Factors Affecting Germination of a Dominant Salt Marsh Species are Context-Dependent: Implications for Coastal Seed-Based Restoration

Abstract

Restoration of coastal salt marshes is often limited by their capability to revegetate, either through natural recruitment or active planting methods. Despite the critical need for efficient revegetation methods, direct seeding remains an underrepresented approach in coastal wetland restoration. Additionally, tidal inundation poses special challenges for coastal Seed-Based Restoration (SBR) relative to terrestrial habitats, with tides displacing seeds from the marsh platform. To determine factors potentially influencing successful establishment in coastal wetlands, we conducted a series of greenhouse and lab experiments with Salicornia pacifica (pickleweed), the dominant plant in California marshes. We determined pickleweed seed viability using standardized germination tests. Additionally, we tested factors that influence pickleweed seed viability and germination rates, such as soil moisture, soil type, and sowing depth. We found that pickleweed seeds had an average viability of 22.5%, which increased with larger-sized seeds. We also determined that the most effective dormancy-breaking pretreatments varied by soil type: a one-day cold stratification in freshwater maximized germination in benign soils, whereas a seven-day cold stratification in saltwater maximized germination in stressful soils. Finally, we determined that the optimal conditions for sowing seeds are surface sowing under moderate moisture. Creating conditions to maximize viability and germination is crucial to ensure the greatest chance of successful revegetation post restoration. Our study, which sequentially tested factors affecting different phases of the early life history of a dominant foundation species, can inform SBR for other coastal plants. This approach can help coastal land managers successfully implement SBR for habitat restoration.