18 May, 11:09
IRFU Chief Executive Philip Browne has issued a statement following confirmation of Ronan O'Gara's decision to retire from playing professional rugby.
Black suffered with a neck injury in his first campaign with the province but has featured in seven games already this season, bringing his total tally to 16 appearances.
He will provide long term competition for Tom Court and Paddy McAllister for the starting loosehead prop position.
Meanwhile, South African hooker Rob Herring is also Irish-qualified and has committed his future to Ulster after signing for an initial one-year period in the summer.
So far this season he has battled it out with Nigel Brady for the role as back-up to Ireland international Rory Best. He has made six competitive appearances for Ulster to date, including two RaboDirect PRO12 starts.
Commenting on the contract extensions, Ulster's director of rugby David Humphreys said: "We have demonstrated the importance of having a strong squad so far this season with a large number of players contributing to an unbeaten start.
"The signings of Callum and Rob on long-term deals is a boost to the province and both will play an important part as we aim to build a squad capable of challenging for silverware in both the RaboDirect PRO12 and Heineken Cup."
Herring said: "I'm delighted. I've settled in really well and it was quite an easy decision in the end. To be honest, when I first signed I didn't think I would get such a good run of games but I want to keep improving every week and use the opportunities that I get to make an impact.
"I'm glad to be part of the team, we are building something big. We are aiming to win silverware in both competitions and we will be working hard towards that."
Black added: "I had a difficult first season with Ulster, getting injured at the start, but I've recovered and have thoroughly enjoyed being part of a successful Ulster squad.
"We did well last year, reaching the final of the Heineken Cup. But this season we really believe we can get into the top four in the PRO12 and into the knockout stages of the Heineken Cup again."