Complex sentence: Tighnabruaich has a special association with the Australian Army, as the residence of the generals commanding the Army in Queensland for close to half a century; trees planted by the resident generals remain as evidence of that association.
Split into simpler sentences: Tighnabruaich has a special association with the Australian Army as the residence of the generals commanding the Army in Queensland for close to half a century. Trees planted by resident generals remain as evidence of that association.