Complex sentence: The main woodland areas were probably present as relic scrub woodland (similar to the semi-natural woodland pasture at Jack Scout)--the species forming the core of Sunside Wood and the other semi-natural woodland will have survived from the open common wood pasture.
Split into simpler sentences: The main woodland areas were probably present as relic scrub woodland similar to the semi-natural woodland pasture at Jack Scout. The species forming the core of Sunside Wood and the other semi-natural woodland will have survived from the open common wood pasture.