From the SelectedWorks of David A Bainbridge

Winter 2020

DEEP ROOTS MATTERDavid A Bainbridge

This work is licensed under a Creative Commons CC_BY International License.

Available at: https://works.bepress.com/david_a_bainbridge/63/

David A. Bainbridge Restoration Ecologist

Deep Roots Matter

Vadose Zone Phreatic zone

Root lives matter

• Most of the time we ignore our roots • We can’t see them • We don’t know them • But they are important

Mycorrhizal fungi• Roots also support fungi

• The fungi help bring water and nutrients in to the root

• They can connect plants - sharing water and nutrients

• A cubic meter of soil may have 600 miles of hyphae

• 20-50 times smaller than a human hair

• Roots and hyphae can add up

Interconnection• Connections may be critical in arid

environments

• Mature trees can help support seedlings

• Here is a connection map for two species of fungi from an older oak tree to other plants

• As far as 60 feet away from host

Hyphae as root aids

• The threads of hyphae act as micro-roots

• They can collect and move water and nutrients

• Small enough to penetrate tiny cracks in many rock types - even granite

• Critical in arid zones • Here an oak tree root with hyphae

Mike Allen UC Riverside

How deep?

• Live mesquite roots have been found close to 200 feet deep

• Torrey pine roots reach 75+ feet

• Shepherd’s Tree 223 feet Namibia desert

• Acacia erioloba 197 feet

• Statue of Liberty is 151 feet tall

Root studies

• I studied roots of mesquite seedlings in the low desert

• They are adapted to germinate after a flood event and to stay ahead of the drying front

• Dominant tap roots go deep fast

• I also learned that digging in the desert soil can lead to Valley Fever - a lung disease from fungi

Field

Tap root• Note the vigorous growth • Few minor roots • Maximum root growth was at

108°F for Velvet Mesquite

Seedling

Two years

Deep studies• Hand auger 15 feet max (student power)

• Drilling rig, samples 20+ feet

• Rhizobia and mycorrhizal fungi

• Nematodes and other critters

• Groundwater

M. Darby MS Thesis work near Mecca, CA

Professor Ross Virginia UC Riverside

Lab studies

• Roots are easier to study in the lab • A soil filled clear plastic film tube • Resting in a gutter section • The tube is shaded • Rotated to measure growth

Root races

Fast tap rootsMany species could grow rapidly

Carob Oak

12

AllocationRoots not shoots

• Roots matter

• Shoots are less critical

• Root:shoot ratio mesquite 5:1 - 10:1

• Most forest trees in temperate areas are more likely 1:3 or even 1:5

• Nursery plants are often 1:20

• Guided development of new containers

SOIL SURFACE

CM

Root-Shoot• Few good studies of roots

• Difficult and Costly

• Many fail to go beyond 2 or 3 feet

• The global average here was for all good studies the researchers could find

• Mesquite estimates by author, after Geesing and Felker

Lab simulations• Nitrogen fixation in the damp soil

above the water table

• 15-20+ feet

• Simulated deep roots in tall sections of pvc pipe in the greenhouse at UC Riverside

• Research by Professor Virginia and colleagues

Ross Virginia mesquite root studies

Lessons learned• Deep containers needed to grow tap root

dominated desert plants • Historically lath box or bamboo split • PVC pipe split • Bob Moon at Joshua Tree developed Tall

Pots (32” x 6”) • Stuewe and Sons make several excellent

containers

MS Thesis near Mecca - Marcy Darby

Deep containers

• Plastic sleeve tube

• Planting demo - Arizona 1987

• Narrow plastic pipe for deep irrigation

• Later explored in greater detail

• Look on line “Deep pipe” irrigation

Tall Pots• Effective but costly • Easier to handle than sleeves • Challenging to transport, plant

Joshua Tree Native Plant Nursery

Tall potAnza Borrego Desert

• Excellent survival

• Rapid growth

Tall Pots

Later we cut many down to 16” and

called them half-highs

Deepots• Inexpensive • Can be used for deep pipe irrigation after planting • Tippy so build rack or pack boxes

carefully

stuewe.com(541) 757-7798

Roots•Pay attention to the whole plant •Soil texture, composition and moisture

all affect root growth •Make the right soil mix for your species •Don’t overwater •Deep irrigation •Consider adding site collected rhizobia

and mycorrhizal fungi when planting (or in nursery)

Eight years P. glandulosa

Root studies

• Lab and greenhouse • Digging • Installing access tubes with holes • Video logging from transparent tubes • Radioactive tagging • But many studies are needed to better

understand carbon allocation • Hydraulic lift of roots

Root studies in Thailand

Maeght

Needed• Better tools for

root studies

• More funding for root research

• More studies of soil ecosystems

Reading Roots• Böhm W. 1979. Methods of Studying Root Systems. Springer, Berlin

• Maeght, J. L., B. Rewald and A. Pierret. 2013. How to study deep roots—and why it matters. Frontiers in Plant Science. 4(299):1-14.

• Bainbridge, D. A. 2007. A Guide for Desert and Dryland Restoration. Island Press.

• Allen, M. F. 2007. Mycorrhizal fungi: highways for water and nutrients in arid soils. Vadose Zone Journal. 6(2):291-297.

• Virginia R. A., M. B. Jenkins, W. M. Jarrell. 1986. Depth of root symbiont occurrence in soil. Biology and Fertility of Soils. 2:127–130.

• Eilers K. G., S. Debenport, S. Anderson and N. Fierer. 2012. Digging deeper to find unique microbial communities: the strong effect of depth on the structure of bacterial and archaeal communities in soil. Soil Biology and Biochemistry. 50:58-65.

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