The formation and persistence of soil organic matter has undergone a fundamental paradigm shift from a plant-centric view emphasizing lignin recalcitrance to a complementary microbial-centric framework. Quantitatively, meta-analyses demonstrate that microbial necromass contributes 51% of soil organic carbon in croplands and 47% in grasslands, but only 35% in forest topsoils, with fungal necromass exceeding bacterial necromass by a factor of 2.4–2.9 across ecosystems. However, critical evaluation reveals that this paradigm shift, while necessary, has introduced new uncertainties that are often obscured by the apparent precision of global necromass estimates. Three unresolved tensions are identified: (1) the "Quantification-Confidence Paradox"—where numerical precision in biomarker-based estimates masks fundamental uncertainty about conversion factors and the production-persistence distinction; (2) contradictory findings on nitrogen effects, mineral saturation, and the functional significance of death pathway chemistry that reveal mechanistic gaps in current understanding; and (3) the underappreciation of methodological biases that may systematically distort necromass contribution estimates across ecosystems. This review distinguishes itself from prior syntheses by adopting an explicitly critical stance: rather than cataloguing findings, the evidence quality is interrogated , contradictions are identified, and original interpretive frameworks are offered including the "Production-Persistence Decoupling" concept and a refined microbial carbon pump model incorporating a death pathway quality filter. The pathways of necromass production are systematically analyzed , competing hypotheses regarding stabilization mechanisms are critically assessed, and the relative importance of abiotic versus biotic controls is evaluated—distinguishing correlative patterns from demonstrated causal relationships. By integrating recent advances with explicit uncertainty assessment, a revised framework is presented that positions microbes as complementary architects of long-term carbon sequestration while identifying where current models fail and where empirical evidence remains insufficient. Critical research gaps are prioritized and the practical limitations of translating this paradigm into climate mitigation strategies are evaluated.
Hassan Etesami (Mon,) studied this question.