Since the 1980s, scientists have known fine roots (< 2 mm) are critical to ecosystem carbon cycling, with research long suggesting their contribution to soil carbon accrual may exceed that of aboveground plant parts like leaves. Yet more than 40 years later, a key knowledge gap remains: the role of multi-decadal root iterative dynamics (growth, turnover, decomposition) in soil carbon accumulation—especially for "absorptive roots," the finest, most metabolically active roots (typically the distal 2–3 root orders or < 0.5 mm in diameter).