Group Title: Research brief - Soil and Water Science Dept. University of Florida ; SWS-01-1
Title: Soil phosphorus enrichment in the Everglades water conservation Area-2A
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Title: Soil phosphorus enrichment in the Everglades water conservation Area-2A
Series Title: Research brief - Soil and Water Science Dept. University of Florida ; SWS-01-1
Physical Description: Book
Creator: DeBusk, W. F.
Newman, S.
Reddy, K. R.
Publisher: Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville, Fla.
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Bibliographic ID: UF00072014
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

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SWS-01-1


r Soil and Water Science
i Research Brief

Unvrst of Flrd Intiut of Foo and. Agiulua S cie


SOIL PHOSPHORUS ENRICHMENT IN THE

EVERGLADES WATER CONSERVATION AREA-2A

W. F. DeBusk, S. Newman, and K. R. Reddy


The Everglades, a mosaic of sawgrass
marsh, sloughs and tree islands, once
encompassed the vast expanse of south
Florida from Lake Okeechobee to Florida
Bay. Essentially all of the modem-day
Everglades is contained within Everglades
National Park and the Water Conservation
Areas (WCAs). The WCAs were created
some 40 to 50 years ago, primarily for the
purposes of water storage, flood control and
recreation. Since their creation, the WCAs
have experienced sustained inputs of
nutrient-laden drainage water from the
Everglades Agricultural Area, and
consequently have shown strong evidence of
ecological
change.
Among the
more
noticeable
ecological
changes in
WCA-2A have
been the
transformation
w2A of native
sawgrass
(Cladium
jamaicense
_Crantz) marsh
and openwater
sloughs to dense stands of cattail (Typha
domingensis Pers. and T. latifolia L.) and
replacement of endemic periphyton
communities by algal species typically
associated with more eutrophic waters Soil


P concentration in WCA-2A has been
strongly linked to productivity, community
structure of
macrophytes,
periphyton,
and nutrient
cycling.
Increased
biological
production,
stimulated by loading of P from external
sources, has resulted in accelerated rates of
peat accretion, and P storage in impacted
areas near surface water inflows.
The overall objective of our study was to
evaluate recent (1990 to 1998) changes in
the spatial extent and patterns of soil P
enrichment (total P concentration) in
Everglades WCA-2A. The study was
accomplished by conducting a
comprehensive sampling and analysis of
surface soil across WCA-2A. Comparison
of results of the initial and follow-up studies
formed the basis of our analysis of recent
spatio-temporal patterns of soil P
enrichment.
Surface soil
(peat) and
overlying
flocculent
material was
sampled to a
depth of 10 cm
at 62 sites
within WCA-2A during October 1990 and
1998, for analysis of total phosphorus (TP)









content. Geostatistical methods were used to
create an interpolated grid of soil TP values
across WCA-2A.


Approximately 73% (31, 777 ha) of the
total land area of WCA-2A was considered
P-enriched (soil total P > 500 mg kg ') in
1998, compared with 48% of the land area
(20 829 ha) in 1990, an average increase of
1327 ha y-. Our results indicate that a soil P
enrichment "front" has maintained its
southerly progression into the relatively
unimpacted interior sawgrass marsh of
WCA-2A during the past several years.
Several decades of loading of nutrient-laden
agricultural drainage is reflected in the now
widespread P enrichment of surface soils in
WCA-2A. Historical and current spatial
pattems of soil P enrichment indicate that
the main source of P loading has been the S-
10 surface inflow structures along the
northeastern boundary of the study area. A
secondary source ofP loading and
subsequent soil P enrichment has been the
area downstream of the S-7 pump station, at
the western comer of WCA-2A.
Areal expansion of P-enriched soils in
WCA-2A may be viewed as a P front
advancing southward from the S-10 inflows
across the unimpacted interior sawgrass
marsh and slough region. Given that the P
enrichment gradient is relatively broad,
however, the front is actually quite diffuse
and therefore difficult to map as such. If the
P enrichment front is defined by the extent
of the proposed soil P concentration that
facilitates cattail invasion (650 mg kg1') its
location has progressed from about 5.5 km
south of S-10C in 1990 to 9.1 km in 1998.


The movement is equivalent to an average
rate of 436 m yr-' into the interior marsh of
WCA-2A. Using a similar approach we
estimate that the 1000 mg P kg-1 front has
advanced from 4.2 to 6.0 km to the south of
S-10C during the same period, equivalent to
a rate of 218 m yr-.
Soil P enrichment above historical
background concentrations can be
considered an indicator of ecological impact,
or change. Dynamic patterns of soil P
enrichment have been closely aligned with
documented changes in vegetation patterns,
most notably the change from native
sawgrass marsh to cattail marsh. Results of
this soil characterization study, showing a
substantial increase in the extent of
moderate soil P-enrichment, is indicative of
the magnitude of recent increases in the
ecologically-impacted area of WCA-2A.

Full text of this paper can be found at:
DeBusk, W.F., S. Newman, and K.R.
Reddy. 2001. Spatio-temporal patterns of
soil phosphorus enrichment in Everglades
WCA-2A. Journal of Environmental
Quality (in press).

AUTHORS

W.F. DeBusk,
Soil and Water Science Dept.,
P. O. Box 110510, University of Florida,
Gainesville, FL 32611 wfd(Amail.ifas.ufl.edu

S. Newman,
South Florida Water Management District
3301 Gun Club Road
West Palm Beach, FL 33416
Snewman@sfwmd. gov

K.R. Reddy,
Soil and Water Science Dept.,
P. O. Box 110510, University of Florida
Gainesville, FL 32611 krr(iTufl.edu

This research was supported by the Florida
Agricultural Experiment Station and a grant
from the South Florida Water Management
District and approved for publication as
Journal Series No. R-07647.




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