Chui Wui Jing/ShutterstockRising more than 70 metres above the rainforest canopy, a giant skyscraper of a tropical tree can seem almost invincible. Some have survived centuries of storms, droughts and competition. Large trees face a formidable engineering challenge, lifting water tens of metres from the soil to leaves high above the forest floor. A challenge which intensifies during drought. But are giant trees uniquely vulnerable to drought or …