This one is real simple. We used a small cardboard box, some cut out paper animals that my son colored plus some sticks and moss we found around the garden. We didn't worry about making it to scale, I just wanted to get him involved in the process.
I made 3D paper trees by following the instructions from Enchanted Learning, which is a great site for all kinds of homeschool help. The paper images are just taped down and we used colored construction paper to create the sky and ground.
I also printed out this chart to attach to the top for study. It shows an easy to understand complete picture of the food chain. The best part is we finished the whole thing in an afternoon and he was able to help.
Now he wants to make 100 more! I have a feeling we will have a whole wall of miniature scenes before long. Where on earth am I going to store all his school work?