Photosynthesis and decay are the two most essential processes in nature. Photosynthesis by green plants captures and stores energy from the sun. This energy is used to form wood and other tree parts. Photosynthesis also removes carbon dioxide and adds oxygen to the atmosphere. Decay releases stored energy and essential elements by the breakdown of wood. Fungi decay the wood in living and dead trees as part of a vital web of microorganisms, insects, and wildlife. Decay organisms enter trees through wounds, large and small. Trees have survival strategies that can resist the spread of decay.