Effectiveness of microtopographic structure in species recovery in degraded salt marshes

Highlights: • Seed retention restricts the recovery on bare patches rather than dispersal. • Microtopographic structures can facilitate seedling establishment via trapping seeds. • The facilitation by microtopographic structure is sustainable in the following years. • Larger and deeper microtopographic structures are more effective in the long term. - Abstract: Topographic heterogeneity is an important determinant of the distribution of resources and species and of species assembly. For example, the lack of microtopography in degraded salt marshes might restrict processes involved in the recovery of such ecosystems, such as seed retention. Therefore, we conducted a restoration study in degraded middle to high salt marshes, where self-recovery might be restricted by poor seed retention. We investigated the impact of microtopographic structures on seed retention and the re-establishment of pioneer vegetation patches. Our results showed that hollowed microtopographic structures are effective tools for allowing the re-establishment of pioneer vegetation patches by acting as seed traps and sustaining the recovery process that follows. Larger, deeper microtopographic structures entrapped more seeds and formed larger patches over the long term compared with smaller structures, highlighting the value of such structures to the successful recovery of degraded salt marshes.