Selecting Trees for Drought Resilience

Larry A. RuppUSU Extension Landscape Horticulturist

Resilience• The ability to spring

back; elasticity• The capacity to

recover quickly from difficulties; toughness

Why is drought an issue?

Trees lost in Texas drought 300 million wild trees 5 million urban trees

California drought – irrigation restrictions

Utah drought – political ramifications

Your livelihoods are at stake

Utah’s answer to drought?

www.bbburma.net

My impressions of Nevada trees

Montello

Winnemucca

How do trees use water?

“Water loss is driven by atmospheric demand, limited by the available soil moisture reservoir, and modified by plant anatomy and physiology” -Clark and Kjelgren, 1990

The Paradox

Trees must open their stomates to obtain CO2

Water is lost through open stomates

What happens in drought?

• Soil drying• Drought stress occurs when soil moisture drops

enough that growth and transpiration is inhibited

• Water uptake decreases• Water potential becomes more negative

throughout the tree

What happens in drought?

• Tissues dehydrate• Stomata close • Cavitation of water columns

• Results• Less photosynthesis• Direct damage due to cavitation, membrane

failure, organ shedding, etc.• Susceptibility to secondary damage

• Insect• Frost• Disease• More drought

Effects of Drought

Effects of Drought

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

Stomatal control

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Reduce leaf temperature• White, silver, or reflective leaves• Smaller leaflets• Reduced leaf surface area• Incised margins

Small, revolute leaves

Reduced surface area

Small, incised leaves

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Reduce leaf temperature

3. Altered leaf surfaces• Thick cuticles• Waxy coatings• Scales or hairy coverings

Waxy coatings

Scales or hairs

From Lai, Kratsch, and Kjelgren

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Reduce leaf temperature

3. Altered leaf surfaces

4. Reduced leaf area1. Long-term adaptations

2. Leaf shedding

Reduced leaf area

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Reduce leaf temperature

3. Altered leaf surfaces

4. Reduced leaf area

5. Change leaf orientation

Leaf orientation

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Reduce leaf temperature

3. Altered leaf surfaces

4. Reduced leaf area

5. Change leaf orientation

6. Develop xylem that resists cavitation

How do trees manage water loss?

1. Reduce water use 1. Adjust leaf water potential by closing stomates

to limit transpiration (which also limits photosynthesis)

2. Increase available water• Keep stomates open to maximize

photosynthesis• Use energy to search for more water

Phreatophytes

Roots

• Extensive root systems with lots of fine roots are critical to avoiding drought• Deep• Fibrous• Rapid production of new roots

Pine versus Spruce: Pine had 24 times as many root branches and tips and 8 times the absorbing surface.

- Nobbe

Competition

Finding resilient trees

Look for characteristics of drought tolerant plants

Finding resilient trees

Look for plants native to dry environments

Remember there are always exceptions to

rules

“Many xeric plants have adapted not to use water efficiently, but to survive drought” - Tipton, 1994

Single-leaf Ash

Bald Cypress

How much water does a tree really need?

Must keep the big picture in mind.

Can drought resilience be negative?

• Invasive, highly competitive plants• Salt cedar• Russian olive

Resources for Finding Drought Resilient Trees

Your Collective Experience

What do you think are the best trees for drought resilience in Nevada?

Links

AbCoAcGiAcTaAcGrAcNeAiAlCaSpCerCaCerOcCerLedCelLaeCelOccClKeCoObCrDoCuArElAnFrAn

FrPeGiBiGlTrGyDiJuMaJuOsJuScKoPaMaSppMoAlPiChPiEdPiFlPiHePiJePiLoPiPuPiMo

PiNiPiSyPoDePoTrPrViPyCaQuGaRoAmRoPsSoJaTaDiTaRaUlPaUlPuZeSeEnd

Resilient Evergreens

Pinus monophyllaSingle-leaf Pinyon

Pinus edulisPinyon Pine

Juniperus osteospermaUtah Juniper

Juniperus scopulorumRocky Mountain Juniper

http://www.landmarklandscapes.us/plants-database/evergreen-trees

Rocky Mountain Juniper ‘Skyrocket’

Cupressus arizonicaArizona Cypress

Cercocarpus ledifolius

Curl-leaf Mountain Mahogany

Pinus sylvestrisScots Pine

Pinus nigraAustrian Pine

Pinus jeffreyiJeffrey Pine

Pinus flexilisLimber Pine

http://japanesemaplesandevergreens.com/store/product/pinus-flexilis-vanderwolfs-pyramid-4-year-graft

Limber Pine ‘Vanderwolf’s

Pyramid’

Pinus heldreichiiBosnian Pine

Pinus longaevaWestern Bristlecone Pine

Abies concolorWhite Fir

Taxodium distichumBald Cypress

Picea pungensBlue Spruce

http://www.twinspringsnursery.com/Picea.html

Blue Spruce ‘Fat Albert’

Resilient Deciduous Trees

Koelreuteria paniculataGoldenraintree

http://www.ayearinseattlegardens.com/ Paul S. Drobot

Gleditsia triacanthosHoneylocust

ISU Forestry Extension

Gymnocladus dioicusKentucky Coffeetree

Acer grandidentatumBigtooth Maple

Acer tataricum Tatarian Maple ‘Hot Wings’

Hoernursery.com

Acer ginnalaAmur Maple ‘Flame’

Quercus gambeliiGambel Oak

Quercus buckeyeTexas Red Oak

Quercus muhlenbergiiChinkapin Oak

• Sawtooth• White• Swamp white• Shingle• Bur• Pin• English• Shumard

Celtis occidentalisHackberry

Celtis laevigata var.

reticulataNetleaf

Hackberry

Catalpa speciosaNorthern Catalpa

www.chicagobotanic.org

Prunus virginianaChokecherry

Chokecherry ‘Schubert’

Winchesternursery.com

Chokecherry ‘Canada Red’

Powellgardens.com

http://www.americansouthwest.net/slot_canyons/white_canyon/white-canyon1_l.html

Cercis occident

alisWestern Redbud

David A. Hoffman

Cercis canadensisEastern Redbud

Zelkova serrataJapanese Zelkova

Bruce Marlin, Wikimedia

Ginkgo bilobaGinkgo

Pyrus calleryanaCallery Pear

Ulmus parvifoliaChinese Elm (Lacebark Elm)

Onlineplantguide.compublic.asu.edu

Cladrastus kentuckiaYellowwood

Sophora japonicaJapanese Pagoda Tree

Pistachia chinensis

Chinese Pistache

Malus sppCrabapple

Juglans majorArizona Walnut

Cotinus obovatusSmoketree

Crataegus douglasiiBlack Hawthorn

Crataegus ambiguaRussian Hawthorn

Resilient Trees with Caveats

Torres, Wikimedia

Ailanthus altissimaTree of Heaven

Tamarix ramosissimaSalt Cedar

Carter, et. al., www.mdpi.com

Eleagnus angustifoliaRussian Olive

Patrick Breen, Oregon State University, Bugwood.org

Paul Wray, Iowa State University, Bugwood.org

USU Extension

Morus albaWhite Mulberry

Bioimages.vaderbilt.edu

Robinia pseudoacaciaBlack Locust

Robinia × ambigua ‘Idahoensis’Idaho Flowering Locust ‘Purple Robe’

Davisla.wordpress.com

Robinia neomexicanaNew Mexican Locust

http://www.waterwiseplants.utah.gov/

Fraxinus pennsylvanicaGreen Ash

Fraxinus anomalaSingle-leaf Ash

Ulmus pumilaSiberian Elm

Populus tremuloidesQuaking Aspen

“Adapted to the heat, drought and humidity of the Midwestern prairie, this Nebraska native brings lowland adaptability and disease tolerance to a high elevation favorite. Introduced by Schmidt in cooperation with the Nebraska Statewide Arboretum, Prairie Gold® greatly expands the planting range of this mountain species.” - J. Frank Schmidt Nursery

http://www.springgrovenursery.com/picture/prairie-gold-aspen-tree-fac.jpg?pictureId=13445065

Quaking Aspen ‘Prairie Gold’

Acer negundoBoxelder

FlamingoVariegated cream and green leaves with a touch of pink. Worth considering, but does revert to wild-type on occasion.

Boxelder ‘Flamingo’

Willows and Cottonwoods

Points to Remember Right tree – right place means less

maintenance and less resources (water) Resources to find the right tree

USU Tree Browser Dirr Manual

Avoid monocultures

Natives are not a panacea

Natives can help create a ‘Western’ landscape ethic

Questions or Comments?

Water use by trees

https://www.youtube.com/watch?v=BickMFHAZR0