Look at the wonderful ecosystem, the forest. Have you ever wondered how this large community came to be? With so many organisms and a large biodiversity, it's a perfectly balanced ecosystem. Well, I'll show you what made this ecosystem be the way it is now.
This is where a natural disaster occurred, a volcano eruption. Now everything is destroyed to only barren land. Causing the land to go through ecological succession.
This is the barren land, and primary succession is going to start to occur. There are no biotic factors, everything is abiotic, (rocks) with no life. There are very slow changes.
This is the stage of primary succession, and the pioneer species, lichens, are starting to grow. Now, rocks are starting to break down due to weathering.
This is the stage of secondary succession, more biotic factors are starting to show. There are more fast changes now that there is soil. There are now producers like grass and bushes.