Grantee Research Project Results
2000 Progress Report: Applying Ecological Succession Theory to Evaluate Wetland Restoration in Urbanizing Coastal Watersheds
EPA Grant Number: R826111Title: Applying Ecological Succession Theory to Evaluate Wetland Restoration in Urbanizing Coastal Watersheds
Investigators: Craft, C. B. , Stevenson, R. Jan , Megonigal, J. P. , Broome, S. W.
Institution: Indiana University - Bloomington
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 1998 through May 31, 2001 (Extended to May 30, 2002)
Project Period Covered by this Report: June 1, 1999 through May 31, 2000
Project Amount: $534,239
RFA: Ecosystem Restoration (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management , Aquatic Ecosystems
Objective:
The objective is to assess the degree of full or complete restoration of wetland structure and function on restored salt marshes and other ecologically similar restored wetlands.Progress Summary:
Field work is completed and effort is focused on completing laboratory analyses and graduate student research. Two Ph.D. students and one M.S. student are completing their research projects and will graduate within the next year. Taxonomic and trophic identification of benthic invertebrates from the North Carolina sites is nearly completed and identification of Virginia samples will begin soon. We also completed data collection from two additional sites, above and beyond those described in our original plan to work. One study evaluates the use of soil-based metrics as indicators of recovery in a restored salt marsh in Georgia (Craft, 2001b). The second study describes plant community and soil development over a fifteen-year period following brackish-water marsh construction (Craft, et al., in review).
Several manuscripts from the research project have been published or are "in press" (see Publications). Findings from Craft (2001a) are presented below that describe a functional and structural trajectory (FAST) model of wetland ecosystem development following salt marsh construction.
Primary Productivity
Comparison of above- and below-ground biomass revealed that constructed marshes did not achieve functional equivalence to natural marshes for more than a decade following establishment (Figures 1a and b). Aboveground biomass was significantly lower in constructed marshes of 11 years old or less, as compared to the corresponding reference marshes. Likewise, the 1, 2 and 11 year-old constructed marshes contained significantly less belowground biomass (0-30 cm) than the reference marshes. In constructed marshes older than 10 to 12 years, the trajectories for above- and below-ground biomass exceeded biomass levels found in reference marshes (Figures 1a and b). Increased Spartina biomass production (relative to reference marshes) in older constructed marshes has been observed in other studies. Craft, et al. (1999), reported higher levels of above- and below-ground biomass in two constructed salt
Figure 1. End-of-season (a) above- and (b) below-ground biomass and (c) stem height and (d) density along a chronosequence of constructed salt marshes and paired reference marshes. The area between the dashed lines represents the 75 percent to 125 percent range of equivalence. Numbers within the graphs are the constructed marsh values.
marshes during the first 3-10 years following marsh establishment. Higher
biomass stocks in these constructed marshes may reflect an "adolescent" growth
spurt in these youthful ecosystems.
Habitat Complexity
Spartina structural attributes such as stem height and density also required 10 to 12 years to achieve equivalence to natural marshes. Young (<12 year-old) constructed marshes typically had higher stem densities but stems that were not as tall as Spartina stems of natural marshes (Figures 2c and d). Zedler and Callaway (1999) also observed that, for at least 10 to 12 years following establishment, a constructed S. foliosa marsh in southern California had shorter stems than a comparable natural marsh. In spite of higher stem density, young constructed marshes had less aboveground biomass. Canopy architecture of Spartina has been shown to be important for nesting of an endangered bird species (light-footed clapper rail), as nests in taller stems are less likely to be inundated (Zedler, 1993). Likewise, Spartina stem density may enhance finfish and invertebrate utilization of constructed and natural marshes by providing refuge from predators (Minello and Zimmerman, 1983).
Biogeochemical Cycling
Soil Development. Soil organic C and N pools were very slow to develop. Even after 30 years, constructed marshes contained less organic C and N (0-30 cm) than the reference marshes (Figures 2a and b). After 28 years, soil N pools approached 200 g m-2, which was substantially less than the 300-500 g m-2 found in natural marshes. Similar to N, after 28 years, organic C pools in the constructed marshes (2.5-3 kg m-2) was much lower as compared to reference marshes (5-10 kg m-2). Likewise, other studies of constructed salt marshes report that, even after 10 to 25 years, constructed marshes contain less soil organic C and N than their reference counterparts (Craft et al. 1988, 1999, Zedler and Callaway 1999). Surprisingly, the youngest constructed marshes, 1 to 2 years in age, contained substantial pools of N (50-60 g m-2). It is likely that sparse canopy cover of Spartina in the young marshes allows more light to reach the soil surface, resulting in increased N inputs from epiphytic and soil N fixing blue-green algae.
Figure 2. Soil (a) organic C and (b) N pools (g m-2, 0-30 cm) along a chronosequence of constructed salt marshes and paired reference marshes. The area between the dashed lines represents the 75 percent to 125 percent range of equivalence. Numbers within the graphs are the constructed marsh values.
Methanogenesis. Comparison of methane emissions in constructed and natural marsh soils revealed that, regardless of age, constructed marshes had consistently higher methane production. Methane emissions were measured using 13-day anaerobic incubations of soils (n=5 per marsh) collected from eight constructed/natural marsh pairs. Salinity of the incubation water was 20 o/oo. If methane production from each constructed marsh was equal to its corresponding natural marsh, a plot of the constructed (created)-natural pairs would fall on a 1:1 line (Figure 3). However, relatively more methane was emitted from constructed marsh soils regardless of age. We conclude that labile carbon compounds constitute a larger portion of the soil carbon pool in constructed marshes than natural marshes.
This conclusion is supported by data comparing organic matter quality of macro-organic matter of constructed and natural marshes (data not shown). Macro-organic matter in constructed marshes, especially young (<10 year-old) ones, contains mostly labile organic compounds like carbohydrates and water soluble compounds and relatively little lignin (15-20 percent). In natural marshes, organic matter contains proportionally more lignin (>30 percent) that is recalcitrant and not readily decomposable.
Figure 3. Methane emissions from constructed (created) versus natural marsh soils. Note that all constructed marshes lie above the 1:1 line, indicating consistently higher methane production from constructed marsh soils.
Future Activities:
In addition to manuscripts published or in press, additional manuscripts are being prepared and will be submitted soon to peer-reviewed journals. Jan Stevenson (Michigan State University) and graduate student will submit a manuscript to Wetlands comparing algae productivity and species composition along a chronosequence of constructed salt marshes and natural "reference" marshes. Steve Broome (NC State University) and graduate student are working on a manuscript describing plant community and soil development of constructed salt marshes. This manuscript likely will be submitted to Soil Science Society of America Journal or Limnology and Oceanography. Pat Megonigal (Smithsonian Environ. Research Center) and graduate student will submit a manuscript comparing decomposition and trace gas fluxes in constructed and natural salt marshes. Chris Craft (Indiana University) and graduate student are preparing a manuscript describing the development of benthic invertebrate communities following marsh construction. Chris Craft and colleagues also plan to submit a manuscript to BioScience that summarizes the key findings of the project, including trajectories describing the rate of development of various ecological attributes over time following salt marsh construction. This manuscript will be submitted during summer of 2001.References:
Craft CB, Broome SW, Seneca ED. Nitrogen, phosphorus and organic carbon pools in natural and transplanted marsh soils. Estuaries 1988;11:272-280.
Craft CB, Reader JM, Sacco JN, Broome SW. Twenty-five years of ecosystem development of constructed Spartina alterniflora (Loisel) marshes. Ecological Applications 1999;9:1405-1419.
Zedler JB. Canopy architecture of natural and planted cordgrass marshes: selecting habitat evaluation criteria. Ecological Applications 1993;3:123-138.
Zedler JB, Callaway JC. Tracking wetland restoration: do mitigation sites follow desired trajectories? Restoration Ecology 1999;7:69-73.
Minello TJ, Zimmerman RJ. Fish predation on juvenile brown shrimp, Penaeus azetecus Ives: the effects of simulated Spartina structure on predation rates. Journal of Experimental Marine Biology and Ecology 1983;72:211-231.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 9 publications | 6 publications in selected types | All 5 journal articles |
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Craft CB. Co-development of wetlands soils and benthic invertebrate communities following salt marsh creation. Wetlands Ecology and Management 2000;8(2-3):197-207. |
R826111 (2000) |
Exit |
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Craft CB. Soil organic carbon, nitrogen, and phosphorus as indicators of recovery in restored Spartina marshes. Ecological Restoration 2001;19(2):87-91. |
R826111 (2000) |
Exit |
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Craft C, Broome S, Campbell C. Fifteen years of vegetation and soil development after brackish-water marsh creation. Restoration Ecology 2002;10(2):248-258. |
R826111 (2000) |
Exit |
Supplemental Keywords:
estuary, sustainable development, public policy, decision making, monitoring., RFA, Scientific Discipline, Water, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Water & Watershed, Restoration, State, Southeast, Mid-Atlantic, Ecological Risk Assessment, Aquatic Ecosystem Restoration, Watersheds, wetlands, ecological succession theory, biodiversity, watershed, Virginia (VA), tourism, regional economies, sustainable development, decision making, coastal environments, conservation, ecological recovery, marshes, aquatic ecosystems, urbanizing coastal watershed, North Carolina (NC), water quality, watershed restorationRelevant Websites:
http://www.indiana.edu/~speaweb/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.