Roots.

From prop roots to pneumatophores, the most conspicuous part of a mangrove is definitely its incredible aboveground root system. These roots don't just look amazing though -- they actually serve numerous functions for the tree. Mangroves are usually found in soils that are either permanently or frequently inundated by water and thus have little or no oxygen. Aboveground roots collect and diffuse oxygen to belowground root structures, as all parts of the plant - roots included - must have oxygen to function.

 

Mangroves live in the coastal zone and face continuous, moderate to low energy wave impacts. They must remain anchored in soft sediments even through this constant motion and in the face of storms and storm surge. The root systems allows the tree to withstand these forces and prevents erosion of the soil surface.

Mangrove aboveground roots are able to slow down the tidal velocity causing suspended sediments to drop out of the water column in and around the roots. Most sediments in this zone are not resuspended as waves and tides flow back out of the forest and sediments are left behind. It is incredible to see the impacts of even a single mangrove tree on an eroding shoreline.

 

For my project, I'll be not only counting aboveground roots, but sampling and measuring belowground root biomass too. I'm wondering if substantially/repeatedly trimming the canopy of a mangrove tree reduces the ability of the root system to continue to function as described above.

In Florida, law generally permits people to trim a tree to six feet tall without any need for permits. But why six feet? Does trimming to six feet change the structure or coverage of the root network above or belowground?

To find out how belowground roots are affected, I'll need to collect high quality, consistent, deep root samples. Enter, the $1,000 peat corer :)

I'll be using a Russian peat borer, because of its ability to collect samples even in waterlogged conditions. The Russian borer has a tube with a sharpened edge which is rotated and cuts through the soil and roots. A plate on one side of the borer stabilizes the body of the borer so that it doesn't rotate as the tube is rotated. The tube is turned until a complete sample is collected and it is closed against the plate, preventing the soil and roots in the sample from being disturbed (or lost in the case of waterlogged soils) during extraction.

I'm super excited to start collecting and measuring roots. I'll be using a software such as SmartRoot: http://www.uclouvain.be/en-smartroot or WinRhizo: http://regent.qc.ca/assets/winrhizo_about.html to fully analyze the root samples that I collect. I'm hoping to categorize roots by size class using the software, by live to dead root ratio, and by biomass at different soil depths and distances from a given tree.

And, on a completely unrelated note - things that make me happy:

Baby mangroves!

 

Signs of how resilient the mangrove really is...