Imagine that a farm is abandoned and living things are allowed to grow without human intervention. what type of plant communities would you expect to grow in the area, and how would they change over time?

If there were no human intervention in plant ecosystems, most probably we will have a thick and lush plant ecosytem. Soil can be richer compared to the soil that we have now.
However, if there are no human intervention, there will be an imbalance. There will be no consumers. It is important that there should be a balance in any type of eco system.