Timber is valuable and xmas trees are not. Most people don't think about that in the planning process. Most ponds make use of the stumps and rootball piles to do the same thing. Bottom contours in the construction also work.

See the article in PB mag earlier this year in the Cutting Edge on aging ponds and reservoirs and why standing timber (like all new environmental enhancements) is productive but with age is not so much.

We left some standing timber in our ponds but also use xmas trees and other enhancements.