Plants have evolved root traits that ensure water and nutrient acquisition balanced by the carbon acquired in habitats ranging from wet tropical forests to dry deserts. While data on plant aboveground traits have been extensively documented and have yielded many global-scale patterns, the understanding of root structure and function across species and biomes remain rudimentary. In particular, the lack of information on the biogeography of roots has prevented the incorporation of strategies of belowground resource acquisition across different biomes into a conceptual framework useful for global models of carbon, nitrogen and water cycles. Here, we used root trait data of first-order roots (the most distal and metabolically active roots in the fine root system) from 369 species across seven biomes to explore the coordination of root traits associated with root form and function across biomes and plant functional groups.
Results/Conclusions
We showed that the diversity of root form (indicated by the species-specific variation of morphological traits) is highest in tropical and subtropical forests where many ancestral phylogenetic groups are preserved, but declines rapidly from tropics to temperate to desert biomes, possibly driven by selection pressure of water availability. However，the linkage of root construction with longevity was weak, due to lacking protective tissues in such high efficient, plastic, and tiny absorptive roots. Colonization by mycorrhizal fungi in roots allowed the degree of economics spectrum for the two root fungal modular to be more flexibly and complementarily regulated than leaves. Global root traits biogeography patterns are difficult to predict the nitrogen acquisition rates, because the acquisition rate together with nitrogen concentrations lacked significantly biome-level differences and instead showed global physiological convergence.
These findings shed new light on how roots adapted to different environments and how root biogeography can contribute to the understanding of the whole-plant ecological strategies and nutrients foraging behaviors across habitats, thus facilitating the incorporation of belowground traits in global spectrum of plant form and function as well as biogeochemical modeling.