Excellent composition!
I really have no criticism, except to say, some of use add some translucency (pale pastel of leaf color) , a
little specularity, and reduce the opacity mask to just above 0.5. We do this to mimic other texture techniiques found in other 3D software, that are not available in Terragen. See the Materials Library in File Sharing, esp. Hannes' material file share for metals, flesh, stone, wood....WASasquatch also has a
current material file share in the works.
Ask a question in Discussion, as you did, and someone will give you help.
If I have not gone completely mad yet, you won't either!