Ecosystem engineers can govern ecosystem dynamics, yet ecosystem consequences of trait variation within engineering species are often overlooked. Combining field and greenhouse experiments with mathematical modelling, this study aimed to assess the relative importance of heritable and non-heritable trait variation within the engineer species Spartina alterniflora in controlling salt marsh erosion. In the field experiment, plots along a devegetated shoreline were restored with wild and cultivated sources to test whether populations exerted different control on erosion. The greenhouse experiment investigated whether genotypic trait differences were conserved when genotypes were exposed to elevated nutrients. A modelling approach was used to extrapolate empirical findings to temporal and spatial scales involved in landform evolution, considering spatial patterns in trait variation. The field experiment revealed that erosion rates were higher in plots planted with a wild, non-local source population as compared to plots planted with cultivars or local genotypes. Differential erosion could not be explained by differences in biomass, suggesting that other traits and resource use are stronger determinants of erosion. In the greenhouse experiment, cultivars and wild genotypes exhibited trait-specific differences in phenotypic plasticity under changing nutrient availability. Nutrient regime and heritable trait differences explained 70% of observed variation in soil shear strength. Soil shear strength increased when plants received more nutrients, but plant genotype had an equal or larger influence on soil characteristics. Model simulations suggested that older marshes (with large clones) and genetically diverse marshes (with high spatial variance in soil shear strength) may experience higher mean erosion rates. However, simulations also showed that average erosion rates are easily underestimated if the observation period is short, as variability of annual erosion rates and the probability of mass failure events were also mediated by clone size and composition. These findings illustrate that heritable and non-heritable trait variation interact with environmental conditions and landform history, together driving geomorphological processes crucial to the persistence of coastal marshes. Consideration of these interacting factors is needed when deploying ecosystem engineers for habitat restoration. / 1 / Brittany Marie Bernik
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_46041 |
| Date | January 2015 |
| Contributors | Bernik, Brittany M. (author), Blum, Michael (Thesis advisor), School of Science & Engineering Ecology and Evolutionary Biology (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic |
| Rights | Embargo |
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