Abstract
An ongoing debate in ecology is the relationship between community or ecosystem structure and function. This relationship is particularly important in restored ecosystems because it is often assumed that restoring ecosystem structure will restore ecosystem functioning, but this assumption is frequently not tested. In this study, we used a novel application of structural equation modelling (SEM) to examine the relationship between ecosystem structure and function. To exemplify how to apply SEM to explore this relationship, we used a case study examining soil controls on denitrification potential (DNP) in two restored wetlands. Our objectives were to examine (1) whether both restored wetland soil ecosystems had similar relationships among soils variables (i.e. similar soil ecosystem structure) and (2) whether the soil variables driving denitrification potential (DNP) were similar at both sites (i.e. the soil ecosystems were functioning in a similar manner). Using the unique ability of SEM to test model structure, we proposed a SEM to represent the soil ecosystem and tested this structure with field data. We determined that the same model structure was supported by data from both systems suggesting that the two restored wetland systems had similar soil ecosystem structure. To test whether both ecosystems were functioning in a similar way, we examined the parameters of each model. We determined that the drivers of DNP function were not the same at both sites. Higher soil organic matter was the most important predictor of higher DNP at both sites. However, the other significant relationships among soils variables were different at each system indicating that the soils were not functioning in exactly the same way at each site. Overall, these results suggest that the restoration of ecosystem structure may not necessarily ensure the restoration of ecosystem functioning. In this study we capitalize on an inherent feature of SEM, the ability to test model structure, to test a fundamental ecological question. This novel approach is widely applicable to other systems and improves our understanding of the general relationship between ecosystem structure and function.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 761-768 |
| Number of pages | 8 |
| Journal | Ecological Modelling |
| Volume | 221 |
| Issue number | 5 |
| DOIs | |
| State | Published - Mar 10 2010 |
| Externally published | Yes |
Bibliographical note
Funding Information:We are grateful to Dr. Jim Grace for helpful suggestions about the SEM analysis and Jen Morse for suggestions about the construct model. We thank Nicolette Cagle and Dean Urban for useful comments on an earlier version of the manuscript as well as several anonymous reviewers. We are also grateful to the following for help in the field and lab: Joseph Lozier, Tracy Hamm, Amanda Ward, Sarah Eminhizer, Erin Brosnan, Josie Bamford, Serwaah Agyapong, Aileen Malloy, Tisha Johnson, Jim Pahl, Wes Willis, Mengchi Ho, Paul Heine, Julie DeMeester, Mike Osland, Amani McHugh, Wyatt Hartman, Brian Roberts, Sharon Madden, and Stephanie Chin. This project was funded by grants from the City of Charlotte and Mecklenburg County, the Duke Wetland Case Studies Endowment, a Society of Wetland Scientist Student Research Grant, a Doctoral Dissertation Improvement Grant from NSF DEB-05-08763, as well as an NSF Graduate Research Fellowship to A.E. Sutton-Grier. A.E. Sutton-Grier was also partially supported by a Smithsonian Fellowship at the Smithsonian Environmental Research Center. M.A. Kenney was partially supported by the STC program of the National Science Foundation via the National Center for Earth-surface Dynamics under the agreement Number EAR-0120914.
Keywords
- Denitrification potential (DNP)
- Ecosystem function
- Ecosystem structure
- Structural equation modelling (SEM)
- Wetland restoration
