Punctuated decadal morphodynamics and coupled vegetation succession along a nontidal, wave-dominated Great Lakes barrier spit, Gull Point, Lake Erie, U.S.A.

Abstract

The Presque Isle Peninsula is a compound barrier-spit system perched atop a recessional moraine along Lake Erie’s southeastern coast. Its distal terminus, Gull Point, has grown to an extent of around 0.6 km2 since the early 1900s, promoted by beach nourishment along the peninsula proper and later influenced by a change in local hydrodynamic regime following breakwater installation near the attachment point. This coastal setting has set the stage for an analysis of ridge landform- and vegetation-succession dynamics using historical aerial images, a series of high-resolution LiDAR datasets, transect/quadrat surveys of vegetation, and increment core dates of tree cohorts on dune ridges separated by swales and lagoons. The general evolutionary model is one of punctuated landform growth to the east by lateral accretion, interspersed with erosional events and ridge recurving towards the backbarrier. Eastern cottonwood (Populus deltoides), with its minimally provisioned wind- and water-dispersed seeds, colonizes the margins of newly deposited sand ridges as discrete cohorts, and dominates the tree stratum of Gull Point. These cohorts are increasingly mature moving from distal to proximal zones, and consistently reflect the temporal sequence of ridge morphology. Vegetation communities, representing a primary successional chronosequence, are delineated into four phases extending back to the 1950s, which are roughly demarcated by erosional ridgelines of topographic prominence, revealing a tight coupling of lake-level trends, geomorphology, and vegetation dynamics. This provides coastal researchers with a means of understanding landform-age relationships across structurally complex strand areas for which age-relationships cannot be ascertained by aerial photographic records alone.