Optimizing salt marsh restoration with context-dependent emergent trait mimicry and donor material selection

Abstract

Ecosystem restoration is increasingly promoted as a tool to halt and reverse ongoing losses of coastal ecosystems and the services they provide. Recent work highlights that, in ecosystems shaped by habitat-forming species, restoration yields can be enhanced by temporarily mimicking key emergent traits. These traits are not expressed by individuals, but emerge when organisms aggregate to locally suppress environmental stress and are often vital for species' establishment and persistence. However, it remains unclear to what extent emergent-trait mimicry is context dependent and how donor material selection affects restoration success. Here, we experimentally studied the potential context dependency of trait mimicry and the effect of using donor source populations from contrasting environments in a three-year salt marsh restoration experiment. At two sites with contrasting hydrodynamic conditions – one relatively sheltered and the other exposed – we cross-transplanted plants from both sites into bare soil and 3D-printed biodegradable structures as trait-mimics, mimicking either sparse or dense vegetation patches. After three years, transplants from the sheltered site had two-fold higher survival and four-times more shoots compared to transplants from the exposed site. Furthermore, we found that in sheltered conditions, structures increased survival compared to control treatments, and plants in dense trait mimics grew the highest number of shoots. By contrast, most transplants in exposed conditions were lost after year one regardless of origin and treatment. We conclude that the donor source is a vital determinant for transplant establishment, and that emergent trait mimicry is context dependent for salt marshes, emphasizing the need for trait-mimics tailored to local conditions to increase restoration success.