In a forest ecosystem, green plants are

Autotrophs are another term for primary producers. They obtain their energy from the Sun and their resources from non-living things. Green plants, algae, and lichens are among the primary producers. They convert sunlight into energy through photosynthesis. 

Consumers are biological organisms that obtain energy from various food chains. Since they are unable to manufacture food, they must obtain food from other sources, or make food from other species.

The organism that consumes the producers is known as a primary consumer. Herbivores are the primary consumers.

The organism that decomposes both dead animals and plants is known as a decomposer. Bacteria and protozoa, for example, are the primary decomposers in an ecosystem.