Ali Alishah, 28, appeared in the Hobart Magistrates Court charged with breaching a three-month suspended sentence.

One campaigner said Alishah was the first forest activist to be sentenced to prison in Tasmania for a non-violent protest.

The breaches related to protests that included blocking a truck from entering the proposed pulp mill site at Bell Bay and locking on to a crane to prevent a Malaysian ship from loading veneer in Hobart.

Magistrate Chris Webster said the breaches were serious.

``They endangered the safety of others and yourself,'' he said.

Alishah's lawyer, Roland Browne, said his client had an extensive record between 2008 and September last year for offences such as trespass and committing a nuisance.

But he said Alishah had not offended since he was remanded in custody for five weeks and four days from September 5 last year.

``His time in prison had a particularly sobering effect upon him,'' Mr Browne said.

Mr Browne said his client continued to have a ``burning concern'' for forestry issues but that he would campaign for the protection of forests in ways that did not breach the law.

Alishah was sentenced to three months' prison, less the time he spent in custody last year.

He received a three-month suspended sentence for one count of trespass on the condition that he be of good behaviour for two years. He is also disqualified from holding a driver's licence for three months due to a traffic offence he committed during the period he was required to be of good behaviour for the original suspended sentence.

The Huon Valley Environment Centre's Jenny Weber said she believed it was the first time an environmentalist had received a custodial sentence.

Ms Weber broke down outside the court after Alishah was sentenced and said non-violent, peaceful action against logging would continue.