The scientific study of forest species and their interaction with the environment is referred to as forest ecology, while the management of forests is often referred to as forestry.
The forests of tropical mountains are also included in this broad category, generally divided into upper and lower montane formations on the basis of their physiognomy, which varies with altitude.
Tropical dry forests are characteristic of areas in the tropics affected by seasonal drought.
Forests are often home to many animal and plant species, and biomass per unit area is high compared to other vegetation communities.
Temperate broadleaf and mixed forests include a substantial component of trees in the Anthophyta.
More than 75 percent of these intact forests lay in three countries: the Boreal forests of Russia and Canada, and the rainforest of Brazil.
Mangrove forests also fall within this broad category, as do most of the tropical coniferous forests of Central America.
Temperate needleleaf forests mostly occupy the higher latitude regions of the northern hemisphere, as well as high altitude zones and some warm temperate areas, especially on nutrient-poor or otherwise unfavorable soils.
Forests sometimes contain many tree species within a small area (as in tropical rainforests and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests).
Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g.
Forests can also be classified more specifically based on the climate and the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).
Forests can be classified in different ways and to different degrees of specificity.
In 1997, the World Resources Institute recorded that only 20 percent of the world's original forests remained in large intact tracts of undisturbed forest Bryant et al.
Anthropogenic factors that can affect forests include logging, human-caused forest fires, acid rain, and introduced species, among other things.
The montane forests include cloud forest, those forests at middle to high altitude, which derive a significant part of their water budget from cloud, and support a rich abundance of vascular and nonvascular epiphytes.
Tropical moist forests include many different forest types.
Historically, "forest" meant an uncultivated area legally set aside for hunting by feudal nobility, and these hunting forests were not necessarily wooded much, if at all.
Sparse trees and parkland are forests with open canopies of 10-30 percent crown cover.
Some of the values of forests can be converted to commercial value, with trees providing timber for construction and housing, paper, firewood, and so forth.