Despite the recognized importance of the contribution of microbial necromass to soil organic carbon (SOC) sequestration, at a global scale, there has been no quantification for cropland, grassland, and forest ecosystems. To address this knowledge gap, the contents of fungal and bacterial necromass were estimated based on glucosamine and muramic acid contents in cropland (986 samples), grassland (278 samples), and forest (452 samples) soils. On an average, microbial necromass C contributed 51%, 47%, and 35% to the SOC in cropland, grassland, and forest soils, respectively, in the first 20 cm of topsoil. The contribution of microbial necromass to SOC increased with soil depth in grasslands (from 47% to 54%) and forests (from 34% to 44%), while it decreased in croplands (from 51% to 24%). The microbial necromass accumulation coefficient (the ratio between necromass and living microbial biomass C) was higher in soil from croplands (41) and grasslands (33) than in forest (20) soils. These results suggest that the turnover of living microbial biomass is faster in grassland and cropland soils than in forest soils, where the latter contains more partially decomposed plant residues. Fungal necromass C (>65% of total necromass) had consistently higher contributions to SOC than bacterial necromass C (32–36%) in all soils due to i) a larger living fungal biomass than bacterial biomass, and ii) fungal cell compounds being decomposed slowly and, thus able to persist longer in soil. The ratio of fungal:bacterial necromass C increased from 2.4 to 2.9 in the order of croplands < grasslands < forests, because fungi are the principal decomposers of complex substrates dominant in grassland and, especially, in forest soils. The ratios of bacterial:microbial necromass and bacterial:fungal necromass in cropland soils are larger than those in grassland and forest soils. This result indicates that the relative contribution of fungal necromass to total microbial necromass is lowest in cropland among the three land uses. Moreover, fungal and bacterial necromass increased with the total living microbial C and N contents. Lower temperatures and soil pH (e.g., in temperate and boreal ecosystems) stimulate fungal and bacterial necromass accumulation. These findings highlight the fact that shifts in the bacterial:fungal necromass ratio and the microbial necromass contribution to SOC are ecosystem-specific and depend on climate. In conclusion, microbial necromass contributes to approximately half of the SOC in cropland and grassland soils, and only 35% in forest soils; whereas, two-thirds of microbial necromass are of fungal origin.

尽管微生物死尸对土壤有机碳 (SOC) 封存的贡献已得到公认，但在全球范围内，尚未对农田、草地和森林生态系统进行量化。为了解决这一知识差距，根据农田（986 个样本）、草地（278 个样本）和森林（452 个样本）土壤中的葡萄糖胺和胞壁酸含量估算了真菌和细菌死灵菌的含量。平均而言，在前 20 厘米表层土壤中，微生物死生物 C 分别对农田、草地和森林土壤中的 SOC 贡献了 51%、47% 和 35%。在草地（从 47% 到 54%）和森林（从 34% 到 44%）中，微生物死尸对 SOC 的贡献随着土壤深度的增加而增加，而在农田（从 51% 到 24%）中则下降。来自农田 (41) 和草地 (33) 的土壤中的微生物死尸积累系数 (死尸与活微生物生物量 C 之间的比率) 高于森林 (20) 土壤中的土壤。这些结果表明，草地和农田土壤中活微生物生物量的周转速度快于森林土壤，后者含有更多部分分解的植物残留物。由于 i) 比细菌生物量更大的活真菌生物量，以及 ii) 真菌细胞化合物是分解缓慢，因此能够在土壤中持续更长时间。真菌：细菌死生物C的比例从2.4增加到2.9，顺序为农田<草地<森林，因为真菌是草原，尤其是森林土壤中占主导地位的复杂基质的主要分解者。农田土壤中细菌:微生物菌体和细菌:真菌菌体的比例大于草地和森林土壤。该结果表明，在三种土地利用方式中，农田中真菌坏死对总微生物坏死的相对贡献最低。此外，真菌和细菌坏死物随着活微生物 C 和 N 总含量的增加而增加。较低的温度和土壤 pH 值（例如，在温带和寒带生态系统中）会刺激真菌和细菌死尸的积累。这些发现强调了一个事实，即细菌：真菌死尸比的变化和微生物死尸对 SOC 的贡献是特定于生态系统的，并取决于气候。综上所述，在农田和草地土壤中，微生物死尸约占 SOC 的一半，在森林土壤中仅占 35%；而三分之二的微生物坏死是真菌来源的。