22 WINTER 2015 ARBOR AGE www.arborage.com
INDUSTRY INSIGHTS
BY MICHELLE SUTTON
Sodium chloride (NaCl), the same salt that we use to season
our food, has been used to deice roadways and sidewalks since
World War II. It's cheap, and has made our roadways safer;
but its downsides are many, including damage to aquatic life,
infrastructure and our trees. Harm to trees results from NaCl
accumulation in the soil and/or from salt spray. When you salt
a slice of eggplant, you can observe how, via osmosis, water is
drawn out of the cells. Salt desiccates trees in the same way.
Soil salinity and salt spray damage plants in different ways.
In clay soils, salt can contribute to soil compaction because of
the way salt molecules bind with clay particles. Compaction
reduces the ability of water and oxygen to move through soils
and be taken up by roots. Also, salt in the soil is taken up by
tree roots with myriad negative consequences — from failure
to leaf out to marginal leaf necrosis. By contrast, salt spray
most commonly kills buds, resulting in twig or branch dieback
or "witches broom," which occurs when side shoots emerge to
compensate for apical bud death.
Many environmental groups and municipalities are seeking
alternatives to NaCl — from potassium chloride to urea to
beet juice. Dr. Glynn Percival, plant physiologist and technical
support specialist at the Bartlett Research Laboratory in
Reading, U.K., has researched and published papers on many
facets of salt damage. (Surprisingly, given the extent of damage
NaCl can do, Percival has very few colleagues doing this kind
of research). As to NaCl alternatives, Percival said, "There
Protecting Trees against the
Ravages of Deicing Salt
PHOTO
BY
MICHELLE
SUTTON
Marginal leaf necrosis/"burn" can be caused by soil salinity or salt spray.
