I hope you've read Vinge's _A_Deepness_In_The_Sky_? :)
I wonder if anyone has written an essay of the significance of wood as a medium of value in science fiction. I first noticed it with the burl in Niven's the _Integral_Trees_, but it also shows up in Cherryh and lots of other authors.
Another example: in Richard K. Morgan's Altered Carbon, "mirrorwood" from Harlan's World is prized on Earth, but used as a common building materia on its homeworld.