The flow diagram shows how a forest is regenerated in a national park after being destroyed by fire. The following report describes the process in greater detail.

　　First of all, the forest is hit by lightning and a fire breaks out. The fire spreads quickly because the trees are very close together and there are also old pieces of wood lying on the ground and as a result the forest is completely destroyed by the fire. However, after the forest has been burnt down the ash from the trees fertilizes the soil and creates ideal condition for plant growth.

　　In the next 50 years seedlings from the trees begin to grow and the trees continue to grow until the forest is back to its former state, which takes 300 or more years.

　　In conclusion, forests can regenerate themselves, but it takes a long time and as forests are important for the environment, their protection is also important.