This dataset accompanies the manuscript: 'Sediment availability provokes a shift from Brownian to Lévy-like clonal expansion in a dune building grass.' Reijers et al., accepted at Ecology Letters Abstract 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 organizations. 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 optimization 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 optimize their engineering ability depending on their physical landscape. Methods Data stored in this repository are collected during both a field survey and a one-year mesocosm experiment in which we measured traits from marram grass (Ammophila arenaria) growing in conditions with either low or high sediment availability or deposition. Focus was primarily on spatial shoot organization and the step size distribution of the distances between shoots as a proxy for clonal expansion strategy. These shoot coordinates were extracted from still images (photos from the field survey are included in the repository, images from the mesocosm experiment are available upon request) and distances were calculated using a nearest neighbour connecting algorithm. Detailed description of these methods can be found in the accompanying publication (Reijers et al. Ecology Letters) or in a previously published method protocol (Reijers & Hoeks, 2019 Protocol Exchange). In addition we measured several plant growth related parameters such as: shoot length, shoot diameter, rhizome depth and leaf C:N ratio for the plant sampled during the field survey and shoot height, shoot numbers, shoot growth and leaf C:N ratio for the plants growing in the mesocosm experiment. Next to plant related data we measured several environmental characteristcs in the field including grain size, elevation, plant available nitrogen, organic matter, distance to sea and sediment deposition. For the mesocosm experiment we measured soil height, volume, organic matter, C:N and moisture content. A readme file was included to further explain file content.

This study was financially supported by the Netherlands Organization of Scientific Research (NWO Building with Nature grant 850.13.052 and NWO-Vidi grant 16588)