Growth response of dune‐building grasses to precipitation

The formation and development of coastal dunes are influenced by the growth of dune‐building grasses. Concurrently, the development of coastal dunes has been positively related to growing season precipitation, which might be due to precipitation promoting the growth of dune‐building grasses. However, a direct response relationship between precipitation and dune‐building grasses has yet to be identified. We explored the impact of precipitation on dune‐building grass species using a three‐step approach. (1) We assessed how plant‐available soil moisture changed with precipitation along an elevation profile from embryo dune to foredune. (2) We quantified the growth response of European marram grass (Ammophila arenaria [L.] Link) and sand couch (Elytrigia juncea [L.] Nevski) in a controlled pot experiment with water treatments derived from long‐term precipitation records. (3) We explored the impact of different precipitation scenarios on the growth of dune‐building grasses. Our field monitoring results showed that changes in soil moisture of the upper soil profile (0–50 cm) closely followed precipitation dynamics for all topographic positions. In our controlled pot experiment, soil moisture significantly increased plant growth in plant attributes associated with dune‐building, irrespective of species. Our scenario analyses indicated that prolonged periods with deviations from average growing season precipitation significantly affect plant growth, with extremely dry years reducing plant growth up to 23% and extremely wet years increasing plant growth up to 32%. Hence, in precipitation‐dependent coastal dune ecosystems, future extreme climatic events might have considerable consequences for dune development by notably influencing the growth of dune‐building vegetation.