Buccleuch Estates Limited admitted failing to observe proper guidelines, which could have prevented the death of Ross Findlay at Bogrie Wood near Drumlanrig Castle in Dumfries.
Mr Findlay, who had learning difficulties, was killed when he was crushed by a 216-foot tree that had been uprooted and knocked over by another tree that was being cut down.
An investigation was launched,leading to Buccleuch Estates Limited being prosecuted at Dumfries Sheriff Court for failing to properly assess the risk, provide safety equipment or a safe working environment.
Mr Findlay should have been at least two tree lengths away from the tree being felled. However, he was well within the exclusion zone when he was struck and killed.
HSE Inspector Aileen Jardine said: "This was an entirely avoidable incident and the failures by The Buccleuch Estate directly resulted in Mr Findlay's tragic death. A system of waves and nods is not a safe way to manage the felling of large, heavy trees … This informal and unsafe way of working had been in place unchallenged and not updated for over 15 years, with the estate making no efforts to follow industry safety guidelines or to even accurately assess the risks its workers faced."
A Buccleuch Estates spokesman said: "Buccleuch Estates deeply regrets that the implementation of safety provisions that were in place at the time failed to prevent the accident."