Date of Award
Doctor of Philosophy (PhD)
Brenda B. Casper
Coastal foredunes are among the most geologically unstable and dynamic terrestrial habitats, shaped by wind and waves and vegetation acting as ecosystem engineers in a biogeomorphic coupling that has only recently begun to be appreciated. Storm disturbances can de-vegetate and erode microcosms, creating barren blowout depressions. Between storms, plants will colonize or recolonize blowouts and the back shore. However, the mechanism and biotic and abiotic controls on re-establishment, and thus recovery, are unknown, as are the biogeomorphic implications of what species establishes itself, although all of these factors will impact future storm response. We explore biotic, arbuscular mycorrhizal fungi (AMF), and abiotic (substrate flux) controls on post-storm recolonization and the potential role of clonal integration in this by native Ammophila breviligulata and invasive Carex kobomugi. To reveal underlying biogeomorphic relationships driving topographic heterogeneity, we test how plant density, configuration, and morphology, impact initial dune genesis in nebkha formation. AMF likely play a minimal role, in recolonization as viable AMF are largely lacking and randomly distributed in barren soils. Conversely, both A. breviligulata and C. kobomugi, support persistent viable AMF in the soil and had colonized roots, despite documented differences in AMF dependencies. AMF presence may not be necessary for colonization because clonal integration can facilitate blowout establishment, but if the distal plant is severed from the rhizome, then AMF-associations can shift in response. Colonization occurs primarily from lateral spread of existing vegetation between growing seasons where areas with more stable substrate may have increased rates of recolonization. However, erosion can also stimulate recolonization. With regards to the role of plants as ecosystem engineers, plant morphology, density, and configuration impact topography, most notably, with larger plants supporting larger nebkha and nebkha shape and height varying by species both in field and lab-setting. As such, although C. kobomugi does not appear to alter belowground AMF communities, it may alter the morphological trajectory of an evolving foredune, impacting future storm response. Coastal instability will only increase with the effects of climate change. Understanding the biological processes underpinning recolonization and thereby recovery post-disturbance will only grow increasingly important in a changing world.
Charbonneau, Bianca Reo, "From The Sand They Rise: Post-Storm Foredune Plant Recolonization And Its Biogeomorphic Implications" (2019). Publicly Accessible Penn Dissertations. 3651.