Any part of conifer trees (pine, cedar, juniper etc) produce oils that have vapor that is toxic on some levels. The most popular use is of course aromatic cedars used in closets and hope chests to kill of keep bugs out.
Most mulches I see come through our shop are conifer trees. So, like Don says NO.
Aspen is a different family of trees all together. Also aspen chips are not a by product of mass lumber production. Aspen is considered a weed tree. It was over planted by a lumber company, in the 60's, after they raped the land of pines. Then out government in their wisdom gave them a grant on find a way to use it!. Hence the creating of particle board and wafer board and all its newer uses. Yes our government gave millions to a company to do research so they could make more money. But is tht surpizing?
Aspen is inert as far as oil vapor and toxins. Bark is very thin so no real mulch of bark is made.
Just a big of aspen history. It is usually grossly over priced for reptile use.
Conifers Bad.
Aspen Good.
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Thanks for reading.
Big Tom
www.herpzilla.com