Sediment availability provokes a shift from Brownian to Lévy‐like clonal expansion in a dune building grass

In biogeomorphic landscapes, plant traits can steer landscape development through plant‐mediated feedback interactions. Interspecific differences in clonal expansion strategy can therefore lead to the emergence of different landscape organisations. Yet, whether landscape‐forming plants adopt different clonal expansion strategies depending on their physical environment remains to be tested. Here, we use a field survey and a complementary mesocosm approach to investigate whether sediment deposition affects the clonal expansion strategy employed by dune‐building marram grass individuals. Our results reveal a consistent shift in expansion pattern from more clumped, Brownian‐like, movement in sediment‐poor conditions, to patchier, Lévy‐like, movement under high sediment supply rates. Additional model simulations illustrate that the sediment‐dependent shift in movement strategies induces a shift in optimisation of the cost–benefit relation between landscape engineering (i.e. dune formation) and expansion. Plasticity in expansion strategy may therefore allow landscape‐forming plants to optimise their engineering ability depending on their physical landscape.