South
Ooops, not that kind of Direction...
ALL skills, not just LJ, get REALLY slow between 90 & 95-96. It is an artifact of the way the skill system was set up. It's especially bad for the skills that only go to 100. Consider trying to get up to 95, then acquiring a melisande's corroded hatchet to take you to 100 - after all, it doesn't raise your skill to 105, if used at 100, the way mining gloves do for mining.
Wood (and ore, for mining) are divided into 8x8 "resource squares" - no matter what tree you hit in a specific square, you'll get the same wood type, until you run it dry (same goes for ore when mining that spot).
The type of tree you hit has noting to do with the wood type or amount you get, and of course, the woods change randomly in the same area after you log it a few times. I once had a yew tree that straddled the line between resource squares, that gave oak on one side, ash on the other.
The only real constant for a resource square is the amount of wood that the square gives up. It will range in the same amount (give or take about 20%) every time, despite what wood the tree actually gives, as long as the tree has fully recovered from the last logging attempt.
Your best bet for finding good sources of wood is to just go out exploring, and when you find a tree that gives out 200 or more logs, mark the spot (or have a sextant, use it to get the coordinates, then take a mage out later to mark that spot), and build a library of high-output trees.
Most loggers are a bit stingy with their good locations - after all, since the wood type changes randomly, someone else could change their good tree from frostwood to normal - but if you keep logging the same good trees over and over, you will eventually get all the wood types.