Can you provide more information about the map?
I would also suggest to use different tree models as Sonofjay mentioned, they simply do not fit. Use some different elevation and smooth out the terrain.
That cave (if it is a cave) looks... well It just does not fit, use the rocks to make a cave entrance, the same ones you used to create the mountain.
On the 'ocean' terrains there is just too much foliage so of that should be deleted, its just too crowded. You can either delete some of them or place them in a better way.