In this FACTivity, you will determine whether trampling has an effect on plants by simulating different conditions. Materials: Four shoeboxes or similarly sized boxes, lined with plastic Four squares of dirt, grass, and weeds dug up to fit the boxes Ruler Plastic bottle filled with water Aluminum can filled with sand or small rocks and taped shut Aluminum can (empty) Topics: Active Forest Management, Recreation, Experiment, Hands-on, Human Impacts, Modeling, Outdoor Activity, Vegetation.