A stoichiometric approach to estimate sources of mineral-associated soil organic matter
A stoichiometric approach to estimate sources of mineral-associated soil organic matter
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DOI：
10.1111/gcb.17092
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发表时间：
2024-01-01
影响因子：
11.6
通讯作者：
Ding，Fan
中科院分区：
文献类型：
--
作者：
Chang，Yi;Sokol，Noah W.;Ding，Fan
与矿物质相关的土壤有机质（MAOM）是陆地生物圈中最大、最慢循环的碳（C）库。 MAOM 主要来源于植物和微生物来源，但这两种来源对 MAOM 的相对贡献仍未确定。解决这个问题对于管理和模拟土壤碳对环境变化的响应至关重要。微生物生物标志物，特别是氨基糖，是用于估计微生物与植物对 MAOM 贡献的主要方法，尽管这些估计存在系统偏差。显然需要独立的证据来帮助确定植物与微生物对 MAOM 贡献的相对重要性。在这里，我们合成了森林、草原和农田土壤中 MAOM、颗粒有机物 (POM) 和微生物生物量的 288 个 C/N 比数据集。微生物生物质是形成 MAOM 的微生物残留物的来源，而 POM 池是形成 MAOM 的植物残留物的直接前体。然后，我们使用基于双池同位素混合模型的化学计量方法来估计植物残留物 (POM) 与微生物来源对 MAOM 池的比例贡献。根据我们方法所依据的假设，微生物输入占 MAOM 池的 34% 至 47%，而植物残留物占 53%–66%。因此，我们的结果挑战了现有的假设，即微生物贡献是 MAOM 的主要成分。我们的结论是，生物地球化学理论和模型应该解释 MAOM 形成的多种途径，并且需要多个独立的证据来解决植物与微生物在 MAOM 形成中占主导地位的时间和地点。
Mineral‐associated soil organic matter (MAOM) is the largest, slowest cycling pool of carbon (C) in the terrestrial biosphere. MAOM is primarily derived from plant and microbial sources, yet the relative contributions of these two sources to MAOM remain unresolved. Resolving this issue is essential for managing and modeling soil carbon responses to environmental change. Microbial biomarkers, particularly amino sugars, are the primary method used to estimate microbial versus plant contributions to MAOM, despite systematic biases associated with these estimates. There is a clear need for independent lines of evidence to help determine the relative importance of plant versus microbial contributions to MAOM. Here, we synthesized 288 datasets of C/N ratios for MAOM, particulate organic matter (POM), and microbial biomass across the soils of forests, grasslands, and croplands. Microbial biomass is the source of microbial residues that form MAOM, whereas the POM pool is the direct precursor of plant residues that form MAOM. We then used a stoichiometric approach—based on two‐pool, isotope‐mixing models—to estimate the proportional contribution of plant residue (POM) versus microbial sources to the MAOM pool. Depending on the assumptions underlying our approach, microbial inputs accounted for between 34% and 47% of the MAOM pool, whereas plant residues contributed 53%–66%. Our results therefore challenge the existing hypothesis that microbial contributions are the dominant constituents of MAOM. We conclude that biogeochemical theory and models should account for multiple pathways of MAOM formation, and that multiple independent lines of evidence are required to resolve where and when plant versus microbial contributions are dominant in MAOM formation.