Saturday, April 22, 2017

Urban Root Management: Big Infrastructure, Small Space, Stressed Roots


Summary: Urban root management defends six species-specific root types in three climate-specific root systems against infrastructural intrusions into small spaces.


Urban root management looks for symptoms of stressed roots, such as buttressing; buttress root injury to Wye Oak, largest white oak in the United States, toppled during thunderstorm June 6, 2002; Wye Mills, Talbot County, Eastern Shore of Maryland: Randy Cyr/Greentree/Bugwood.org, CC BY 3.0, via Forestry Images

The article Root Management: An Introduction for the April 2017 issue of Arborist News assigns at least one non-structural or structural kind of root to all the world's conifers, hardwoods and palms.
Conifers and hardwoods as dicots and palm trees as monocots bear roots to absorb minerals and water, anchor and support trees, produce hormones and store carbohydrates. Urban root management considers interactions with infrastructure, plants, property and soil, site usage and tree health, longevity and stability in compacted space and infrastructural conflict contexts. Tree health and mature size depend upon root space size and soil quality whereas root type number and size display variability by soil conditions and species.
Urban trees rarely entertain tap roots, first seed-released root, first axis for other roots, seedling stage's deep mineral- and water-absorbing, dominant, gravitropic (vertically oriented), tapering root.

Absorbent, anchoring, horizontal, near-surface, ropelike, untapered lateral roots fit between fine terminal roots and, below damage-prone root collars or trunk flares, the trunk's rapid taper zone.
Wind loading generates buttress roots, or lateral roots with buttressing, as wood tissue on upper unions between laterals and trunks whose bases grapple with mechanical stress. Anchoring, branching, diagonally downward-growing, mineral- and water-uptaking heart or oblique roots at below-ground trunk bases, between lateral and tap roots, have smaller diameters than tap roots. Urban root management identifies drip lines from trunks to outermost branch tips as below-ground occurrences of absorbent, anchoring sinker roots inclining vertically downward from lateral roots.
Continually replaced, multi-branching, near-surface, omnidirectional, relatively short-lived fine roots 0.002 to 0.07 inches (0.05 to 1.78 millimeters) in diameter juggle origins from all other root types.

Fine roots keep tree crowns and root systems balanced and, with symbiotic fungal colonies of mycorrhizae, fungal pathogen threats lower and mineral and water uptake higher. They lack the group status of adventitious, lateral, oblique, sinker and tap roots as structural roots that lend anchorage or support to the tree canopy crown.
Lower trunks in contact with moist soil or organic matter, palm trees, secondary tissue of older roots and vegetatively propagated tree cuttings muster adventitious true roots. Their mineral and water absorption and their structural support after fine, lateral, oblique, sinker losses from injury, pruning or soil environment changes nurture mature tree health.
Urban root management obtains lateral and heart, or tap, root systems respectively more and less frequently on species native to semitropical, temperate and tropical climate zones.

Heart or oblique root systems predominate on woody species native to arid, Mediterranean and semi-arid climate zones while tap root systems with laterals prove least common.
Soil environment qualifies as the greatest determinant of root system depth and spread, with a deep, uniform soil-dwelling, heart root system-tending species oblique-rooting in shallow soils. Its compacted, hardpan, subsurface clay, decreased oxygen diffusion, high water tables and increased bulk density result in asymmetrical, non-uniform horizontal and vertical root development and spread. Its upper foot (30.48 centimeters) around palm tree trunk root initiation zones sustains adventitious roots that support no secondary growth for annual rings or increased diameters.
Urban root management tracks impacts of compacted spaces and intrusive infrastructures upon species-specific root systems, according to co-authors Larry Costello, E. Thomas Smiley and Gary Watson.

Urban root management considers soil environment, including presence of compaction, as most critical determinant of tree root system's depth and spread; compacted soil and high pH in parking lot island account for nutrient deficiency's effect on below-ground roots; Virginia Tech campus, Blacksburg, southwestern Virginia: Mary Ann Hansen/Virginia Polytechnic Institute and State University/Bugwood.org, CC BY 3.0, via Forestry Images

Acknowledgment
My special thanks to:
Talented artists and photographers/concerned organizations who make their fine images available on the Internet;
Virginia Polytechnic Institute and State University for superior on-campus and on-line resources.
Image credits:
buttress root injury to Wye Oak, largest white oak in the United States, toppled during thunderstorm June 6, 2002; Wye Mills, Talbot County, Eastern Shore of Maryland: Randy Cyr/Greentree/Bugwood.org, CC BY 3.0, via Forestry Images @ https://www.forestryimages.org/browse/detail.cfm?imgnum=1238350
Urban root management considers soil environment, including presence of compaction, as most critical determinant of tree root system's depth and spread; compacted soil and high pH in parking lot island account for nutrient deficiency's effect on below-ground roots: Mary Ann Hansen/Virginia Polytechnic Institute and State University/Bugwood.org, CC BY 3.0, via Forestry Images @ https://www.forestryimages.org/browse/detail.cfm?imgnum=5334097

For further information:
Costello, Larry; Watson, Gary; and Smiley, E. Thomas. April 2017. "Root Management: An Introduction." Arborist News 2(2): 12-18.

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