The role of coastal ecotones: a case study of the salt marsh/upland transition zone in California

1 Ecotones, the transition zones between adjacent ecological systems, may intensify or concentrate the flow and processing of materials and organisms between systems. 2 To determine whether the salt marsh/upland transition zone is an ecotone, both in functioning as a habitat, as well as concentrating materials and organisms, I conducted an extensive survey of 12 marsh/upland transition zones in the Pt Reyes area of California. 3 The high saltmarsh was identified as an ecotone, with biological and physical conditions distinct from the adjacent marsh plain and upland. It supports a unique plant assemblage and greater total soil nitrogen than the adjacent upland. 4 Taxonomic richness patterns did not reflect changes in habitat spatial characteristics (e.g. ecotone area, ecotone area/perimeter), instead showing a quadratic correlation along the gradient, with increased diversity of both plants and spiders in the ecotone. Spider richness was enhanced with increased vegetation complexity, which was greatest in the ecotone. 5 This study presents empirical evidence that suggests coastal marsh/upland ecotones harbour increased diversity and may concentrate nitrogen pools, thereby highlighting the need for further research investigating the relationship between landscape connections and the coupling of species and biogeochemical processes.