Why do grasslands usually have few trees?

Grasslands generally have few trees due to a dynamic balance of environmental factors and disturbances that favor grasses over woody vegetation. The primary reasons include:

• Climatic Conditions: Grasslands often exist in regions where moisture is insufficient to support the dense, tall vegetation of forests but enough to prevent the barrenness of deserts. In many areas, seasonal dryness or drought limits the survival of trees, which typically require consistent water access.12
• Disturbances: Frequent wildfires and grazing by herbivores are critical in maintaining grasslands. While many savanna trees have evolved thick bark to survive fires, frequent burning can prevent woody plants from establishing or spreading. Similarly, grazing animals can suppress tree growth, and in some cases, human-led burning has transformed former forest lands into grasslands.1342
• Soil Characteristics: Soil type plays a significant role; for instance, shallow or infertile soils may be unable to support tree growth, allowing grasses to dominate. Conversely, sandy soils that dry out quickly favor grasses, while deeper, coarser soils may support more trees.12
• Environmental Extremes: In high latitudes or high-altitude regions, temperatures may simply be too cold for trees to grow, resulting in natural grasslands. Additionally, seasonal flooding or waterlogging can prevent woody plants from taking root, creating expansive grassland areas.1