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Three Years after Construction, Alternative Planting
and Management Strategies in Experimental Marshes Induce
Differences in Biodiversity and Heterogeneity, but not in Function
Jake J. Grossman & John E. Petersen,
Oberlin College Environmental Studies & Biology
[email protected]
Background and Objectives
3. Spatial Analysis: In ’04-’07 photographs were taken weekly during the
growing season at the corner of each cell from atop a 3 m ladder. In ’06
and ’07, aerial photographs were taken using a camera suspended from a
kite.
Two key goals for wetland restoration in agricultural landscapes are to create
biodiverse habitat and to cultivate desirable ecological functions such as nutrient
retention. Wetland restoration practices vary considerably with respect to plant
species management. The goal of our ongoing research is to assess the effects of
management practices on ecosystem structure and function.
2. Water Quality:
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No clear differences among treatment are evident in any measures of water
quality. Dissolved inorganic phosphorus concentrations have remained low
throughout (<0.04 mg/L). Ammonium is rarely detectable.
Mean nitrate + nitrite among cells '05 to ’07
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NO2,3 (mg/L)
Experimental System & Management
In the summer of ’03 we constructed and planted six hydrologically isolated ¼ ha
wetland “cells” on marginal farmland in NE Ohio owned by Oberlin College.
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2005 2006 2007
Early spring
Cells were assigned to one of three treatment groups based on plant species
management. “High-intensity” cells (2&5) and “low-intensity” cells (3&6) were seeded
with 12 native species and planted with propagules of 11 species. The high intensity
cells received multiple re-plantings of propagules in subsequent years. “Selfdesigning” cells (1&4) were not planted or seeded. Cattails (Typha angustifolia and
latifolia) and reed canary grass (Phalaris arundinacea) were controlled in all cells.
Geo-referenced aerial photographs of a self-designing treatment (left) and a
high-intensity treatment (middle) taken in August of ’06. The photograph of the
high intensity treatment has been converted (right) to species polygons (green
= Nymphaea odorata, blue = Sparganium americanum, purple = Juncus
effusus, yellow = Echinochloa crus-galli, blue = Sagittaria latifolia, orange =
other wetland species, black = open water).
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Average nitrate concentrations are consistently low (<0.2 mg/L), but exhibit a
regular seasonal decrease from spring to late summer. (Error bars in graph
above are standard deviations in concentration calculated among all six cells).
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Thus far, environmental factors common to all of the cells appear to be a
stronger determinant of biogeochemical dynamics than management
practices.
3. Spatial Analysis:
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Preliminary Findings
Species richness
1. Biodiversity:
Methods
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2. Water Quality Monitoring: During the growing season weekly measures
have been made of turbidity, dissolved oxygen, dissolved inorganic nitrogen
and dissolved inorganic phosphorus.
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Literature Cited:
Peet RK, TR Wentworth, and PS White. 1998. A flexible, multipurpose method for recording
vegetation composition and structure. Castanea 63: 262-274.
Smith JL. 2006. The first two years of macrophyte community establishment in six created
freshwater marshes undergoing invasive species management. Master’s Thesis, Ohio State
University.
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Native species
Non-native
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High-intensity
Low-intensity
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An initial investment of approximately 10 person-hours/cell (40 hrs/ha) in
seeding and planting during the first two years was sufficient to initiate
development of a robust plant community with significantly higher species
diversity and greater spatial heterogeneity than is present in unplanted cells.
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No clear difference is evident in the invasibility of planted and unplanted
treatments. Management effort necessary to control invasive cattails and
reed canary grass declined rapidly from over 6 hrs/cell in 2004 to less than 1
hr/cell in 2007.
Self-designing
Native species richness, Shannon-Weiner diversity, and FQAI diversity are
significantly higher in planted than in unplanted cells but do not differ
among high and low intensity treatments. Non-native plant richness, like
native plant richness, is higher in planted wetlands. (Error bars on graph
above are ranges between duplicates in each treatment group).
Planted species, including arrow head (Sagittaria latifolia), water lily
(Nymphaea odorata), and bur reed (Sparganium americanum) are major
components of the plant communities in planted cells, but not of those in
the unplanted cells. We speculate that in spite of their proximity, planted
and unplanted cells will remain biologically distinct for decades to come.
Spatial heterogeneity appears to be much higher in planted than in unplanted
cells. We are in the process of determining the most effective means of
quantifying the spatial dynamics of plant community development using a
combination of aerial photography, GPS, and GIS analysis.
4. Management:
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1. Biodiversity Surveys: Species diversity and richness and percent cover in
each cell have been determined annually using methods adapted from the
Ohio EPA (Peet et al., 1998; Smith 2006).
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2005 2006 2007
Late summer
Next steps
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Our immediate priority is to develop techniques for quantifying spatial
patterns in plant community dynamics during ecosystem development.
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In future years we plan to explore the effect of species diversity on
function by simulating agricultural runoff with fertilizer and nutrient
additions.