Phew! Last two - please help parse:
3D) Two men in a boat died there (6)
I have A?O?R?.
It looks like ABOARD, but I dunno why.
8D) Presiding officer imprisons indigenous Aussie (5)
I have D?N?O, and presume it’s DINGO, but again, pourquoi??
(The overarching theme is trees, but I think not with these two.)