How do you plan to pound the posts into the pond basin?

For the trees with branches, I've found in one pond that it takes about 2-3 years for a tree to reduce to the trunk and a few of the bigger branch stubs. That's for Christmas trees.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."