Answer:
If producers were removed from an ecosystem, there would be no beginning to the food chain, thus the rest of the ecosystem would die off. This is because plants sit at the beginning of the food chain. Many primary consumers depend on this, thus if it died off, so would the primary consumers, and then the rest of the food chain dies off as well. If decomposers were removed from an ecosystem, there would be no organic nutrients decomposing all the dead plants and animals, which would then fill the ecosystem up with dead plant and animal wastes. This is because there is no decomposition of waste material.
Hope this helped!