Restoring the Savanna Understory
Once the site has been
cleared of undesirable woody vegetation, the next step is to re-establish
the groundlayer vegetation.
If the site has not been grazed in many
years
Some “good” savanna species will probably have returned and will
begin to flourish once the understory has been opened up. However,
the species diversity will almost certainly be low, so it is essential
to initiate a detailed program of seed collecting and planting.
The process here is called “overseeding” or “interseeding.”
After all the undesirable woody vegetation has been removed, begin
annual burning followed by handplanting with a good mix of savanna
understory species. Burning followed by seeding must be repeated
for yearly. Since fall planting is usually best, burn in the fall
and then plant. Burning will eliminate oak leaves and open up the
ground so that planted seeds can reach the mineral soil.
Plant savanna specialist species, as many kinds as possible. (For
Seed Mixes, see this link) Some species can be planted throughout,
but in especially sunny or shady areas plant species better adapted
to those habitats. Plant savanna grasses in patches or swaths rather
than uniformly throughout. If only small amounts of seeds of certain
species are available, plant those in favored locations.
If the understory has been recently grazed
In this case, there will probably be no desirable understory left.
The routine here is to kill all the existing vegetation with one
(or several years) of heavy herbicide treatment, and then plant.
Use a heavy herbicide treatment to destroy whatever groundlayer
is present and start from scratch. This is the approach that prairie
restorationists use on agricultural land.
See this link for details of how the site can be prepared for planting.
Seed collecting and planting
A vital part of savanna restoration is bringing back the diversity
of plant species in the understory. This
is so important that details are given in a separate section.
Here we just present an outline of what is involved.
How many species to plant? The diversity of species in the understory
of an oak savanna is higher than in either a prairie or woodland
in the same area. This is because the savanna has elements of both
prairie and woodland as well as a suite of species that are unique
to the savanna. The more species, the better. However, not all species
should be planted uniformly over the whole area. The savanna environment
is very heterogeneous, and some areas are more prairie-like and
others are more woodland-like.
Steps
in planting for savanna restoration
• Make up a species list
• Collect and clean seeds of the target species
• Make up seed mixes
• Burn the savanna so that bare areas are available for planting
• Plant by hand broadcasting.
• Monitor in future years
Lists of species for savannas have
been discussed in other sections.
Seed collecting and cleaning, and
planting are discussed in other sections.
Seed mixes for savannas
The specifications of a seed mix consider both the list of species
to be planted, and the seeding rate. Seeding
rate is specified as number of seeds per square foot, or the pounds
of seeds per acre.
Because of the variability of the savanna environment, a single
seed mix generally cannot be used throughout the whole planting
unit. At a minimum, three separate seed mixes should be considered
for a single site:
• A prairie seed mix for the completely open areas of the savanna
• An open savanna mix for the areas with partial shade. Here the
canopy might range from 20 to 60%.
• A closed savanna mix for those areas with more dense canopy, grading
into woodland.
Details of seed collecting and planting
are given in another section.
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Planting
the understory of a white oak savanna. This cleared area had
been burned a few days before. |
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