A while back I described how I was showing tree types in woodland. The “unfinished business” there was “what about forest areas where the trees have been cleared?”. Mapping of that is a bit hit and miss. “Forestry” has been suggested, but doesn’t have many takers, and “forest” is actually often used for “the entire forestry area” (at least where I’m interested in rendering tiles for - I suspect it varies considerably worldwide). The wiki page and the standard style rendering discussion don’t distinguish, but I thought it was worth trying to separate out “natural=wood” and “landuse=forest” where the latter is used for “the entire forestry area, including where there are currently no trees”.

Here’s the result:

That corresponds to here in OSM’s standard style. The dark green bit corresponds to “trees” (natural=wood; if there’s a surveyed leaftype then obviously that is shown too). The lighter green bit means “forest, but no trees” (landuse=forest - the lighter green is only visible if there’s no natural=wood also there). The forest and wood colours are defined here; here is the leaf_type handling in the stylesheet and here is where the natural and landuse tags are checked to see whether the current object should be treated as “trees with a known leaf type”, “trees without a known leaf type” or “forest, but not necessarily trees”.