Seedling emergence from seed banks in Ludwigia hexapetala invaded wetlands: Implications for restoration

Authors: Grewell, Brenda; GILLARD, MORGANE - University Of California, Davis; Futrell, Caryn; CASTILLO, JESUS - University Of Seville

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2019
Publication Date: 10/25/2019
Citation: Grewell, B.J., Gillard, M., Futrell, C.J., Castillo, J.M. 2019. Seedling emergence from seed banks in Ludwigia hexapetala invaded wetlands: Implications for restoration. Plants. 8(11):451. https://doi.org/10.3390/plants8110451.
DOI: https://doi.org/10.3390/plants8110451

Interpretive Summary: Many plants have viable seeds present in the soil profile that are referred to as soil seed banks. Scientific knowledge of seed bank characteristics and environmental conditions that trigger germination and seedling emergence are important for conservation and restoration planning. 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. In the case of invasive plant species, knowledge of seed bank composition and environmental responses is particularly critical for risk assessments of secondary invasion from seed banks following disturbances such as weed management actions. 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 associate 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 seed banks including L. hexapetala and several other exotic taxa. Seedling density varied among sites, being highest (10,500 seedlings m-2) in surface sediments from non-invaded sites subjected to drawdown treatments. Results signal the need for long-term invasive plant management strategies to deplete undesirable seed banks for restoration success.

Technical 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 associate 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 seed banks including L. hexapetala and several other exotic taxa. Seedling density varied among sites, being highest (10,500 seedlings m-2) in surface sediments from non-invaded sites subjected to drawdown treatments. Results signal the need for invasive plant management strategies to deplete undesirable seed banks for restoration success.