Where and why do particulate organic matter (POM) and mineral-associated organic matter (MAOM) differ among diverse soils?
Where and why do particulate organic matter (POM) and mineral-associated organic matter (MAOM) differ among diverse soils?
复制标题
不同土壤中颗粒有机质 (POM) 和矿物质相关有机质 (MAOM) 在何处以及为何存在差异？
DOI：
10.1016/j.soilbio.2022.108756
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发表时间：
2022
影响因子：
9.7
通讯作者：
Hall, Steven J.
中科院分区：
文献类型：
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作者：
Yu, Wenjuan;Huang, Wenjuan;Weintraub-Leff, Samantha R.;Hall, Steven J.
土壤有机质（SOM）常被分为可操作的物理组分，如颗粒有机质（POM）和矿物相关有机质（MAOM），以提高我们对SOM持久性的理解。虽然人们普遍认为POM和MAOM具有不同的土壤地球化学特征，但POM和MAOM在其组成以及与非均质土壤中总SOM分解的关系方面存在差异的原因仍然没有得到解决。我们分析了元素，同位素和化学成分，包括漫反射红外傅立叶变换（DRIFT）光谱，POM和MAOM在156个土壤样品收集从20个国家生态观测网络（氖）网站跨越不同的生态系统（苔原到热带）在北美。我们使用了一种经典的尺寸分离方法，用于POM（53-2000 μm）和MAOM（<53 μm）的化学分散。不同土壤中POM和MAOM组分的C/N、δ 13 C和C-H（脂肪族）/C双键O的DRIFT谱具有相关性，且通常相似; C双键C（芳香族）/C双键O的DRIFT谱通常相似，但组分间不相关。一个流行的假设认为，MAOM是由微生物来源的OM占主导地位，但我们的研究结果表明，植物来源的OM也可以大大有助于MAOM，特别是在潮湿的森林接收>1200毫米的年降水量（MAOM C/N > 15）。多元统计分析表明，碳的数量和化学组成的MAOM可以有效地预测土壤碳分解在18个月的培养措施的POM。因此，POM和MAOM都可能在几个月的时间尺度上对分解有显著贡献，这可能是因为POM和MAOM的特性通常是相关的和/或MAOM的大池大小可以补偿其相对于POM的较低分解率。此外，我们发现，土壤地球化学组成（如粉砂和粘土，钙，可提取的铁和铝），沿着气候和生态系统类型，可以部分预测POM和MAOM的数量和组成的差异。总体而言，土壤中POM和MAOM之间的相对耦合与解耦是可预测的地球化学的基础上，这些相似性/差异提供了深入了解不同生态系统中MAOM的植物来源的变化。MAOM对短期土壤碳分解的重要性可能被低估了。
Soil organic matter (SOM) has often been separated into operational physical fractions, such as particulate organic matter (POM) and mineral-associated organic matter (MAOM), to improve our understanding of SOM persistence. While it is generally assumed that POM and MAOM have distinct biogeochemical characteristics, it remains unresolved where and why POM and MAOM differ in their composition and relationships to total SOM decomposition among heterogenous soils. We analyzed elemental, isotopic, and chemical composition, including diffuse reflectance infrared Fourier transform (DRIFT) spectra, of POM and MAOM in 156 soil samples collected from 20 National Ecological Observatory Network (NEON) sites spanning diverse ecosystems (tundra to tropics) across North America. We used a classic size separation method for POM (53–2000 μm) and MAOM (<53 μm) following chemical dispersion. Values of C/N, δ13C, and DRIFT spectra for C–H (aliphatic)/Cdouble bondO were correlated and often similar in POM and MAOM fractions across diverse soils; DRIFT spectra for Cdouble bondC (aromatic)/Cdouble bondO were often similar but uncorrelated between fractions. A prevalent hypothesis holds that MAOM is dominated by microbial-derived OM, yet our findings suggest that plant-derived OM can also contribute substantially to MAOM, especially in wet forests receiving >1200 mm annual precipitation (with MAOM C/N > 15). Multiple statistical analyses showed that C quantity and chemical composition of MAOM could as effectively predict soil C decomposition during an 18-month incubation as measures of POM. Thus, POM and MAOM both likely contributed significantly to decomposition over timescales of months, possibly because characteristics of POM and MAOM were often related and/or a large pool size of MAOM could compensate for its lower decomposition rate relative to POM. Further, we found that soil geochemical composition (such as silt and clay, calcium, oxalate-extractable iron and aluminum), along with climate and ecosystem type, could partly predict differences in quantity and composition between POM and MAOM. Overall, relative coupling vs. decoupling between POM and MAOM among soils was predictable based on geochemistry, and these similarities/differences provide insight into variation in the plant-derived sources of MAOM across diverse ecosystems. The importance of MAOM to short-term soil C decomposition has probably been underappreciated.