Why do scrubland plants invest so much biomass in roots and underground organs?

Scrubland plants invest a significant portion of their biomass into extensive root systems, lignotubers, and other large underground organs primarily as an adaptation to harsh environmental conditions.1

These regions are characterized by high levels of stress, including long periods of hot, dry weather where moisture is a limiting factor for growth, as well as typically low soil nutrient levels. By maintaining a substantial underground structure, these plants can survive and recover from episodic disturbances, most notably fire, which is a regular feature in many scrubland environments.12

Because these plants often experience drought stress and nutrient scarcity, their overall biological productivity is relatively slow. The investment in underground organs allows them to store resources and persist during periods when aboveground parts may be damaged or when moisture is in short supply, ensuring the plant's survival in an environment where tree growth is often impossible.12