Aims <p>Non-structural carbohydrates (NSCs) can not only regulate various physiological activities but also reflect the carbon storage and availability of plants. However, the relationship between NSCs of absorptive roots and root economic space (RES) in woody plants, especially conifers and angiosperms, remains unclear. Moreover, how phylogeny and environment influence their relationships is unknown.</p> Methods <p>We measured NSCs (soluble sugars and starch) and economic functional root traits (root diameter, specific root length, root tissue density, and root N concentration) of absorptive roots across 56 woody species (including angiosperms and conifers) from five vegetation vertical zones along a 2000-m altitudinal gradient in Taibai Mountain.</p> Results <p>For angiosperms, the NSCs of absorptive roots were independent of RES and represented the defense gradient, which is negatively associated with RNC. The defense, collaboration, and conservation gradients in angiosperms were influenced by mean annual temperature (MAT), soil available nitrogen, and phylogeny, respectively, further causing the decoupling of NSCs and RES. Differently, for conifers, the NSCs of absorptive roots were closely related to the collaboration gradient dominated by root diameter and specific root length, which wasn’t influenced by environmental factors.</p> Conclusions <p>Our findings highlight distinct positions of NSCs in RES for conifers and angiosperms, shedding light on the different roles of NSCs in the two major extant clades of woody species. Future studies should validate these relationships across broader scales and a wider range of species, enhancing our ability to understand plant adaptation strategies from a physiological perspective.</p>