system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars/Mandalorian] Where did the Tusken Raiders get the wood to create the scorpions they used to fire bolts at the Krayt Dragon?

Exactly where are the trees on Tatooine?
gpt
While Tatooine does not have the traditional kind of forest trees you'd think of, it does have a biosphere that includes plant life.  Japor ivory wood being one example that would be suitable for construction, but other types of wood are available as well.

Beyond that, Tusken Raiders aren't completely non-technological, and they do trade as well.  The ballistae need not be constructed entirely of native wood.