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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.
• More information at: www.bepress.com/david_a_bainbridge/