It seems like it is the relationship with God that empowers. He transfers life to us when we go into His presence. It flows into our hearts. From there, those who continue in His presence can bear fruit and allow life to flow to others.
If we are not connected to the flow, we dry out. The ground around us becomes hard, and difficult to grow anything worthwhile.
If we are connected, we can produce fruit in any circumstance. It is compared to a tree thriving in the desert, because it is planted along a river. It can draw life from the river.