Tree water uptake patterns across the globe.

Area of Science:

• Ecology
• Hydrology
• Plant Physiology

Background:

• Plant water uptake is vital for the global water cycle and vegetation drought resilience.
• Understanding water uptake depth (WUD) distribution across diverse environments remains limited compared to aboveground plant functions.

Purpose of the Study:

• To synthesize global knowledge on plant water uptake depth (WUD).
• To investigate factors influencing WUD variation across species, climates, and seasons.
• To compare WUD with rooting depth and assess its implications for drought resilience.

Main Methods:

• Global literature review of plant water uptake depth studies.
• Analysis of WUD variation across biomes and plant functional types.
• Integration of rooting depth data with WUD to understand water acquisition strategies.

Main Results:

• Average WUD variation was greater among biomes than plant functional types, highlighting hydroclimate influence, particularly precipitation seasonality.
• Maximum rooting depth consistently exceeded WUD, with the largest discrepancies in arid regions, suggesting deep roots serve as a lifeline rather than primary water source.
• Woody plants demonstrate a ubiquitous ability to rapidly switch water sources to available soil layers, including seasonal shifts to deeper soil during shallow soil drying.

Conclusions:

• Hydroclimate, especially precipitation patterns, significantly shapes plant water uptake depth.
• Deep root systems provide hydraulic safety and drought resilience, even if not the primary water source.
• Despite knowledge gaps, consistent global patterns in WUD support integrating this understanding into vegetation process models.