The more dense a woods are, the lower the sugar %.
Sugar is made by the leaves, thin the woods and the % will rise.
That being said, the sap sugar % varies by the season and even by the day. 2 years ago we had our lowest sugar % ever, (it averaged 1.2%) last year we averaged just over 2%. Since no thinning had been, the difference was the previous year's weather, it had been very rainy the season before 2018 for much of the summer, for the 2019 season it started quite rainy be then dried out with lots of sun.
You will get your best sap sugar % when you have good crowns and a good balance of rain and sun. While you can't change the weather, you can remove some of the trees competing for the sun. A word of caution, do not cut too mny at once. If a tree had lots of competition and you remove the competition, the tree left may have sun and wind damage. You are best off opening just 1 side, then wait 2-3 years before you open up another side. That gives the remaining tree time to fill in some of the open space at the canopy and also strengthen to hold up against the extra wind.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.