I am working on a coastal salt marsh ecosystem, and need an organism which has a large trunk. From my poking around it seems to me a large woody grass, or a Prototaxites like fungus\lichen might best suit my needs, but I am not sure.
This organism needs to:
Grow quickly, hopefully reach mature size after 2 - 6 months (anywhere in that range is fine).
Have a trunk with a diameter at the ground of 0.5 - 1.5 meters at maturity (anywhere in that range is fine).
Have some kind of root-like system, but it doesn't need to run deep, only a meter or so, though deeper than that is also acceptable.
And of coarse survive well in the aforementioned salt marsh conditions.
Would an organism fulfilling these criteria be possible? I briefly considered something akin to a mangrove tree, however they lack the central trunk I'm looking for.
Any suggestions as for existing organisms, or designs for fictional ones, are welcome.
I would like to give a preemptive thank-you to anyone who takes the time out of their day to answer this question.