Introduction to the forest and rangeland ecosystems

A forest is an area of land dominated by trees.[1] Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological function.[2][3][4] According to the Food and Agriculture Organization definition, a forest is defined as land spanning more than 0.5 hectares with trees higher than 5 meters and a canopy cover of more than 10 percent, or trees able to reach these thresholds in situ. It does not include land that is predominantly under agricultural or urban land use.[5]

Forests are the dominant terrestrial ecosystem of Earth, and are distributed around the globe.[6] Forests account for 75% of the gross primary production of the Earth's biosphere, and contain 80% of the Earth's plant biomass. Net primary production is estimated at 21.9 gigatonnes carbon per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.[6]

Forests at different latitudes and elevations, and with different precipitation and evapotranspiration[7] form distinctly different biomes: boreal forests around the poles, tropical moist forests and tropical dry forests around the Equator, and temperate forests at the middle latitudes. Higher elevation areas tend to support forests similar to those at higher latitudes, and amount of precipitation also affects forest composition.

Human society and forests influence each other in both positive and negative ways.[8] Forests provide ecosystem services to humans and serve as tourist attractions. Forests can also affect people's health. Human activities, including unsustainable use of forest resources, can negatively affect forest ecosystems.[citation needed]

Rangelands are grasslands, shrublands, woodlands, wetlands, and deserts that are grazed by domestic livestock or wild animals. Types of rangelands include tallgrass and shortgrass prairies, desert grasslands and shrublands, woodlands, savannas, chaparrals, steppes, and tundras. Rangelands do not include forests lacking grazable understory vegetation, barren desert, farmland, or land covered by solid rock, concrete and/or glaciers.

Rangelands are distinguished from pasture lands because they grow primarily native vegetation, rather than plants established by humans. Rangelands are also managed principally with practices such as managed livestock grazing and prescribed fire rather than more intensive agricultural practices of seeding, irrigation, and the use of fertilizers.

Grazing is an important use of rangelands but the term rangeland is not synonymous with grazingland. Livestock grazing can be used to manage rangelands by harvesting forage to produce livestock, changing plant composition, or reducing fuel loads.

Fire is also an important regulator of range vegetation, whether set by humans or resulting from lightning. Fires tend to reduce the abundance of woody plants and promote herbaceous plants including grasses, forbs, and grass-like plants. The suppression or reduction of periodic wildfires from desert shrublands, savannas, or woodlands frequently invites the dominance of trees and shrubs to the near exclusion of grasses and forbs.