A question has bedeviled a wealthy Lake Tahoe enclave for years: Who is poisoning the towering trees that stand sentry on the North Shore?

Residents of Incline Village, Nev., hope a $147,000 reward will generate some answers.

"It's the most appalling, selfish thing that anyone could do, especially for trees that are irreplaceable," said Chris Nolet, a retired certified public accountant and consultant to the biotechnology industry who assembled a small group of private donors known as Friends of Burnt Cedar Beach to put up the bulk of the reward. "These trees are 100 years old."

The donors are offering $122,000 for information leading to the successful prosecution of anyone responsible. The Incline Village General Improvement District, which owns and manages the residents-only beach where the poisonings took place, has put up another $25,000 and installed additional cameras around the trees.

The move c...