Changes in coastal wetlands could alter carbon sequestration capacity

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Coastal wetlands are one of the most unique and important parts of the Connecticut landscape. They play an important ecological and economic role. A barrier against storms and floods, natural water filtration, an important support for fishing and one of the biggest carbon sinks on the planet – these are all essential functions of coastal wetlands.

Carbon sinks are reservoirs, natural or otherwise, that accumulate and store carbon. As climate change is largely fueled by carbon emissions from human activity, protecting coastal wetlands is quickly becoming a global priority.

Grasses in coastal marshes are particularly good carbon sinks because they can trap sediment very efficiently, and organic matter decomposes very slowly in anoxic sediments in wetlands. Coastal wetlands have 100 times more carbon accumulation rates than terrestrial forests.

Beth Lawrence, assistant professor of natural resources and the environment at the College of Agriculture, Health, and Natural Resources, received a Research Excellence Program (REP) grant to study how raising standards of the sea and coastal development can alter the stability of stored carbon. With her doctoral student, Madeleine Meadows-McDonnell, she is implementing a manipulation experiment to understand the role of plants in regulating soil carbon in coastal wetlands.

The REP Vice President Research Office provides seed funding to fuel innovative research, scholarships and creative projects.

These changes in coastal wetlands are altering the types of plants that can live in these marshes, which could affect their ability to sequester and store carbon.

In areas affected by sea level rise, plants that resist frequent flooding, such as native plants Alterniflora spartine grass, are more and more widespread. On the other hand, development along the coast intersects wetlands from the ocean with physical barriers such as roads or bridges. In these areas, invasive grass species such as Phragmites australis displace native species.

Plants play a direct role in carbon capture by influencing the activity of microbes in the soil and the levels of soil oxygenation. Lawrence’s lab recently discovered that organic matter breaks down faster Phragmites that native Spartina soil, suggesting that plants modify the environmental conditions that determine the efficiency of carbon storage differently.

One potential explanation for this difference is that plants release sugars from their roots (ie, “root exudates”) which stimulate the microbes responsible for decomposition. More active microbes use soil organic matter faster, so it’s a less efficient carbon store. Plants in wetlands also release oxygen from their roots, which can also promote microbial activity.

Lawrence hypothesizes that adding high quality soil carbon, such as type Phragmites produce, and oxygen will increase the rate of mineralization or decomposition of organic material.

“While increased release of sugars and oxygen from plant roots can stimulate microbial degradation of soil organic matter and promote the release of carbon dioxide in the short term, byproducts of microbial metabolism can help. to trap soil carbon which will be preserved in the longer term. , said Laurent.

Lawrence will use a new method to measure microbial activity in these wetlands – sugar. Cane sugar and beet sugar have different isotopic signatures; Lawrence and Meadows-McDonnell experimentally add sugars to mimic root exudation and will measure carbon isotopes in the gas released by microbes. This method is an inexpensive, non-toxic way to track carbon in microbial metabolites. They will also measure organic matter mineralization and aggregate stability, measures of the ability of marshes to capture and store carbon.

This research will determine how different plants affect the length of organic matter persistence in coastal wetland soil.

This knowledge will help scientists better manage this essential natural resource by understanding how common plant species found along the northeast coast of the United States alter the stability of soil carbon.

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