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Tropical Succession

Started by jmkassak, March 02, 2011, 05:18:35 PM

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jmkassak

Hi Jonathan,

As you know, I'm modeling a tropical site, and I'm trying to understand the conversions that are occurring with inundation and erosion.  I attempted to go through the technical documentation to "Map out" the successive conversions that happen (e.g., using the table on p. 32 and information within the habitat category descriptions). However, I still have some holes.  Most critically, I'm trying to understand what habitat type converts to Regularly flooded marsh in a tropical system.  My understanding what that the "default" for a tropical system would be a conversion to mangrove when a fresh or dry habitat goes below the salt elevation.  Could this just be my irregularly flooded marshes converting to regularly flooded?  Is it the case in a tropical system that irregularly flooded marshes are never "created" (because the default is mangrove) and that regularly flooded marshes are only created as a result of inundation of existing irregularly flooded marshes?

I don't suppose anyone has attempted to draw out a "decision tree" with the conversions that you could share?

Thanks! 

Jonathan S. Clough

Hi Jennifer. 

For SLAMM 3, there was a very historical decision tree that I personally found completely indecipherable (it didn't fit on one page and there were various jumps and indecipherable abbreviations) so I abandoned that approach in favor of the bulleted-item list you see in the technical documentation.  The latter approach is not as intuitive, but hopefully more completely transparent.  Perhaps at some point we could find some software that would help us to make a complex decision tree image that is clear. 

With regards to your question, irregularly flooded marsh convert to mangrove in a tropical (i.e. mangrove dominated) system when they fall below their lower elevation boundary.

No habitat should convert to regularly-flooded marsh in a tropical system because mangrove is assumed to dominate the intertidal zone.

-- Jonathan

jmkassak

Hi Jonathan,

Thanks for this description, I now see what happened.  It looks like not all of our subsites met the "Tropical" threshold, despite the fact that they are all part of the same system.  Do you think it would be appropriate, than, in explaining this situation, to essentially add the regularly flooded salt marsh in 2100 to the mangrove acreage, stating that all of those reg. flooded marshes should have converted to mangrove?  Do the implications of this issue extend beyond this simple explanation?

Thanks,
Jen

Jonathan S. Clough

That is probably fine to do and the answer will probably be pretty-much the same.  For the record, the implications of the site being considered "tropical" (mangrove dominated) are as follows:

1. Inundated dryland becomes mangrove rather than beach or transitional salt marsh.
2. Inundated irregularly-flooded marshes and transitional salt marshes become mangrove rather than regularly-flooded marshes.
3. Saline inundated inland fresh marsh, tidal fresh marsh, tidal swamp, and cypress swamp also assumed to become mangrove.

The tropical designation is set as a function of initial-condition mangrove at a site.

-- Jonathan

jmkassak

Thank you Jonathan, this is very helpful.  One final question: in a tropical system, is the parameter "Regularly Flooded Marsh Accretion Rate" then applied to Mangroves?  It is not clear from the documentation.

Jonathan S. Clough

Mangroves are assumed to accrete at their own rate, currently hard-wired into the model at 7.0 mm/year.  However, this will inflexibility will shortly change (in the next beta version of the model forthcoming).

jmkassak

Excellent, thanks Jonathan!

jmkassak

Well, I thought that was my last question on this topic, but I've discovered another.  What, if anything, is converting to Transitional Salt Marsh in a tropical system?  I'm assuming that there is still some conversion to this category based upon my results.  In sites that I know were recognized as tropical I still see some transitional marsh popping up.  But in sites that were not recognized as tropical, significantly more is created.  As a follow-up similar to my previous question, can we assume roughly that most of these transitional marshes in 2100 really ought to be mangroves?

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