The deceased has been named as Owusu Arhin, 35, who until his death was stationed at the Mankranso Police post.
A 55-year-old chainsaw operator, Isaac Gyan, is being detained and questioned over the incident which occurred at about 12 noon in the Ahiamankwa Forest near Kunsu Wioso in the Ahafo Ano South District.
The suspect was using a chainsaw to cut up the tree when the enormous trunk fell on top of the victim, the police said.
Emergency services rushed to save the man, but he was pronounced dead at the scene.
A similar incident had earlier occured on Saturday at Motiakrom in the Upper Denkyira East Municipality of the Central Region.
The deceased, Eric Ntam, was seeking shelter under a tree during a downpour when the trunk eventually fell on him, witnesses say.
By Jonathan Ofori, Daily Mail GH