Melaleuca Lockdown In Loxahatchee
The
Loxahatchee Slough Natural Area is a 12,000-acre mosaic of wetlands,
pine flatwoods, cypress swamps and wet prairies on the northeastern edge
of the Everglades in Palm Beach County, Fla. It provides the largest
area of habitat for threatened Florida sandhill cranes and other wading
birds. Endangered snail kites and wood storks also call the Slough home,
along with many other threatened species of birds and reptiles.
This
exceedingly rare ecosystem is threatened by the spread of melaleuca —
an invasive tree species that grows up to 80 feet tall, creating a dense
monoculture that has overtaken wildlife habitat and altered water flow
through the region.
An Ecosystem Interrupted
From the
laundry list of mini-ecosystems interspersed throughout the Everglades,
it might seem there is room for virtually any plant. But according to
Todd Olson of Aquatic Vegetation Control, Inc. (AVC), there is no room
for invasive species like melaleuca.
"Melaleuca in particular is a
problem species in the Slough. The root systems in melaleuca
monocultures can quickly create dry land in knee-deep water," he said.
"This disrupts the overall hydrology by changing the way the sheet of
water moves through the slough."
Pitching In For the Long Haul
Frank
Griffiths is the leader of the Palm Beach County team fighting to
protect the Slough. He and other members of the Palm Beach County
Department of Environmental Resource Management developed a five-year
restoration plan that includes removal of 780 acres of melaleuca and
other invasive plants.
"We have two primary goals for the
restoration of the Slough," said Griffiths. "We want to reintroduce fire
into the ecosystem to help native plants thrive, and we need to control
and remove invasive species from the area."
One important partner
in the plan is Olson and his team from AVC. Griffiths chose AVC partly
because of its standing as a Quality Vegetation Management™ (QVM)
Certified Applicator.
Vegetation management professionals who are
QVM Certified strive to go above and beyond in their duties as
vegetation managers to restore and improve habitat while protecting
threatened and endangered species. They also engage in advanced
technical training to ensure they are applying herbicides responsibly,
in a way that benefits the environment being treated.
AVC has
developed creative strategies to access some of the more remote areas of
the Slough. Merely reaching stands of melaleuca in these remote areas
can be as challenging as keeping the plants under control. "Over the
course of the restoration program, we've had to fly crews into treatment
sites on more than one occasion," said Olson. "In other cases,
prescribed burns have helped us gain access to remote areas that were
otherwise inaccessible."
Choose Your Weapon
According to
Olson, much of what determines the control method relates to the
melaleuca tree diameter and whether an infestation has completely taken
hold. In areas with only a sparse population of seedlings, hand-pulling
is an option for control. But as the monoculture fills in and grows
tall, spraying melaleuca is the best first step.
"If the trees are
greater than four inches in DBH [diameter at breast height], we use a
frill and girdle technique to treat melaleuca," said Olson. "We remove
the paper bark to expose the cambium in a three to five-inch band around
the tree, and treat the exposed area with a Habitat® herbicide solution
with MSO [methylated seed oil]."
For areas where trees are less
than four inches DBH, cut-stump treatments using the same amount of
Habitat can be used. Vast monocultures may be treated with a helicopter
foliar application of Habitat and Rodeo®, plus a surfactant.
Treatments
are completed in a "target" pattern, moving from the outer edges of
infestation to the inner cores. This method cuts off further expansion,
and creates a trackable pattern for future treatments.
Holding the Line
A
one-time spray treatment will not eliminate a stand of melaleuca. It
takes several seasons of working a comprehensive plan to get the job
done.
"After the first spray, melaleuca releases millions of
seeds, and getting the mature trees out of the way actually gives the
seedlings more of what they need to flourish," said Griffiths. "We
maintain all the outlying areas in the target pattern as we work inward,
so treatments are cumulative."
Treatments include mechanical
removal of the largest tree skeletons and/or chipping tree litter in the
densest monoculture areas.
Until the trees have been removed,
prescribed burning isn't an effective tool for Slough management.
Melaleuca is well adapted to fire; it burns extremely hot and adult
trees typically are only charred. This means the adult trees have an
opportunity to reseed before native plants, which are often destroyed by
the hotter fires fueled by the large trees.
However, after the
areas are opened, prescribed burning can be effective. When conducted
properly, the fires burn off competing vegetation and encourage new
growth that wildlife can use for food.
"When it comes to restoration in the Loxahatchee Slough, we're in it for the long haul," said Griffiths. "Working with great herbicide applicators like AVC and following our long-term plan can make a real difference for endangered wildlife and our diverse ecosystem."