It took me a while to spot your problem, but you mean the boxes the appear around the trees.
That is because you have used 'billboard' style (flat) trees.
I don't do a lot of renders but using 'physical' render settings should help.
I found this post that might help you out.
https://archicad-talk.graphisoft.com/viewtopic.php?f=3&t=54709
Barry.
One of the forum moderators.
Versions 6.5 to 27
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