where in the english speaking world are tree roots called 'tree moors'?

I can’t verify that “tree moors” is a standard English term for tree roots in any specific English-speaking region from the available evidence. In mainstream English, moor usually means a heath or open upland, not tree roots, and standard dictionaries do not list “tree moors” as a recognized term.

What it may be

It’s more likely one of these:

• A local dialect word.
• A misunderstanding of a similar-sounding phrase.
• A niche term from a specific online community rather than a broad regional usage.

Best-supported answer

Based on the evidence I found, I can’t place “tree moors” in the English- speaking world as a known, established name for tree roots.

Closest standard wording

If you meant the visible surface roots of a tree, common English terms are:

• exposed roots.
• surface roots.
• buttress roots, depending on the shape.

TL;DR

“Tree moors” does not appear to be a standard English term for tree roots in a particular English-speaking country or region; it looks nonstandard or mistaken.