FLORIDA PARK SERVICE
ANNUAL REPORT
District 4 Research
Park:
Oscar Scherer State Park
Date:
September 30, 1995
Project:
Wire Grass Restoration in Mesic Flatwoods, OSSP-9-OD
Researcher: Samuel A. Cole, Biological Scientist I
(Assisted by Volunteer Any Peters)
Abstract -- From September 1993 to April 1994, park staff and volunteers transplanted
2,648 wire grass plugs from a dry prairie site in Northwestern Hardee County to a 13-acre
study site on former improved pasture on the Oscar Scherer State Park C.A.R.L. Addition.
Plugs were dug on a total of 9 monthly trips and planted at a density of 2.78 clumps/m2
over 9 plots measuring 12-m by 12-m. A few plots were manually watered on the day of
transplanting with 400 gallons of water. A 2-year schedule of monthly and quarterly
monitoring for wire grass survival was established. survival was gauged relative to
daily rain-fall and to a prescribed burn in June 1994. Survival on any 1 plot ranged
from 0% to 88% by July 1995. Data showed a sharp drop in survival between February and
May 1994, during a period of low rainfall. Plots transplanted as early as 5 months
pre-burn showed positive responses to burning. Monitoring during the second year
revealed that survival in all plots stabilized after the 1994 prescribed burn and remained
relatively constant. Monitoring during the second year revealed that survival in all
plots stabilized after the 1994 prescribed burn and remained relatively constant.
Monitoring is scheduled to continue until April 1996.
Introduction
Oscar Scherer State Park is located along South Creek, in the coastal region of
Sarasota County, about 2 miles south of Osprey, Florida (Figure 1).
The natural
communities that comprise this park include mesic flatwoods, scrubby flatwoods, prairie
hammocks, numerous depression marshes, and a fringe of tidal marsh (Florida Natural Areas
Inventory, Department of Natural Resources, 1990).
In 1991, the park acquired 922 acres through the C.A.R.L. program, tripling its
original size to 1,384 acres.
Many of the natural communities of this addition had been
altered considerably prior to acquisition by the state.
The principal activity was
cattle ranching on native range, and approximately 150 acres were converted to improved
2
pasture in 1984.
Here, native vegetation was cleared through cross-chopping and
planting for bahia grass (Paspalum notatum).
Pasture conditions were maintained in part
through prescribed burning by ranchers in 1987 and 1991.
Cattle grazing also continued
under lease until 1991 (Andy Peters, pers. comm.).
Restoration of the former mesic flatwoods that occupied this site is an important
resource management goal at Oscar Scherer State Park.
Without grazing pressure, many
native species of grasses, forbs and shrubs are evident on the pasture.
since
acquisition, prescribed burns-- 1 in December 1992 and the most recent in June 1994 --may
have further enhanced this native regrowth.
However, as beneficial as these efforts have been in reclaiming the site, it is
doubtful the 2 dominant understory species of flatwoods-saw palmetto (Serenoa repens)
and wire grass (Aristida beyrichiana [formerly A. stricta])--will return.
Hence,
restoration must involve planting techniques.
This pilot research project explores the efficacy of wire grass transplanting as
a method of mesic flatwood restoration.
During the late summer of 1993, an opportunity
for the "rescue" of wire grass from a donor site scheduled for large-scale clearing was
made available.
This site was a dry prairie in Northwestern Hardee county, approximately
63 miles from Oscar Scherer State Park (Figure 2).
Located near the Shirttail Branch
of Payne's Creek, a tributary of the Peace River, this 93-acre prairie was scheduled
for phosphate mining by CF Industries, Inc., beginning in the spring of 1994.
The Shirttail Branch site was managed by CF Industries for approximately 30 years
as qual range.
to maintain suitable habitat for hunting, the area was burned biennially
during the dormant season over this period, and as a result wire grass was abundant and
healthy.
The moving of a phosphate drag-line system into an area is a slow process,
and thus arrangements were made for park staff and volunteers to make monthly trips to
the prairie to dig up wire grass clumps, or plugs.
Although several monitoring strategies throughout the state have been employed
3
to gauge the effectiveness of rescue transplanting, to date there is no standardized
procedure for the removal and subsequent care of wire grass plugs.
Because time is often
a critical factor in any rescue, it is important to establish a rationale governing when,
how and even if transplanting should be carried out.
This study attempts to define an
efficient procedure for transplanting wire grass by monitoring survival rates of 2,648
transplanted plugs for a 2-year period.
This report covers the year immediately after the June 1994 prescribed burn, from
July 1994 to July 1995.
Excessive rainfall from June through August 1995 caused
extensive flooding throughout Oscar Scherer State Park and prevented access to most parts
of the C.A.R.L. addition.
during this period.
Therefore, no monitoring was conducted on the wire grass plots
Nevertheless, monitoring will continue through April 1996, the
2-year anniversary of the last transplanting.
STUDY SITE
Burn Zone 13 of Oscar Scherer State Park includes most of the 150-acre area
converted to improved pasture in 1984.
However, only a small portion of the zone has
retained the open-canopy, sparse shrub-cover character that distinguishes recently
abandoned pastureland.
elsewhere, the shade produced by a dense recruitment of slash
pines (Pinus elliottii) does not favor the transplanting of wire grass.
during the
summer of 1993 an area encompassing 13 acres of the eastern portion of the zone was
identified as the best site for potential wire grass research (Figure 3).
This site
was subdivided into approximately 470 blocks on which 12-m x 12-m (144-m2) plots could
be placed to receive wire grass plugs.
all plots for this project were randomly selected
and marked with PVC and rebar to establish locations permanently (Figure 4).
For ease
of access for watering, planting and monitoring, blocks were established so that no 2
sides or boundaries were in contact.
4
Burn Zone 13 is interspersed with several depression marshes and bordered on the
eastern side by scrubby flatwoods.
It is characterized largely by EauGallie and Myakka
fine sands, a soil typically associated with mesic flatwoods (Hyde, et.al., 1991).
Although its soils are different from the Pomona and Farmton fine sands of the donor
site (Robbins, et.al., 1980), the recipient appears similar in general habitat
characteristics.
The study site can be considered an artificial dry prairie, for most
of the slash pines have been removed.
Methods
From 25 September 1993 to 20 April 1994, a total of 10 Florida Park Service staff
and up to 18 volunteers participated in digging up wire grass from the donor site and/or
in planting and watering transplants at the recipient site.
Nine trips were made in
total, transporting from 125 to 414 wire grass plugs of various sizes for a total of
2,648 plugs on 9 plots.
October.
Trips were made once per month except for 2 trips mad during
For each trip, tracking forms were maintained for traveling time, digging time
at both sites and watering/planting time at the recipient site.
The total staff and
volunteer participation were also recorded, as well as total person-hours per trip.
Site-preparation treatments, such as disking or herbicide broad-casting, were not
attempted at the study site except for mowing the plots and digging the plug-holes just
prior to transplanting.
However, as equipment was available, fresh transplants were
manually supplemented with approximately 400 gallons of water per plot.
This watering,
done on the day of transplanting as a safeguard against excessive water loss, was the
only treatment given the plots after transplanting.
For most lots in this study, post-hole diggers were used to remove wire grass from
the donor site and to prepare the recipient site for planting.
Each plug was 4 to 5
inches in diameter, and 2 to 4 inches of soil were removed with each clump of wire grass.
5
Only younger clumps of wire grass were selected for transplanting.
May of the larger,
older clumps die in the center but expand vegetatively along the periphery.
Eventually
these clumps appear as a ring around the dead portion and eventually break up into smaller
clumps (Clewell, 1989).
This "ring" phenomenon was common at the Shirttail Branch site,
and older clumps were thus avoided to prevent excessive build-up of these dead centers
in plugs.
Site-preparation at the study site involved mowing to reduce the ground cover.
Although mowing may affect wire grass survival indirectly by favoring growth in the
surrounding bahia grass, this procedure allowed for greater efficiency in digging,
transplanting and initial monitoring.
After digging the plug-holes, the displaced bahia
grass sod was removed from the study site.
Transplants were placed in distinct rows, with each plug approximately 18 inches
away from neighboring plugs.
This allowed a maximum density of about 400 plugs per 144-m2
plot, or 2.78 plugs per m2.
This density is well under that actually measured on the
donor site (3.2 clumps/m2) (District 4 Annual Reports, X-1-D, 1995) and should allow for
future vegetative growth between plugs.
Many factors can influence wire grass survival, including soil saturation,
temperature, evapotranspiration and root competition.
It was felt that a pilot project
utilizing a high number of volunteers could be best implemented by monitoring a small
number of easily measured variables.
site and wire grass survival.
Two were selected:
precipitation at the recipient
Precipitation on the Shirttail Branch site may also
influence survival of transplants and was measured as a total of 16.5 inches (41.9 cm)
during the course of transplanting efforts (John Kiefer, pers. comm.).
This variable
should be investigated further.
Readings for precipitation on the study site were taken daily from the nearest
rain gauge, located at the park's shop complex.
This station is within 2 miles and is
considered and adequate indicator for rain on the pasture.
rainfall measurements are
6
totalled for each month, and then the average daily rainfall for that month is calculated
for comparison against wire grass survival.
Monitoring for wire grass survival on most study plots was conducted monthly for
the first 9 months after transplanting and then quarterly for the remainder of the study
period.
Each transplant was examined for the presence of green leaf tissue.
had green present were recorded as "alive" and flagged.
Those which
those without green were
recorded as "dead," and if the clump was previously marked as alive, the flag was removed.
Occasionally these "dead" plugs are actually alive--stress from transplanting,
low moisture and/or other factors may cause a die-back of above-ground tissues so that
the rootstock can conserve energy.
is alive.
Subsequent monitoring usually confirms if the plant
Survival was recorded as the percentage of flagged transplants to the total
number of transplants for a plot.
Because of the ambiguity in determining which
transplants are truly dead, it is possible for survival to apparently "increase" on a
plot.
As mentioned previously, Zone 13 was burned by park staff late in June 1994.
Because wire grass is adapted for frequent fire, it was determined that fire would not
be excluded from the study plots.
burned during this exercise.
Indeed, for all plots 90-100% of the transplants were
The timing of this burn was critical because it may allow
a determination of the fire-stress threshold for newly transplanted wire grass.
the plots varied form 2 to 9 months in age.
By June
For similar projects in northern Florida,
fire-passage proved fatal to most wire grass plugs if it occurred within 6 months after
transplanting (Greg Seamon, pers. comm.)
Results
Figures 5, 6 and 7 summarize survival on each plot monitored from September 1993
until July 1995.
Each Figure compares the average daily rainfall of this period (the
7
histogram portion) with survival on plots transplanted during a specific interval (the
line graph portion).
All curves begin (in the upper graph) at 100% survival for the
month of transplanting for each plot.
Each Figure also marks with a vertical line the
prescribed burn occurring on 20 June 1994.
All plots monitored during this month were
checked prior to the burn, on 15 June, to minimize inaccurate survival readings for that
month.
Figure 5 tracks survival for plots transplanted during September and October 1993.
Average survival for these 3 plots after the first quarter (November) was 95%.
After
the second quarter (February) it had fallen to 75%, and after the third quarter (May),
to 67%.
44%.
The first post-burn monitoring (July) recorded a drop in average survival to
For the year after this post-burn drop in survival, quarterly monitoring has
revealed that survival curves have virtually leveled off, with only slight increases
in survival on each plot.
By April 1995, the last monitoring to date for this subset,
average survival was 54%.
This subset of plots has the highest average survival rates out of the 3 subsets.
Moreover, 1 plot in this subset (#457) had a 1-year survival of 71% and a 2-year survival
of 88%, the highest survival for any of the 9 study plots.
Plot #457 is also the first
plot transplanted in this project, and it has the largest plug size.
Figure 6 tracks survival for plots transplanted during November and December 1993
and January 1994.
average survival after the second quarter (February) was 92%; after
the third quarter (May), 85%; and after the last quarter (August), just after the June
burn, 51%.
of data:
The second year's monitoring shows the same trend observed in the first subset
some "recovery" was noted for about 2 months following the prescribed burn,
and then the survival curve leveled off to approximately 52% by May 1995, the last
monitoring for this subset.
These values are moderate when compared to the same values for the other 2 subsets.
Plot #131, containing 5-month old transplants, showed a remarkable "increase" in survival
8
(from 31% to 48%) during the first 2 months post-burn.
This plot is also noteworthy
because transplants during the august 1994 monitoring visit were observed in
pre-anthesis.
is plot #85.
By May 1995 it had dropped slightly to 41% survival.
Equally noteworthy
Transplanted in November 1993, just as precipitation was rapidly
diminishing, it had a relatively strong survival rate.
Just before the June burn, 7
months after transplanting, survival was still over 80%.
The mortality rate seemed to
increase immediately following the burn, but post-burn "recovery" has maintained this
plot at 62%.
It cannot be determined from this data if the prescribed burn was a factor
in counteracting the effect of low rainfall during the spring months, but it probably
did not contribute heavily to the morality rate of the plot.
As of May 1995, its survival
is the highest of the plots in this subset.
Survival for the last 3 plots, transplanted during February, March and April 1994,
are tracked by Figure 7.
Average survival after the third quarter (May) was only 21%,
dropping to 6% after the last quarter (August), 2 months post-burn.
Although the
leveling trend noted previously holds for this subset during the second year, the average
survival is lowest in this group of plots, at 5% by May 1995.
The 2 last-planted plots, #129 and #3, were both recorded at 0% survival very
shortly after transplanting and have not recovered.
Hence, survival for this last subset
is best indicated by plot #287, which declined rapidly for the first 6 months of monitoring
to 17%.
During the last year this value has decreased only 2%.
The downward trend i n average survival on the 3 subsets during the first year
seems to follow the general precipitation pattern.
Generally, plots transplanted during
months receiving fair amounts of rain have survived well and moderately well.
Plots
transplanted during months receiving little rain have survived poorly.
This relationship is easily observed by tracking overall plug-survival, which
reveals low mortality until March 1994.
transplanted and 97.2% still survived.
By November 1993, 896 plugs had been
By February 1994, this total had grown to 1,706,
9
with a survival of 90.8%.
Only after this time did survival begin to plummet, with 1,447
plugs transplanted and only 54.6% still alive by May 1994.
At the end of the first year,
monitoring at 2 months post-burn revealed only 942 plugs, or 35.6%, of the project total
of 2,648 surviving.
This represents a cumulative mortality of 64.4%.
AFTER 2 years
of monitoring, total plug survival is at 33.0%, indicating a mortality of only 2.6% over
1 year.
It was proposed during the course of this study that the initial watering regime
of transplanted wire grass may be important to overall survival.
Therefore,
supplemental watering and precipitation during the first 5 days after transplanting was
monitored.
The results of this exercise are summarized by Figure 8.
As mentioned
previously, some plots were supplemented with approximately 400 gallons of water
immediately after transplanting.
Over a 144-m2 plot, this amount corresponds roughly
to 0.5 inches of rainfall, as indicated by the Figure.
In comparing the initial watering regime of Figure 8 with the survival curves of
the upper graphs of Figures 5, 6 and 7, no direct relationship can be inferred.
for
example, consider Plot #334, transplanted in October 1993, and Plot #287, transplanted
in February 1994.
Figure 8 indicates for the former an initial regime of 2 inches of
rainfall, and figure 5 depicts 10% mortality after the first month.
The corresponding
values for the latter are no rainfall or mechanical watering and 9% mortality (Figure
7) after the first month.
Long-term watering regimes, at least during the first year after transplanting,
do appear important.
Plot #334 was planted during one of the wettest periods of the
first year of study and was followed by a wet January 3 months later.
after transplanting, pre-burn survival had dropped 53%.
mortality rate of 6.6% per month.
By June, 8 months
This drop represents an average
Plot #287, conversely, was planted in one of the driest
periods of the year and was followed by an even drier May 3 months later.
4 months after transplanting, pre-burn survival had dropped 50%.
By June, only
Such a rapid drop
10
corresponds to an average mortality rate of 12.5% per month, almost double the rate for
Plot #334.
Conversely, watering regimes do not appear as critical during the second year after
transplanting.
Although the second year has received a much higher amount of
precipitation than the first (29.7 inches for September 1993 through July 1994 and 70.0
inches for September 1994 through July 1995), the rainfall patterns have been similar,
with wet summer and fall months and dry winter and spring months.
Yet, all the survival
curves during the second year reflect virtually no change once "recovery" was established
after the June 1994 burn.
The data gathered during this study does not allow a
determination on the role of precipitation after transplants have become established.
However, rainfall does appear to be more critical during the first year, when
transplanting stresses on wire grass are undoubtedly greater.
Discussion
Although successful rescue transplanting seems to be a function of the amount of
precipitation on the recipient site, many other factors may be important.
This study
concentrated on just 2 variables without excluding other influences which could have
contributed to plug mortality.
Future studies isolating variables such as competition
with bahia grass or other plants, differences in soil composition between sites and fire
stress may be helpful in more precisely defining the role of hydrology in wire grass
survival.
Because of the above limitations, this study can only suggest a target period during
which rescue transplanting should be attempted.
For southwestern Florida, the optimal
period should probably be during September through January.
prevented transplanting in the months of May through August.
The timing of this project
However, July and August
could probably be included in this window, based o the high levels of precipitation that
11
are usually observed during this season.
Rescue transplanting outside of the optimal window should be discouraged unless
long-term supplemental watering can substitute for lack of rainfall.
If this technique
is attempted beyond the window, long-term care of transplants should be maintained at
least through the first year, as indicated by the difference in the survival curves
between the 2 years of this study.
Excluding the time involved in setting-up and monitoring the plots, a conservative
total of 288 person-hours were recorded for this project.
Of this, because of the
distance involved, 195 person-hours were for travel to and from the Shirttail Branch
site.
The remaining 93 person-hours, a significant investment, were spend digging,
planting and watering at the donor and recipient sites.
by limiting rescue transplanting
to the wettest part of the year, high survival rates in wire grass may better justify
time spent on restoration using this method.
Rescue transplanting is only 1 means of restoration in wire grass ecosystems.
Other methods, such as nursery plugging and direct seeding, have met with great success
in some areas.
However, these other methods can be quite costly and occasionally
labor-intensive.
Research is underway to make these other methods more streamlined and
cost-efficient, but until that time, rescue transplanting may be a desirable alternative
in some cases.
Despite its efficiency, however, rescue transplanting is not a panacea for the
re-introduction of wire grass.
there are at least 3 considerations to explore before
attempting a rescue transplanting project.
and time-of-year, discussed earlier.
to the recipient.
The first involves local hydrological cycles
The second is the distance from the donor site
As can be seen from this pilot study, travel time can substantially
inflate the person-hours needed to accomplish the restoration objective.
also, the gene
pool of a population at a very remote location may be markedly different from local
populations.
fifty miles is generally accepted as the maximum desirable safe genetic
12
distance between populations, but adequate research in wire grass genetics is lacking
and this figure is unsubstantiated.
Finally, the third consideration concerns the scope of the restoration project.
Rescue transplanting as the sole restoration vehicle is appropriate only for small
projects, such as this pilot study or the reclamation of undesirable fire-lanes.
Although this method can be used to augment other techniques in large restoration
projects, the expenditure of time becomes astronomical if it is used as the sole
technique.
13
As a case in point, consider the 150-acre improved pastureland on Burn Zone 13
of Oscar Scherer State Park.
Assume the entire area is suitable for wire grass plugging
and 2.78 plugs/m2, or 400 plugs/144-m2, is the desired density.
Assume also that 16
person-hours, or 2 people working a full day, are required to retrieve, site-prepare,
transplant and water 400 wire grass plugs, roughly the equivalent of 1 truckload.
One
acre is equivalent to 4,048.33-m2, so approximately 38 plots 144-m2 in size would be
required per acre.
To restore the entire pasture, 4,200 plots would be needed.
This
translates to 67,200 person-hours, or 840 work-weeks if both people worked together every
day.
If the job proceeded without interruption, it would take approximately 16 years
for the 2 workers to restore the pasture.
If the restoration scope quartered the planting
density to 100 plugs per plot, or if the work force were quadrupled, it would still take
4 years of continuous labor to restore the area.
ACKNOWLEDGEMENTS
I am indebted to Oscar Scherer State Park volunteer Andy Peters for his hard work
and dedication to this pilot study.
Mr Peters contributed much information on the
natural history of wire grass while this project was in its formative stages.
He also
assisted during the first visits to the dry prairie near Shirttail Branch, designed the
monitoring strategy for wire grass survival and carried out most of the leg work for
the actual monitoring.
Also, many thanks to the 28 park staff and volunteers who, during
the transplant phase of the project, gave up their Saturdays to dig, plant and learn
how to distinguish between Aristida beyrichiana and Sporobolus junceus.
assistance this project would not have been feasible.
Without their
14
Literature Cited
Clewell, A.F. 1989. "Natural History of Wiregrass (Aristida Stricta
Gramineae). "Natural Areas Journal 9(40, pp. 223-233.
Michx.,
Florida Natural Areas Inventory; Florida Department of Natural Resources. 1990.
Guide to the Natural Communities of Florida. Tallahassee, Florida. 111 pp.
Florida Park Service, District 4 Administration. 1994. "Vegetative Characteristics
of contiguous Dry Prairie on Two Soil Types in Hardee County, Florida (X-1-D).
Unpubl. 32 pp.
Hyde, A.G., et al. 1991. Soil Survey of Sarasota County, Florida. Soil Conservation
Service, U.S. Department of Agriculture.
Robbins, J.M., et al. 1980. Soil Survey of Hardee County, Florida.
Soil
Conservation
Service, U.S.
Department of
Agriculture.