Which environmental conditions prevent trees and shrubs from taking over grasslands?

Grasslands are maintained by a dynamic balance of environmental conditions and disturbances that prevent woody plants from establishing dominance. Key factors include:

• Disturbances: Regular fire and heavy grazing are critical. These disturbances kill or suppress the growth of trees and shrubs, allowing grasses—which are well-adapted to recover from such events—to flourish.123
• Climatic Constraints: Many grasslands exist in regions where the growing season is too short or the climate is too dry for forest development. In high-latitude or high-altitude areas, temperatures may be too cold for trees to grow.13
• Hydrological Factors: Seasonal flooding or waterlogging can prevent woody vegetation from taking root, creating and maintaining large grassland areas.1
• Soil Conditions: In environments where the climate might otherwise support forests, very shallow or infertile soils can inhibit tree growth, favoring the development of grassland instead.1

In the absence of these limiting factors, woody plants may shade out grasses and lead to a transition toward savanna, scrubland, or forest through ecological succession.23