title: Hierarchical organization of a Sardinian sand dune plant community.
abstract: Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune.
authors.affiliation: Department of Science for Nature and Environmental Resources, University of Sassari , Sassari , Italy.
authors.forename: Valentina
authors.identifier: 0000-0002-0873-4979
authors.initials: V
authors.lastname: Cusseddu
authors.affiliation: Department of Science for Nature and Environmental Resources, University of Sassari , Sassari , Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Ceccherelli
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University , Providence, Rhode Island , United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Bertness
keywords: Community assembly; Community structure; Disturbance; Facilitation; Hierarchical organization; Plant competition; Shoreline ecology