Functional biogeography of root traits from deserts to tropical forests
Large-scale patterns of plant functional traits are receiving increasing attention for their importance in understanding biogeography of species distributions and ecosystem functions. The biggest gap in this field is probably the understanding of how root functional traits vary across different biomes and the mechanisms driving this variation. Here, we analyzed root trait data (including 13 root traits) of the distal root branch order (first order roots) from 355 species covering six biomes.
We identified three major patterns: 1) root morphology varied markedly from tropical forests to grasslands and deserts with very coarse and very thin roots occurring simultaneously in tropical forests but only thin roots in temperate grasslands and deserts, possibly driven by shifting costs in root construction and patterns of resource supply in contrasting biomes; 2) root chemical traits displayed much smaller variation than morphological traits, and biome-level differences were statistically non-significant, possibly indicating stoichiometric homostasis in the metabolically most active root tissue (i.e., first order roots); 3) size-related root hydraulic traits showed very little variation with high degree of in overlap in traits values across biomes, suggesting conservatism in basic root hydraulic design. These findings provide insights into how distal absorptive roots are designed to facilitate the role of roots in overall plant functioning and plant adaptations in different biomes.