Increasing soil organic carbon (SOC) concentration is a desirable aspect of afforestation. Glomalin-related soil protein (GRSP) is a ubiquitous component of SOC, preferentially produced by arbuscular mycorrhizal fungi (AMF) during symbiotic association with the plant roots. Although the role of AMF in GRSP production is well established, the role of root in GRSP production is not yet clear. Hence, we aimed to assess the glomalin in different tree roots (i.e., glomalin-related root protein; GRRP) and its influence on GRSP and SOC storage in trees’ rhizosphere and interspace. The experiment was conducted in a tropical dry forest with six native trees (Hardwickia binata, Lagerstroemia parviflora, Diospyros melanoxylon, Terminalia tomentosa, Shorea robusta, and Anogeissus latifolia) and a planted Teak (Tectona grandis). The fine roots (from the rhizosphere) and topsoils (0–15 cm) were collected from the rhizosphere and interspace of each tree. We found GRRP concentration varying between trees, with higher values observed in the roots of native trees than those of Teak. The AMF colonization was positively correlated with GRRP (r² = 0.88), and GRRP positively correlated with GRSP and SOC. The higher correlation of GRRP was observed with GRSP (r² = 0.70–0.79) compared with SOC (r² = 0.56–0.58), while the correlation was much stronger between GRSP and SOC (r² = 0.91). These results indicate that GRRP influences SOC storage via mediating GRSP concentration. We suggest that GRRP can be used as an indicator for species screening during afforestation with the aim to improve SOC storage on an afforested landscape.