Rising plant demand strengthens nitrogen limitation in tidal marsh.

Area of Science:

• Ecology
• Biogeochemistry
• Environmental Science

Background:

• Nitrogen (N) is a critical nutrient for plant growth, but its limitation in ecosystems is debated due to increasing global N sources and sinks.
• Temperate marshes receive substantial human-derived N inputs, yet rising atmospheric carbon dioxide (CO2) may increase ecosystem N demand.

Purpose of the Study:

• To assess the severity and causes of nitrogen limitation in a temperate marsh ecosystem over 14 years.
• To investigate the influence of nitrogen addition, elevated CO2, sea level, and salinity on plant growth and N limitation.

Main Methods:

• Utilized a 14-year experiment with nitrogen addition and elevated CO2.
• Analyzed interannual variability in external drivers, plant growth, and porewater biogeochemistry.
• Assessed plant functional group responses to environmental changes.

Main Results:

• Found significant interannual variability in porewater nitrogen, plant growth, and experimental nitrogen effects.
• Sea level and salinity strongly influenced plant growth and nitrogen limitation.
• Elevated CO2 and increased flooding intensified nitrogen limitation for sedges.

Conclusions:

• Abiotic factors like sea level and salinity control plant growth, which in turn dictates nitrogen limitation.
• In this open-system marsh, increased plant nitrogen demand, driven by factors like elevated CO2, has outpaced nitrogen supply.
• Nitrogen limitation is a key factor influencing overall ecosystem productivity in temperate marshes.