The deliberate poisoning of 30 to 40 native trees at a Kinloch reserve has been labelled "eco-terrorism".
Kinloch Community Association president Belinda Walker said the community was outraged.
The dying kahikatea trees in the Whangamata Stream Scenic Reserve were discovered by weed contractor Peter Marshall last month while doing weed control with Kinloch locals.
Closer investigation showed drill marks in the trees' trunks. He said he had reported the vandalism to the Department of Conservation.
Marshall said locals told him there had been a request to have the trees removed.
DOC said in a statement there was speculation the trees had been killed so that they would not grow tall enough to obstruct views from nearby properties.
Marshall, who has been involved in restoring the reserve, once pasture, since the late 1980s, said it was "heartbreaking" to see the work undone. Only kahikatea trees were found to have been poisoned.
The kahikatea were between 6m and 7m tall but can grow to 55m.
It is an offence under the Reserves Act 1977 to cut or destroy trees and bush without a permit, and while many other trees and shrubs have been illegally cut and trimmed in the DOC reserve, this latest act is the worst since the reserve came under DOC management in 1987. Other trees in the reserve have been severely pruned to allow lake views.
Walker said it was "massively, massively disappointing" to see the trees, more than 30 years old, slowly dying and she asked that anybody with information about who may be responsible contact Dave Lumley at DOC.
"If by some miracle anything is known, then it could be a police investigation," she says.
In 2013 a spate of tree poisonings occurred at Kinloch, with a number of trees on council land dying. The poisoner was eventually caught in the act and prosecuted.
Walker said the community association understood there had been requests to DOC to top the trees on the reserve. She said an upcoming issue was the safety of the ageing poplars that were also part of the same reserve but which are protected by their listing as notable trees.
DOC operations manager for the Central Plateau District Dave Lumley says it was a real concern that significant vegetation on public conservation land had been treated in this manner.