Biotic and abiotic predictors of ecosystem engineering traits of the dune building grass, Ammophila breviligulata

Abstract

Ecosystem engineers are species that fundamentally influence their community and ecosystem by creating or altering the physical structure of habitats. However, the function of ecosystem engineers is variable and can depend on abiotic and biotic factors. In this study, we characterized the ecosystem engineering traits of plant size and tiller density for the dune grass, Ammophila breviligulata, in 37 sites across a broad geographic gradient in the western Great Lakes region. We also measured 20 biotic and abiotic factors related to climate, soil chemistry, and fungal symbionts associated with these survey sites and assessed their relationships with A. breviligulata population traits and dune plant species richness. Climate factors, especially temperature and precipitation, were positively associated with A. breviligulata tiller size, while soil organic matter was the only factor associated with tiller density. Several factors, including temperature, soil nitrogen, and mycorrhizal colonization, were associated with plant richness across our sites. Our results suggest that climate can influence at least some ecosystem engineering traits (i.e., plant size) of an important dune building species, although general conclusions from our work indicate that the population trait tied most closely with dune building ability—population density—is not strongly influenced by climate at the regional scale. This offers insight for conservationists interested in preserving intact dune ecosystems in a changing climate, but further work is needed to reconcile conflicting lab and field studies.