Root vascular traits differ systematically between African savanna tree and grass species, with implications for...

Area of Science:

• Plant Ecology
• Root Biology
• Savanna Ecosystems

Background:

• Belowground functional traits influence plant water-use strategies and performance.
• Limited data exists on root traits across communities, especially in tropical savannas.
• Tree-grass functional differences in water use are hypothesized to drive savanna vegetation dynamics.

Purpose of the Study:

• To investigate root vascular anatomy traits in savanna trees and grasses.
• To compare root trait differences between tree and grass species.
• To test for phylogenetic signals in root traits.

Main Methods:

• Grew 21 tree and 18 grass species from southern African savanna under greenhouse conditions.
• Collected fine-root segments for histological analysis of xylem vessels.
• Quantified six root vascular anatomy traits and tested for phylogenetic signals and tree-grass differences.

Main Results:

• Grass roots possessed larger xylem vessels, a higher proportion of vessel area, and greater estimated axial conductivities than tree roots.
• Trees had a higher number of vessels per root cross-sectional area compared to grasses.
• Phylogenetic relatedness was associated with trait values in most tree species, but not grasses.

Conclusions:

• Grass roots demonstrate higher water transport capacity, supporting their role as more "aggressive" water users under high soil moisture.
• Root functional traits identified may drive differential responses of trees and grasses to soil moisture availability.
• Findings contribute to understanding savanna ecosystem dynamics driven by water-use strategies.