More than 60 people gathered at the remote Forest & Bird Lenz Reserve at Tautuku, near Papatowai, to take part in presentations, bush walks, and a traditional ''Deep South'' afternoon tea.
In marking the anniversary, speakers looked both to the 50-year foundation of the facility brought about by ''tireless'' volunteers, and forward to a ''bright'' future for its 544ha of mixed podocarp forest, thanks to recent and continuing efforts in pest control and biodiversity studies.
Representing Forest & Bird's national body was board member Ines Stager, of Geraldine, who recalled her first visit to the reserve in the 1980s.
''I remember there were about 20 kereru swooping in the broom, which was amazing to see. Now I see there's no broom, but still plenty of kereru.''
Although Forest & Bird's core purpose was nature advocacy rather than land stewardship, the Lenz was a ''pristine'' asset, and its successful management was a tribute to southern members.
She said pest control would be key to enhancing biodiversity in the future.
To date, 210 species of plant had been catalogued, including 59 different ferns.
Fauna including falcons, Tautuku forest geckos, kakariki and ''an abundance of fernbirds'' had also been identified.
Although there was still work to be done controlling bush-destroying pigs and deer, extensive trapping of rats, stoats and possum since 2014 was helping native fauna thrive.
Forest & Bird South Otago member Jim Young said there were now 512 predator traps in and adjoining the reserve, which, to date, had caught a total of 891 rats and 146 stoats.
Volunteers had just begun installing a further 100 predator traps, and pig and deer traps were also being trialled.
In a fitting conclusion to ceremonies, Lenz Reserve management committee chairman Fergus Sutherland and Invercargill Forest & Bird volunteer Neil Coaley planted a rimu sapling between the reserve's cabins.
