When you choose trees, some of them has an S for solid, you have to uncheck that S otherwise they will hit. The big dead tree you use so frequently here doesn't make the terrain look natural. Try with a mix of many different trees instead of a few.
don't forget to take out the solid mark! (where you select the trees you can set this as standart for this kind of tree) ... you find it on catchingfeatures.com - library - cf maptiles