Forest ecology is the scientific study of the interrelated patterns, processes, flora, fauna, funga, and ecosystems in forests. The management of forests is known as forestry, silviculture, and forest management. A forest ecosystem is a natural woodland unit consisting of all plants, animals, and micro-organisms (biotic components) in that area functioning together with all of the non-living physical (abiotic) factors of the environment.

Forests have an enormously important role to play in the global ecosystem. Forests produce approximately 28% of the Earth's oxygen (the vast majority being created by oceanic plankton), they also serve as homes for millions of people, and billions depend on forests in some way. Likewise, a large proportion of the world's animal species live in forests. Forests are also used for economic purposes such as fuel and wood products. Forest ecology therefore has a great impact upon the whole biosphere and human activities that are sustained by it.

Forests are studied at a number of organisational levels, from the individual organism to the ecosystem. However, as the term forest connotes an area inhabited by more than one organism, forest ecology most often concentrates on the level of the population, community or ecosystem. Logically, trees are an important component of forest research, but the wide variety of other life forms and abiotic components in most forests means that other elements, such as wildlife or soil nutrients, are also crucial components.

Forest ecology shares characteristics and methodological approaches with other areas of terrestrial plant ecology, however, the presence of trees makes forest ecosystems and their study unique in numerous ways due to the potential for a wide variety of forest structures created by the uniquely large size and height of trees compared with other terrestrial plants.^{[citation needed]}

Forest pathology is the research of both biotic and abiotic maladies affecting the health of a forest ecosystem, primarily fungal pathogens and their insect vectors. It is a subfield of forestry and plant pathology.

Since trees can grow larger than other plant life-forms, there is the potential for a wide variety of forest structures (or physiognomies). The infinite number of possible spatial arrangements of trees of varying size and species makes for a highly intricate and diverse micro-environment in which environmental variables such as solar radiation, temperature, relative humidity, and wind speed can vary considerably over large and small distances. In addition, an important proportion of a forest ecosystem's biomass is often underground, where soil structure, water quality and quantity, and levels of various soil nutrients can vary greatly. Thus, forests are often highly heterogeneous environments compared to other terrestrial plant communities. This heterogeneity in turn can enable great biodiversity of species of both plants and animals. Some structures, such as tree ferns may be keystone species for a diverse range of other species.

A number of factors within the forest affect biodiversity; primary factors enhancing wildlife abundance and biodiversity was the presence of diverse tree species within the forest and the absence of even aged timber management. For example, the wild turkey thrives when uneven heights and canopy variations exist and its numbers are diminished by even aged timber management.

Forest management techniques that mimic natural disturbance events (variable retention forestry) can allow community diversity to recover rapidly for a variety of groups including beetles.