Our coastal forests were minimally impacted after the first 10 hours of saltwater exposure in June 2022 and grew normally for the remainder of the year. We increased the exposure to 20 hours in June 2023 and the forest remains largely undisturbed, although tulip poplar are absorbing water from the soil more slowly, which can be an early warning signal.
Everything changed after 30 hours of exposure in June 2024. Tulip poplar leaves in the forest began turning brown in mid-August, several weeks earlier than usual. By mid-September, the forest canopy is bare, as if winter has come. These changes did not occur in nearby land, which we treated in the same way, but occurred with freshwater rather than seawater.
The early resilience of our forests can be partly explained by the relatively low salt content of the water in this estuary, where water from freshwater rivers and seawater mix. Rain that fell after the 2022 and 2023 experiments washed the salt from the soil.
But a major drought occurred after the 2024 experiment, so salt was still present in the soil then. Plants exposed longer to saline soils after our 2024 experiment may have exceeded their ability to tolerate these conditions.
The seawater poured into the fires in Southern California is salty, highly concentrated seawater. And the conditions are there was very dryespecially compared to our East Coast woodlot.
Visible changes in the ground
Our research team is still trying to understand all the factors that limit a forest's ability to tolerate saltwater and how our results apply to other ecosystems like those in the Los Angeles region. Angeles.
Leaves turning from green to brown before fall is a surprise, but there are other surprises hidden in the soil beneath our feet.
Rainwater seeping through the soil is usually clear, but about a month after the first and only 10-hour exposure to salt water in 2022, the soil water turned brown and stayed that way for two years. The brown color comes from carbon-based compounds leached from dead plants. It is a process similar to making tea.
