Complex sentence: It was established in 1974 (became a part of the Carpathian biosphere reserve in 1997) and aimed to preserve the oak-groves, formed by many heat-loving Balkan and Mediterranean species.
Split into simpler sentences: It was established in 1974 and became a part of the Carpathian biosphere reserve in 1997. It aimed to preserve the oak-groves formed by many heat-loving Balkan and Mediterranean species.