One of the central concepts of natural science is the ecosystem. The prefix "eco-" derives from the Greek and Latin word for "house," and the word "system," as biologist Tamara Harms explains, means that "not only do the parts exist together as if they were in one house, but the parts also affect one another." Some of these parts are living, or biotic, and some are nonliving, or abiotic. Forests contain both types of factors.
Biotic Factors by Type
The most obvious features of any forest ecosystem are its trees, the dominant biotic feature. They dominate the ecosystem, both in terms of visibility and in terms of biomass, but they are only one type of organism living in a forest. Other biotic factors include shrubs, flowering plants, ferns, mosses, lichens, fungi, mammals, birds, reptiles, insects, worms and microbes.
Abiotic Factors by Type
The most obvious abiotic feature of a forest ecosystem may not be obvious, despite its ubiquity and importance: sunlight. Tangible abiotic factors include soil, minerals, rocks and water. But abiotic factors can be intangible, such as temperature, other types of radiation, and the chemistry of soil and water.
Biotic Factors by Function
Ecologists frequently group an ecosystem's factors by what role they play in the system, rather than by what particular species they are, known as functional classification. These functions relate to the movement of energy through an ecosystem, and trees--along with other photosynthetic plants--are the chief primary producers. This means that they convert the sun's energy into food energy, which is used by other members of the ecosystem; those include primary consumers, herbivores that eat the primary producers, secondary consumers, carnivores and omnivores that eat the primary producers, and decomposers, the scavengers, microbes and fungi that "consume the droppings and the carcases" of other organisms.
Abiotic Factors by Function
The abiotic factors of a forest fall less obviously into functional classifications, but keep in mind that the energy transferred among the various biotic categories is itself a foundational abiotic element. This energy occurs in the form of solar radiation, which includes both visible light and heat (infrared); primary producers convert the light into carbohydrates, a form of energy that can be consumed by other organisms. The function of other abiotic factors relies on the minerals they contain, such as the nitrogen in the soil or the hydrogen in water molecules.