Forest Age Rivals Climate to Explain Reproductive Allocation Patterns in Forest Ecosystems Globally

Area of Science:

• Ecology
• Forest Science
• Biogeochemistry

Background:

• Forest reproductive allocation (RA) is crucial for regeneration but globally unquantified.
• A trade-off exists between RA and growth, impacting ecosystem dynamics.
• Existing vegetation models often assume a fixed global RA fraction of net primary productivity (NPP).

Purpose of the Study:

• To synthesize global data on forest reproductive allocation (RA).
• To investigate environmental and stand-age drivers of RA.
• To improve vegetation and ecosystem models by challenging fixed RA assumptions.

Main Methods:

• Compiled a global dataset of 824 observations from 393 sites.
• Used a biometric proxy for ecosystem-scale reproductive allocation (RA).
• Analyzed RA across environmental (climate, soil) and stand-age gradients.

Main Results:

• Ecosystem-scale RA increases by ~60% from boreal to tropical forests.
• Climate, forest age, and soil fertility significantly influence RA.
• RA magnitude is comparable between climate and forest age effects.
• Soil pH and nitrogen show smaller but significant relationships with RA.

Conclusions:

• Ecosystem-scale RA is mediated by climate, forest age, and soil conditions.
• RA is not a fixed global fraction of NPP as commonly assumed.
• Findings and dataset can enhance predictions of forest regeneration and carbon cycling.