Marshes and Mangroves Flashcards
Why are marshes and mangroves so important?
Both types of tidal wetland
They support a lot of high value ecosystem services
Huge amount of natural capital
Support a huge percentage of the world’s fisheries
Juvenile stages
They’re extremely rich sources of carbon rich soil
Carbon sinks
Why not drowned?
Ability to engineer their position relative to sea level.
Combination of sediment transport and vegetation that allows these tidal wetlands to keep pace with sea level changes.
If you have a tidal system, once or twice a day a prism of water brings minerals and sediment up dune through vegetation, which slows it down and deposits.
Once delivered on the rising tide it tends to stay
Sediment is also created through breaking down biomass (more sediment because more minerals = more growth)
How do salt marshes grow?
Above ground, mineral sediment settles out of the water column and onto coastal wetland soils during periods of tidal flooding
Plant shoots influence mineral sediment deposition by slowing water velocities, and add organic matter to the soil surface deposition rates highest in low-elevation marshes (inundated for long periods of time) lowest in high-elevation marshes (rarely flooded). More plants -> slower -> more deposition.
FEEDBACK: Supply of nutrients = plant growth…
Below ground, the balance of plant root growth and decay directly adds organic matter to the soil profile, raising elevation by sub-surface expansion
Faster rates of above-ground plant growth promote greater standing biomass ->
slows water velocities on the marsh platform
lowers wave height
reduces erosion
enhances mineral sediment deposition
Similar feedbacks between flooding, plant growth and sub-surface expansion operate in the root zone -> highly organic soils that persist for thousands of years
Suggests that…
more extensive flooding associated with sea-level rise should be accompanied by enhanced accretion.
The feedback, in words
Parts of the feedback sea-level rise rate sedimentation rate above-ground plant growth rate below-ground plant growth rate •AND: wetland geography (e.g., location, slope, neighboring land cover, etc)a
What marshes is deposition highest?
Low elevation- the deeper the tidal prism is above it the more sediment will be suspended.
What does sea level rise suggestively lead to?
Enhanced accretion
