Why do shrubs dominate vegetation in many scrublands instead of trees?

Shrubs dominate vegetation in many scrublands because these environments present challenging conditions that are generally unsuitable for the growth of trees, yet still adequate to support shrub species.12

The primary factors influencing this vegetation structure include:

• Climate Stress: Many scrublands occur in regions with significant moisture shortages, such as areas with a Mediterranean climate characterized by hot, dry summers and mild, wet winters. In these regions, high evaporation rates and seasonal drought stress make it difficult for trees to thrive. Similarly, in high-latitude or alpine regions, cold temperatures or short growing seasons can preclude tree growth, leaving shrubs as the dominant vegetation.13
• Soil Conditions: In some areas, nutrient-poor or otherwise challenging soils are the primary factor preventing tree development, favoring plants adapted to these specific limitations.1
• Environmental Disturbances: Frequent fire regimes are a common feature of many scrubland environments. While some trees have evolved fire-resistant traits, the overall community structure in these areas is often maintained as scrubland by the frequency of these events. Conversely, human activities like fire suppression can sometimes shift these communities toward woodland, while overgrazing can shift them toward grassland.13

In these habitats, shrubs have evolved specific adaptations to survive drought, fire, and nutrient-poor soils, allowing them to persist where trees cannot.3