PS 43-181 - Above- and belowground functional traits in a key coastal grass species are differently driven by stress and disturbance

Abstract: Environmental stress and disturbance are two key factors shaping plant life history strategies and patterns of biodiversity. These factors are particularly important in coastal sand dune habitats: winds and storm activity regularly bury dune plants in sand, while concurrently soil nutrients and water are extremely limiting. However human-driven nutrient enrichment and climate change may alter the relative importance of these factors on sand dunes, which may have cascading effects on not just plant community composition but also ecosystem functioning. In 2022, we established monitoring plots in four sand dune sites along the western Michigan coast to examine the relative impacts of climatic and nutrient stress compared to burial disturbance on vegetation. These sites spanned an increasing gradient of climatic and nutrient stress but decreasing gradient of sand movement disturbance from south to north. We hypothesized that increasing climatic and nutrient stress would override the importance of disturbance and would decrease aboveground biomass of Ammophila breviligulata—a key dune-building species—while increasing belowground allocation. From each site, we collected fifteen A. breviligulata tillers and measured biomass, root and leaf traits, and mycorrhizal colonization. Above- and belowground components responded differently to the stress and disturbance gradients, with aboveground biomass negatively associated with disturbance, while belowground traits—including total belowground biomass, root biomass, and root length—negatively associated with stress. Contrary to our hypothesis, these results suggest that above- and belowground growth in A. breviligulata may be driven differentially by stress and disturbance which may not align with generalized hypotheses of plant responses to global change. Furthermore, alterations in these traits may impact coastal dune development and stability, with implications for long-term response to global change.