so another thread of research.  lots of great info out there.  at some point i'd love to have searchable databases of n-fixers and fast carbon pathway support species as a resource to the permaculture community.  for now I offer these links and lists and thoughts.

From Koreen Brennan

Just found this resource for nitro fixing fodder legumes, wonderful! http://www.fao.org/ag/AGP/AGPC/doc/Publicat/Gutt-shel/x5556e00.htm#Contents

in response:

If I were to put in sub-tropical to tropical long term canopy tree legumes, these would be at the top of my list:

carob, tamarind, ice cream bean, tipuana tipu.  

mainly because I like to eat the first three and would like to get experience with the fourth after hearing about it.

I'm surprised it gets so cold in Florida, what is your location?  my understanding was that zone 9 was down to 20 F?  microclimate possibilities?  perhaps you can get some good varieties from NAFEX http://www.nafex.org/ or the rare fruit tree associations. http://www.crfg.org/ florida rare fruit http://www.rarefruit.org/

I love the work Julia Morton did in Fruits of the Warm Climates.  I'm guessing there is lots more out there now, but haven't been researching tropics in a while.

Carob, Ceratonia siliqua: http://www.hort.purdue.edu/newcrop/morton/carob.html

tamarind, tamarindus indica http://www.hort.purdue.edu/newcrop/morton/tamarind.html

Ice Cream Bean, Inga edulis http://www.hort.purdue.edu/newcrop/duke_energy/inga_edulis.html

Tipuana tipu http://www.public.asu.edu/~camartin/plants/Plant%20html%20files/tipuanatipu.html

Another FAO doc. http://www.fao.org/docrep/003/T0632E/T0632E02.htm

Suggests: prosopis sp as well.

Black Locust??? native to Southeast N. America.

casaurina pines? http://en.wikipedia.org/wiki/Casuarina  Awesome non-rotting building material too.

more for understory? baptisia, lespedeza, ceanothus, tephrosia, senna, desmodium, perennial peanut, crotolaria, guessing there's many more

I have used most of the species noted in the FAO doc you shared and liked them in Hawai'i.  never had an issue with spreading.  if you like, cut them before seed formation.  these are common n-fixers for tropical and sub-tropical use: 

Gliricidia sp., Leucaena sp., Calliandra sp., Albizia sp., Acacia sp., Erythrina sp., Cassia sp., Parkinsonia sp., Inga sp., Sesbania sp., Crotalaria sp., ...

I have used cassia trees not sure on the species, birds absolutely loved them so even without N-fixing nodules, the import to the system was substantial.

other links to check out with some species listshttp://science.jrank.org/pages/3895/Legumes-Native-legumes-North-America.html

http://www.winrock.org/fnrm/factnet/factpub/factsh.htm

I've some palownia planted in zone 5-6. no experience with zone 4.  there i would definitely use Robinia, Elaeagnus, Gleditsia, and consider Sophora, alnus, gymnocladus, maackia, and cladrastis  as overstory, many mid- understory, shepherdia, caragana, elaeagnus, baptisia, Hippophae, cercis, alnus, maybe amorpha canescens, all dependent on water availability and soil type etc....I might even go with rhamnus although I know people are sensitive about buckthorn in the midwest.

Perhaps a useful source is oikos tree crops http://www.oikostreecrops.com/store/home.asp and

lawyer seed and plant nursery http://www.lawyernursery.com/  worth getting the seed list/catalog many more species than bare roots

I forgot about this one which is also a list topper with many functions

Moringa oleifera and other Moringa sp.  not legumes but fast carbon pathways and high nutrition valuehttp://www.hort.purdue.edu/newcrop/duke_energy/Moringa_oleifera.html

http://moringafarms.com/

http://www.mobot.org/gradstudents/olson/moringahome.html

http://en.wikipedia.org/wiki/Moringa_oleifera

http://www.winrock.org/fnrm/factnet/factpub/FACTSH/moringa.htm

http://agroforestry.net/scps/Moringa_specialty_crop.pdfhttp://www.worldagroforestrycentre.org/sea/products/afdbases/af/asp/SpeciesInfo.asp?SpID=1169

a permaculture article on ecologcal applications of moringa and mulberry with sites in florida mentionedhttp://www.perennialsolutions.org/cuba-mass-planting-moringa-and-mulberry

From Robyn Francis:

I live in humid subtropics and have some winter frosts.

The legumes I've had greatest success with are:

Perennial pigeon pea (Cajanus cajan) great shrub legume, can plant quite closely, terrific chop-and-drop spp to build up mulch, and nurse plant for establishing other trees. Is affected by severe frost, however if densely planted they send out new shoots from lower stem and branches in spring. Nodulate prolifically so good N-fixers. Only live 3-4 years.

Trees:
Tipuanu tipu - grows well but can grow quite large - I have these as an emergent canopy over my subtropical food forest. See a rare volunteer seedling popping up here and there, but are not invasive - or maybe the wallabies keep them in check.

Albizzia julibrissin are great smaller tree legume and very frost hardy (seen them growing in Europe) and have had no evidence of self seeding or invasive potential here.

Cow pea as a summer annual legume are quite prolific.

 I don't recommend using dolichos or desmodium app (too invasive), also honey locust is a shocking weed in our climate here where folk have grown it - spreads prolifically especially along water courses as an impenetrable vicious thorny thicket. I've also eliminated Inga edulis as a tree legume in my system, it self seeds prolifically and the birds and fruit bats spread seed into nearby rainforest areas.

Have you looked into Tagasaste (Chamaecytisus palmensis) ? It doesn't like our heavy clay but grows well in more sandy soils in subtropics and temperate areas.

from me:

a switch back to temperate climate resources
http://tcpermaculture.blogspot.com/2011/05/plants-nitrogen-fixers.html

http://www.tcpermaculture.blogspot.com/2012/09/pioneer-species-for-temperate-climate.html

http://tcpermaculture.com/plants.html

What is definitely lacking on this list are non-N-fixing fast carbon pathways.  lots out there, often called weeds which need re-assessment regarding utility and ecosystemic management.

feedback, comments, improvements, and additions welcome.