Tree Fight!
First, lets be clear, you said oldest living organism, not specifically tree (which would still be incorrect)
The first link: All it says is that the trees are over 2,000 years old. Not 12,000. All the info I can find only indicates 2,000 years old, about half of the record. The site you link also only calls it "one of the oldest". Not "THE" oldest.
The second link: All it says is that the tree is the Oldest Living Tasmanian tree.
The third link: You got that email form this site:
http://www.nyu.edu/projects/julian/treetalk.html
The thing is, that very site as a link debunking the "12,000" year old tree idea:
http://www.nyu.edu/projects/julian/oldestliving.html
So the tree ISN'T the oldest or even close to being 12,000 years old. What is old, is it's root system, which works by "cloning".
So the single oldest organism, minus those that "clone" to stay alive, is the "Methuselah" at 4,767 years a bristlecone pine.
but if you want to include cloning than your tree is FAR from the oldest thing, which you touched on, and I touched on in my 3rd link of my original post:
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Not sure why you posted the 4th link, as that is a different plant (shrub, actaully) entirely from the one you called the oldest (remember you said "The oldest living organism", not tree or plant) and is what I origianlly assumed you accidently meant, but it isn't really the oldest.
Even your link calls it just "the Oldest Plant Clone in the World"
I actually already posted about this in my third link tho, that link incidently also meantions the huon pine as at least 2,000 years old, but ranks it below the 4,767 year old bristlecone pine.
Tho all this might be for nothing as crustose rock lichens may in fact be many thousands of years old. Without "cloning"