Animals Hummingbird Metabolism • Eat mostly nectar and insects. • It requires lots of energy to be a hummingbird (fast heart and wings, high body temp:105-109F). • It’s like driving a car with a one-gallon gas tank: constant need to refuel. • They consume 70% of body weight in solid food per day, 4-8 times their body weight in H2O.

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