Transcript Slide 1

Dynamics of Nutrient Runoff Following Wetland Restoration Along the Illinois River
Clint Martin, Ashlyn Borges, and Sherri Morris
Background
Bradley University, Peoria, IL
Objective
Land-Use Change
The objective of this study was to follow changes in ecosystem dynamics as restoration progresses at Wightman Lake by
• Over 95% of the original wetland in Illinois, Indiana, and Iowa has been lost; most of this land has been contained
monitoring N and P flow across the site, soil C, and soil nutrient turnover (N and P) pre and post restoration.
behind levee systems, drained, and converted to farmland (Zedler, 2003).
• Extensive tiling, tillage, and fertilization has increased the flow of sediments and nutrients into aquatic ecosystems
from these lands (Hey, 2002).
Importance/Functionality of Wetlands
• Ecosystem services provided by wetlands include water retention, nutrient sink capacity, and biodiversity support
(ESA, 2000).
• The availability of these ecosystem services depends entirely on proper ecosystem function (long water retention
time, sheet flow of water, appropriate vegetation, etc.) (Jordan et al., 2003).
• The increased runoff due to modern agricultural practices (tillage, fertilization, etc.) has increased the importance of
these ecosystem services; excessive additions of nutrients and sediments causes extensive detrimental effects on
both freshwater and coastal aquatic ecosystems. Soil uptake and storage can decrease these impacts.
Wetland Restoration
• A growing percentage of land worldwide is undergoing wetland restoration.
• One such project has been initiated by Ducks Unlimited at Wightman Lake, a 370 acre parcel near Sparland,
Illinois; the restoration is part of a larger program to restore/protect a 15-mile stretch of the Illinois River directly north
Water
of Peoria, Illinois.
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bottomland forest, replanted agricultural land).
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Time (days)
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Figure 2. Carbon evolution (µg CO2-C/g soil/day) for agriculture and forest soils to 10 cm at
Wightman Lake. Incubation data will ultimately be used to evaluate soil C pool sizes
• All data were analyzed using ANOVA (Proc. Mixed; SAS 1999).
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• Outflow to the Illinois River from the wetland is currently higher than input to the system.
• There are significant differences in the rate of C evolution between the agricultural soils and forest soils (Figure 2).
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• There is significantly greater soil C and N in the forest soils compared to the agricultural soils (Figure 3).
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• The soils did not differ in C:N ratio.
• Thirty day nitrogen incubations had significantly greater immobilization in the agricultural soils compared to the
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forest soils (data not shown).
mgN/ha
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Sampling Location Distance from
Wetland (mi)
Sampling Location Distance from
Wetland (mi)
Figure 5. Mean orthophosphate concentration in
mg P/L for six sampling locations across three
time points. Each histogram bar represents the
mean ± standard error. Histogram bars labeled
with the same lower-case letter were not
significantly different at P < 0.05. *An asterisk
represents a point where no sample was taken
due to low water levels.
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Discussion
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mgC/ha/mgN/ha
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Figure 4. Mean nitrate-nitrogen concentration
in mg NO32--N/L for six sampling locations
across three time points. Each histogram bar
represents the mean ± standard error.
Histogram bars labeled with the same lowercase letter were not significantly different at P
< 0.05. *An asterisk represents a point where
no sample was taken due to low water levels.
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Soils
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• The pattern detected was less consistent than that for nitrate.
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• There were significant differences in stream orthophosphate at most sample locations across the season (Figure 5).
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Phosphorus
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Nitrate and orthophosphate movement in the Illinois River play a significant role in the degrading quality of downstream aquatic
ecosystems. Restoration of wetland nutrient dynamics at Wightman lake should decrease nutrient flow to the Illinois River. We will
follow changed in ecosystem function as the restoration project is completed and plant establishment becomes permanent.
Monitoring will allow us to evaluate the degree to which the restoration project meets stated goals. Restoring functioning wetlands
along the Illinois River will improve river quality and protect downstream communities. More studies are needed that follow
changes in ecosystem dynamics following restoration to evaluate the degree to which different restoration plans achieve desired
goals.
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Water
• Nitrate patterns in this system are likely related to patters of N fertilizer use for agriculture; the Wightman Lake wetland
restoration should serve to reduce movement of nitrate into the Illinois River.
• Contributions of orthophosphate from this system to the Illinois River do not appear to be exceedingly high but appear to be
consistent with current regional trends.
• More research is necessary to understand patterns and the role that wetland restoration will play in managing movement of
orthophosphate into the Illinois River.
Soils
• Agricultural soils have a wide C:N ratio with high rates of N immobilization; these soils have great potential to hold the nitrogen
that is added as it settles out of diverted agricultural run off.
• The added N and likely P will increase soil and plant productivity across the restored Wightman Lake property; this should result
in increased soil C sequestration.
Conclusions
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Ecological Society of America (ESA). (2000). Nutrient pollution of coastal rivers, bays, and seas. Issues in Ecology, 7.
Hey, D.L. (2002). Nitrogen farming: harvesting a different crop. Restoration Ecology, 10(1):1-10.
Jordan, T.E., Whigham, D.F., Hofmockel, K.H., Pittek, M.A. (2003) Nutrient and sediment removal by a restored wetland receiving agricultural runoff. J.
Environ. Qual., 32:1534-1537.
SAS Institute Inc. (1999). SAS OnlineDoc®, Version 8, Cary, NC: SAS Institute Inc.
Zedler, J.B. (2003). Wetlands at your service: reducing impacts of agriculture at the watershed scale. Front. Ecol. Environ., 1(2):65-72
.
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Orthophosphate (mg P/L)
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0.05
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mgC/ha
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• Wetland nitrate output was lower than concentrations in Gimlet Creek.
References
05/30/07
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• Stream nitrate concentration differed across the season (Figure 4).
• Nitrate was greatest on the slope and decreased as Gimlet Creek approached the wetland.
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In
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• Ammonium content of Gimlet Creek was very low across the dates measured.
• Water from late season dates (May 30, June 20) had significantly greater nitrate than early dates.
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Nitrogen
significantly.
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Nitrate (mg NO3 -N/L)
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Water
• Water from early season dates (April 9, 23, 30) had relatively low nitrate concentrations and did not differ
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Results
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Analysis
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• Soil analysis included C and N mineralization, C/N ratio, and resistant C/N ratio.
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Forest 0-10cm
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• Selection of sampling locations attempts to accurately represent different functional areas at the site (wetland,
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prior to restoration.
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• Soil cores were taken from 22 locations across the project area at 3 depths (0-10 cm, 10-25 cm, and 25-50 cm)
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Soils
mg CO2-C/g soil/day
• N and P content were determined with LACHAT Autoanalyzer using standard procedures.
Ag 0-10cm
Nitrate (mg NO3 -N/L)
Water
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04/09/07
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Methods
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Soils
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Figure 1. Map and restoration plans for Wightman Lake (provided courtesy of Ducks Unlimited).
through the monitoring of ecosystem dynamics.
Orthophosphate (mg P/L)
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• Evaluating the degree to which ecosystem services are restored requires assessment of ecosystem function
• Samples were filtered to remove suspended sediments and frozen for analysis.
Nitrate (mg NO3 -N/L)
a demonstration site for conservation practices.
over 5 time points from April to June 2007.
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farmland with trees (Figure 1). Project goals include increasing bird habitat, improving water quality, and establishing
Phosphorus
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• Restoration plans include enhancing wetland habitat, improving the bottomland forest stand, and replanting former
• Samples were collected from 6 locations (in the Gimlet Creek watershed and at wetland inflow/outflow locations)
Nitrogen
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Orthophosphate (mg P/L)
• The wetland system is fed by the Gimlet Creek watershed, which primarily drains farmland.
Acknowledgements
Ag
Forest
Figure 3. Mg C/ha, Mg N/ha and C:N ratio to a depth of 50 cm corrected for equivalent soil
weight in forest and agricultural soils at Wightman lake.
This research was supported by the National Great Rivers Research and Education Center (NGRREC).
Thanks to Ducks Unlimited, particularly Eric Schenck, for maps, guidance, and an informative tour of
Wightman Lake. Thanks also to students in McConnaughay and Morris labs for their help in collecting and
processing samples.