Can you have more than one skin?

[aaminoff]

Barkskin, Stoneskin, Ironskin. If you have one of those effects, and then get a second one, does the new one overwrite the old? Both in terms of the amount of protection you get (10,15, or 20, respectively), and in terms of the vulnerabilities you get (fire, cold, lightning)?

Strength of Gaia says that gives Barkskin. If they do overwrite, then presumably SoGaia would overwrite Stone or Ironskin. If you cast them in the other order, Stoneskin overwrite the Barkskin part of SoG? But hopefully not the other parts of SoG (natural regen, +1 nature)