Sapflow Database Reveals Density-Dependent Competition Among Woody Plants at Global Scale

Area of Science:

• Ecology
• Plant Physiology
• Global Change Biology

Background:

• Water is a critical limiting resource in many ecosystems, driving inter-plant competition.
• Measuring plant water uptake offers a direct method to assess competition.
• Sapflow measurements, while direct, have not been extensively used to study large-scale competition.

Purpose of the Study:

• To investigate density-dependent competition for water using a global sapflow database.
• To determine if plant-level water uptake is influenced by neighboring plant density.
• To explore the relationship between sapflow, environmental factors, and competition at a global scale.

Main Methods:

• Utilized the SapFluxNet database, a global collection of sapflow measurements.
• Analyzed plant-level water uptake in relation to neighborhood basal area as a proxy for competition.
• Applied statistical models to explain global sapflow variability using environmental variables and competition metrics.

Main Results:

• Plant water uptake significantly decreases with increased neighborhood basal area, indicating competition.
• Global annual sapflow variability is substantially explained by average vapor pressure and summed neighborhood basal area (R² = 0.522).
• This study provides direct evidence of competition for water inferred from resource acquisition measurements.

Conclusions:

• Sapflow measurements are a viable tool for quantifying plant competition at large scales.
• Density-dependent competition for water is a significant factor influencing plant water use globally.
• Environmental factors like vapor pressure interact with competition to shape plant water uptake patterns.