Seedling Emergence from Seed Banks in Ludwigia hexapetala-Invaded Wetlands: Implications for Restoration.

Brenda J Grewell,Morgane B Gillard,Caryn J Futrell,Jesús M Castillo

doi:10.3390/plants8110451

Brenda J Grewell, Morgane B Gillard + Show 2 more

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https://doi.org/10.3390/plants8110451

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Abstract

Soil seed banks play a critical role in the maintenance of wetland plant communities and contribute to revegetation following disturbances. Analysis of the seed bank can therefore inform restoration planning and management. Emergence from seed banks may vary in response to hydrologic conditions and sediment disturbances. To assess the community-level impact of exotic Ludwigia hexapetala on soil seed banks, we compared differences in species composition of standing vegetation among invaded and non-invaded wetlands and the degree of similarity between vegetation and soil seed banks in northern California. To determine potential seed bank recruitment of L. hexapetala and associated plant species, we conducted a seedling emergence assay in response to inundation regime (drawdown vs. flooded) and sediment depth (surface vs. buried). Plant species richness, evenness, and Shannon’s H’ diversity were substantially lower in standing vegetation at L. hexapetala invaded sites as compared to non-invaded sites. Over 12 months, 69 plant taxa germinated from the seed banks, including L. hexapetala and several other exotic taxa. Seedling density varied among sites, being the highest (10,500 seedlings m−2) in surface sediments from non-invaded sites subjected to drawdown treatments. These results signal the need for invasive plant management strategies to deplete undesirable seed banks for restoration success.

Highlights

Exotic plant invasions are a major threat to native ecological communities and can significantly reduce native species diversity [1]
While the potential role of seed banks in both secondary invasions and restoration has long been recognized [5,6], very few scientific studies or restoration projects have evaluated the relationships between weed invasions and soil seed banks, despite their important role in vegetation dynamics [7]
The presence of the invader L. hexapetala was associated with pronounced decreases in plant species richness, evenness, and diversity in the Laguna de Santa Rosa, though the magnitude of these effects varied by site (Figure 1)

Summary

Introduction

Exotic plant invasions are a major threat to native ecological communities and can significantly reduce native species diversity [1]. The management of invasive plants has become a conservation priority that is an essential component of wetland ecosystem restoration. While the potential role of seed banks in both secondary invasions and restoration has long been recognized [5,6], very few scientific studies or restoration projects have evaluated the relationships between weed invasions and soil seed banks, despite their important role in vegetation dynamics [7]. These ecological relationships are rarely considered in ecological restoration plans.

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