Jing Zhang

Plant roots and their mycorrhizal symbionts regulate soil organic carbon (SOC) dynamics in tropical forests, where succession‐driven shifts in mycorrhizal associations alter carbon allocation patterns. However, the relative contributions of roots versus extraradical mycorrhizal hyphae to SOC accumulation and decomposition across forest succession remain unclear. Using a 2‐year isotopic ingrowth‐core field experiment along a tropical forest chronosequence (70–400 years), we quantified the roles of roots and extraradical hyphae in new SOC accumulation and priming effects. After 2 years, roots contributed nearly four times more to SOC accumulation than hyphae across tropical forest succession. Roots enhanced new SOC accumulation while suppressing the positive priming effect on native SOC, leading to a net gain of 1.6 mg C g ⁻¹ soil yr. ⁻¹ , predominantly as particulate organic carbon. In contrast, extraradical hyphae had a marginal effect, contributing only 0.4 mg C g ⁻¹ soil yr. ⁻¹ . Root‐driven SOC input peaked in early succession, whereas hyphal contributions remained consistent. Our findings highlight the dominant role of roots—rather than mycorrhizal hyphae—in SOC accumulation and stabilization during tropical forest succession, emphasizing the need to incorporate root traits into management strategies to enhance SOC sequestration, particularly in tropical forests under increasing land‐use pressures.

Microbial metabolic products play a vital role in maintaining ecosystem multifunctionality, such as soil physical structure and soil organic carbon (SOC) preservation. Afforestation is an effective strategy to restore degraded land. Glomalin‐related soil proteins (GRSP) and amino sugars are regarded as stable microbial‐derived C, and their distribution within soil aggregates affects soil structure stability and SOC sequestration. However, the information about how afforestation affects the microbial contribution to SOC pools within aggregates is poorly understood. We assessed the accumulation and contribution of GRSP and amino sugars within soil aggregates along a restoration chronosequence (Bare land, Eucalyptus exserta plantation, native species mixed forest, and native forest) in tropical coastal terraces. Amino sugars and GRSP concentrations increased, whereas their contributions to the SOC pool decreased along the restoration chronosequence. Although microaggregates harbored greater microbial abundances, amino sugars and GRSP concentrations were not significantly affected by aggregate sizes. Interestingly, the contributions of amino sugars and GRSP to SOC pools decreased with decreasing aggregate size which might be associated with increased accumulation of plant‐derived C. However, the relative change rate of GRSP was consistently greater in all restoration chronosequences than that of amino sugars. The accumulation of GRSP and amino sugars in SOC pools was closely associated with the dynamics of soil fertility and the microbial community. Our findings suggest that GRSP accumulates faster and contributes more to SOC pools during restoration than amino sugars did which was greatly affected by aggregate sizes. Afforestation substantially enhanced soil quality with native forest comprising species sequestering more SOC than the monoculture plantation did. Such information is invaluable for improving our mechanistic understanding of microbial control over SOC preservation during degraded ecosystem restoration. Our findings also show that plantations using arbuscular mycorrhizal plants can be an effective practice to sequester more soil carbon during restoration.