Terrains up to and including Vue 8 have always been very small - 28ftx28ft which a mountain does not make.  So trees will look huge.  On the world browser, you can see the size of your terrain - scale it up to the size you require.

Poser imports always come in huge.  A 6foot human does not import at 6foot.  

As Bruno rightly says, just resize the objects to what you need

Gill