The effect of seed mix additions on emergent community composition with implications for Iowa CREP wetland restorations

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Halpin, KristiLee
Major Professor
William Crumpton
Arnold van der Valk
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Ecology, Evolution, and Organismal Biology

With extensive wetland losses nationwide, people have turned to wetland restoration as a mechanism to return these valuable ecosystems to the landscape. However, the appropriate restoration method is not straightforward due to conflicting research documenting different outcomes from the same methodology used to re-vegetate the restoration. Some argue that active re-vegetation is not necessary as nearby sources will colonize naturally. Others state that active re-vegetation is necessary because not all species have the dispersal capabilities necessary to arrive at a restoration site.

This thesis explores whether a supplemental seed source and timing of seed application with respect to wetland construction will enhance emergent community composition in wetland restorations compared to sites not seeded. It also evaluates site and design attributes by examining the coverage and diversity of their vegetation. We found that the seed mix was capable of producing differences in community composition especially for the shallow water species mix, however, many sites were dominated by an invasive species, Phalaris arundinacea. Evaluation of the physical characteristics revealed that only relative cover of P. arundinacea and the remaining non-seeded species were significantly affecting total cover of seeded species. Furthermore, Simpson’s diversity was significantly impacted by whether the site was seeded and the age of the restoration. All remaining physical characteristics were not significant. Lastly, a negative correlation was found between species richness and absolute cover of non P. arundinacea species, and relative cover of P. arundinacea.

In sum, this thesis shows that adding a native seed mix to Iowa CREP wetland restorations is capable of improving species diversity specifically from the fringe species in the shallow water mix, however, there is still high variability with the outcome of species composition due to barriers of ecosystem development such as invasive species and high nutrient loads.

Fri Jan 01 00:00:00 UTC 2016