Differences in the morphology of restored and invaded foredunes on the north spit of Humboldt Bay, California, U.S.A.
Invasive plants have altered wide-ranging coastal dune vegetation communities worldwide, and the effects of nonnative vegetation and invasive plant management on dune geomorphology are of interest to many coastal land managers, researchers, and coastal communities. This study compared the slopes, elevations, and profiles of invaded and restored foredunes on the North Spit of Humboldt Bay, California, using data from a high-resolution 2010 digital elevation model. Restoration of foredunes by removing invasive European beachgrass (Ammophila arenaria [L.] Link) took place over the last three decades in approximately half of the study area, and the restored areas now primarily support American dunegrass (Elymus mollis Trin.) and other native dune species. Despite recently voiced public concerns that restoration might be permanently lowering the foredune, restored and invaded areas showed no significant difference in height. However, invaded foredunes were significantly steeper with a flatter, plateau-like top, while restored areas were more gently sloping with rounded peaks. Foredune heights increased from the southern end of the study area to the north, regardless of restoration status, suggesting that other factors control foredune height.