In an apparent protest against the removal of trees in Northbourne Avenue, white crosses have been installed at the site of felled trees over the past week or more.
A spokeswoman for Territories Minister Meegan Fitzharris said the crosses were being removed as they appeared. To date, four had been removed.
The government felled 42 trees over five days in April, saying they were dying and diseased, and so unsafe. It spent $32,000 on the removal.
It is not known who is placing the crosses on the site of downed trees, but if it is a campaign or protest it could become a headache for the government as entire blocks of trees begin to be felled to make way for the tram later this year.
The Canberra Metro consortium will cut down all 444 remaining trees on Northbourne Avenue, felled in tranches as work progresses.
They will be replaced with 4-metre high trees that are expected to "approach maturity" – 10 to 20 metres high – within 10 or 15 years of planning.
Ms Fitzharris's spokeswoman said the trunks of the 42 unsafe trees removed were being used in the Molonglo Valley to provide new homes for some endangered box-gum woodland invertebrates, reptiles and birds.