A study published in September’s San Francisco Estuary and Watershed Science shed light on some essential questions about what triggers seed generation in wetland habitat. “Wetland restoration practices can be enhanced by a solid understanding of basic plant life history and species ecology,” says co-author Taylor Sloey of Yale-NUS College in Singapore. The researchers looked at three questions: what seeds are present in the seed bank (the viable seeds that accumulate naturally in the soil), and how exposure to cold and flood affects their germination. The study was based on seed bank samples taken from wetlands on the Delta’s Liberty Island. Though the island was drained and farmed throughout most of the 20th century, it has been naturally recolonized by both tides and wetland species since a levee failed in 1997. Today, the site is dominated by California bulrush, along with cattail and hardstem bulrush. However, when seed bank samples obtained from the site were germinated in a greenhouse setting, the most common species to sprout were cattail and tall sedge rather than bulrush. “I’m sure the seeds were present, they just didn’t germinate,” Sloey said. “So we followed up with a germination study.” This second part of the study explored whether restoration managers could help bulrush get established by exposing seeds to cold temperatures before they were sown. While cattail and California bulrush respectively showed no reaction (or a negative reaction) to increased time chilled at 5 °C, hardstem bulrush responded very favorably, only beginning to sprout after being chilled for at least two weeks. Longer cold times led to increased germination success, up to 16 weeks. Lastly, the study found that inundation in water of 10 centimeters or more for 100 days stopped all three species from germinating. “I think this research aids in filling in some knowledge gaps about important wetland plant species,” said Sloey. “We hope our findings help to inform future restoration practices.”

 

Pearls in the ocean of information that our reporters didn’t want you to miss
Photo: Jacoba Charles
 

While the acreage of wetland restoration projects is growing throughout the Delta, scientists are still working to understand how best to help these areas become fully functioning, complex habitat as quickly and successfully as possible.

A study published in September's San Francisco Estuary and Watershed Science shed light on some essential questions about what triggers seed generation in wetland habitat. “Wetland restoration practices can be enhanced by a solid understanding of basic plant life history and species ecology,” says co-author Taylor Sloey of Yale-NUS College in Singapore. The researchers looked at three questions: what seeds are present in the seed bank (the viable seeds that accumulate naturally in the soil), and how exposure to cold and flood affects their germination. The study was based on seed bank samples taken from wetlands on the Delta's Liberty Island. Though the island was drained and farmed throughout most of the 20th century, it has been naturally recolonized by both tides and wetland species since a levee failed in 1997. Today, the site is dominated by California bulrush, along with cattail and hardstem bulrush. However, when seed bank samples obtained from the site were germinated in a greenhouse setting, the most common species to sprout were cattail and tall sedge rather than bulrush. “I'm sure the seeds were present, they just didn't germinate,” Sloey said. “So we followed up with a germination study.” This second part of the study explored whether restoration managers could help bulrush get established by exposing seeds to cold temperatures before they were sown. While cattail and California bulrush respectively showed no reaction (or a negative reaction) to increased time chilled at 5 °C, hardstem bulrush responded very favorably, only beginning to sprout after being chilled for at least two weeks. Longer cold times led to increased germination success, up to 16 weeks. Lastly, the study found that inundation in water of 10 centimeters or more for 100 days stopped all three species from germinating. “I think this research aids in filling in some knowledge gaps about important wetland plant species,” said Sloey. “We hope our findings help to inform future restoration practices.”

 

About the author

Jacoba Charles is a naturalist and science writer. Her first article, at age eight, was about the behavior of ducks as observed from the roof of her family’s barn. It went unpublished. She later graduated from the Columbia School of Journalism (2007). In addition to writing for Estuary News, her work has appeared in The New York Times, Salon, and Modern Farmer, Bay Nature, Marin Magazine, and various literary publications. Her botany blog can be found at flowersofmarin.com and her website is jacobacharles.com. She lives in Petaluma with her family.

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