Sand movement and vegetation in the Apostle Islands, Lake Superior
Recent sand movement was inferred from grain morphology, modal grain size, and grain size distributional skewness of samples from the surfaces of beach–dune landscapes. Negative skewness indicated recent net deflation, and either positive skewness or small modal grain size indicated recent net aeolian accretion. Large grains that were shiny and angular indicated surfaces that could not have been deposited by wind. Net deflation occurred where vegetational cover was below 10%, in foredunes and an interdunal blowout. All other sites in dunal, interdunal, or forested zones showed evidence of net accretion or a balance of accretion and deflation. Net accretion was evident in locations with as little as 15% cover. Relationships between sand movement and vegetational composition could not be separated from relationships with total cover. The sandy foreland of one island was bulldozed during the 1950s. This apparently brought coarser Holocene beach deposits near the surface, which limited the severity of blowout by providing a deflation armor. Ammophila breviligulata has not recolonized the interdunal zone of this island, though it persists in this zone on the other islands. The study of grains in cores may reveal the history of vegetational cover at a site.