Most decking is wood

Most decking is wood and most wood decking is treated pine. Treated pine is treated diy above ground round pool deckto prevent rot (CCA has been phased out and has been replaced now with ACQ & other treatments) These are acronyms for the chemicals in the treatments. The wood most commonly treated is southern pine. The nature of the wpc composite fencingwood itself, not the treatment, makes it prone to twisting and warping.
Cedar is second in popularity in most places and has been used in the vast artificial composite wood deckingmajority of our decks over the years. It resists rot and is considerably more stable than southern pine.