Many of you have been frustrated that you can't control the density of autogen trees verses buildings because we only have one slider to cover both of them. Some have also been frustrated that our lowest autogen setting is more dense than FS2004 at max density.
If you add these two lines to the [TERRAIN] section of your FSX.CFG, you can define the max number of objects in a terrain cell for trees and buildings independently. The slider will scale down from the numbers you set as the slider is moved to the left. The max tree value in FSX as released is coded to default to 4500 and the building default is 3000 (as shown below) and the absolute max FSX will recognize at all is 6000. Of course if you raise the values beyond the defaults, you will obviously be increasing density and lowering fps (so don't complain if you do this...). The point in sharing this information is that with these settings you can specify what the values are yourself. I had to edit this post because of a bug. Be sure not to set either number to 0 as that will cause problems, but setting it to a very lower number will give you nearly 0 objects.
I hope this is helpful!