How are forests, woodlands, savannas, and tundra different in tree cover?

These ecosystems are primarily distinguished by their density of tree cover and structural complexity:

• Forests: Defined by a closed canopy of trees that can range from 10 to over 50 meters in height. They are complex ecological systems where trees are the dominant life-form, creating distinct vertical strata.12
• Woodlands and Savannas: These are transitional zones between forests and grasslands. Savannas are characterized as open, grassed woodlands with a continuous grass cover that is only occasionally interrupted by trees and shrubs. While the distinction is often arbitrary, savannas generally have a more open structure than forests, with tree density influenced by factors like rainfall, fire, and grazing.31
• Tundra: Found at high latitudes and elevations, the tundra is a community of low-growing plants that replaces forests at their cooler or wetter limits. It is characterized by a lack of a closed tree canopy; instead, it features dwarfed shrubs, mosses, lichens, and perennial herbs. While "bushlike" trees may reach over 10 feet in sheltered areas near the tree line, the landscape is generally an open, rolling plain.14