What does the putting black cloth over the beehive represent in The Secret Life of Bees? Death, life, the circle of life, or that the bees are sad?

The shrouding of the beehives is a symbol of mourning. The ancient Greeks placed shrouds over the beehives because they believed the bees represented the soul of the deceased, thus, representing the resurrection of the deceased's soul in the afterlife. Based upon these facts, I'd have to say the answer to your question is the circle of life.