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Planting vegetation is an effective way to increase dune stability.
The root networks of plants hold sand in place to reduce erosion.
The stems, leaves and blades of grass slow down wind near the ground
to reduce erosion and trap wind-blown sand.
Planting native
species is advantageous because the species are well-adapted
to dune conditions and produce a naturally-functioning system. For
example, Ammophila breviligulata (commonly known as American
beach grass or marram grass) is a pioneering dune plant that thrives
in areas of active sand movement and deposition. The beach grass
is a natural dune builder because it tolerates hot, dry sand conditions,
it traps moving sand, it sends shoots up through growing sand deposits,
and it spreads horizontally by rhizomes.
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All the beach grass in this photo was planted 7
months earlier. This is a harsh environment--the upper windward
slope of a large parabolic dune--but the woody debris traps some
sand which is helping the beach grass survive.
(North Beach Park parabolic dune in May 2005.) |
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Planting non-native species occurs where speed of stabilization
(rather than restoration or conservation) is the motivating factor.
Some coastal homeowners plant exotic species because they see dunes
on their property as an extension of their landscaping. Sometimes
coastal managers introduce species that have been successful in
stabilizing dunes elsewhere in the world. Ammophila arenaria
(European beach grass) was introduced to the United States
west coast where it has both outcompeted the native Ammophila
breviligulata and changed the shape of coastal foredunes.
Afforestation,
or foresting dune areas, has a long history of use as a method of
stabilizing dunes. In Europe and North America, most plantings occurred
between 1920 and 1960. Pplantations of conifers (mostly pine and
spruce) remain on many coastal dunes. The conifers almost completely
destroy native vegetation within a couple of years because of progressive
shading and deposits of relatively inert needles on the forest floor.
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