Rate of tree carbon accumulation increases continuously with tree size

Area of Science:

• Forest ecology
• Global carbon cycle research
• Plant physiology

Background:

• Forests play a critical role in the global carbon cycle, influencing atmospheric greenhouse gas levels.
• Accurate modeling of forest carbon dynamics requires understanding biological processes across multiple scales.
• There is a lack of consensus on individual tree productivity as trees grow larger and older.

Purpose of the Study:

• To empirically assess how individual tree mass growth rates change with tree size and age.
• To resolve conflicting assumptions about tree growth patterns.
• To inform forest carbon cycle models and theories of plant senescence.

Main Methods:

• Global analysis of 403 tropical and temperate tree species.
• Examined the relationship between tree size and mass growth rate.
• Investigated factors explaining apparent paradoxes in tree growth.

Main Results:

• For most species, tree mass growth rate continuously increases with tree size.
• Large, old trees actively accumulate substantial amounts of carbon.
• A single large tree can sequester as much carbon annually as a mid-sized tree.

Conclusions:

• Large trees are not merely senescent reservoirs but significant carbon sinks.
• Increased total leaf area, despite declining leaf-level productivity, drives growth in large trees.
• Findings impact forest carbon modeling, resource allocation theories, and plant senescence understanding.