1. Flood plain - occasional or periodic flooding is needed to refresh certain nutrients and promote the life cycles of certain species of plants, animals, and soil organisms.
The ecosystem can be disrupted by "flood control" measures, such as dam building, or by flood-altering measures such as deforestation or pavement.
2. Prairie - the rich diversity of life it supports depends on the burrowing, foraging, and grazing animals who live there, as well as the interaction between plant species of different height, depth, and need for water.
The ecosystem can be disrupted by killing off large grazing animals or by fences that prevent their movement. "Sod-busting" for farming or construction also destroys this ecosystem.
3. Forest floor - this ecosystem provides for nutrient support, pest control, and communication between the plants and animals who live there. The largest known organism on Earth (a fungus) lives under forest soil.
The forest ecosystem is badly disrupted by logging, fire control, and other "management" techniques, as well as by paving, construction, and overuse by people. Reforestation projects may put more trees in the ground, but they don't restore the ecosystem. ("The Hidden Life of Trees" is a good book on this subject.)
