Recent studies indicate that climate change influences soil mineralogy by altering weathering processes and thus impacts soil aggregation and organic carbon (SOC) stability. Alpine ecosystems of the Neotropical Andes are characterized by high SOC stocks, which are important for sustaining ecosystem services. However, climate change in the form of altered precipitation patterns can potentially affect soil aggregation and SOC stability with potentially significant effects on the soil's ecosystem services. This study aimed to investigate the effects of precipitation and lithology on soil aggregation and SOC stability in the Peruvian Andean grasslands, and it assessed whether occlusion of organic matter (OM) in aggregates controls SOC stability. For this, samples were collected from soils on limestone and soils on acid igneous rocks from two sites with contrasting precipitation levels. We used a dry-sieving method to quantify aggregate-size distribution and applied a 76 d soil incubation with intact and crushed aggregates to investigate SOC stability's dependence on aggregation. SOC stocks ranged from 153±27 to 405±42 Mg ha⁻¹, and the highest stocks were found in the limestone soils of the wet site. We found lithology rather than precipitation to be the key factor regulating soil aggregate-size distribution, as indicated by coarse aggregates in the limestone soils and fine aggregates in the acid igneous rock soils. SOC stability estimated by specific SOC mineralization rates decreased with precipitation in the limestone soils, but only minor differences were found between wet and dry sites in the acid igneous rock soils. Aggregate destruction had a limited effect on SOC mineralization, which indicates that occlusion of OM in aggregates played a minor role in OM stabilization. This was further supported by the inconsistent patterns of aggregate-size distribution compared to the patterns of SOC stability. We propose that OM adsorption on mineral surfaces is the main OM stabilization mechanism controlling SOC stocks and stability. The results highlight the interactions between precipitation and lithology on SOC stability, which are likely controlled by soil mineralogy in relation to OM input.

中文翻译：

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岩石和气候控制的秘鲁安第斯山脉土壤总量分布和有机碳稳定性

最近的研究表明，气候变化通过改变风化过程影响土壤矿物学，从而影响土壤聚集和有机碳（SOC）稳定性。新热带安第斯山脉的高山生态系统的特点是SOC含量高，这对于维持生态系统服务很重要。但是，以变化的降水模式形式出现的气候变化可能会影响土壤聚集和SOC稳定性，并对土壤生态系统服务产生重大影响。这项研究旨在调查降水和岩性对秘鲁安第斯草原上土壤聚集和SOC稳定性的影响，并评估聚集物中有机物（OM）的吸附是否控制SOC的稳定性。为了这，从两个地点的石灰石和酸性火成岩的土壤中采集了两个样品，且降水水平相反。我们使用干筛法来量化骨料粒度分布，并应用了76 d将土壤与完整的碎料一起培养，以研究SOC稳定性对聚集体的依赖性。SOC储量范围为153±27至405±42  Mg ha ^-1，并且在湿地的石灰岩土壤中存量最高。我们发现，岩性而不是降水是调节土壤骨料粒径分布的关键因素，正如石灰岩土壤中的粗骨料和酸性火成岩土壤中的细骨料所表明的那样。通过特定的SOC矿化速率估算的SOC稳定性随石灰岩土壤中的降水量而降低，但在酸性火成岩土壤中的干湿点之间只有很小的差异。骨料破坏对SOC矿化的影响有限，这表明骨料中OM的阻塞在OM稳定中起较小作用。与SOC稳定模式相比，聚合体大小分布的模式不一致也进一步支持了这一点。我们认为，矿物表面上的OM吸附是控制SOC存量和稳定性的主要OM稳定机制。结果突出了降水和岩性之间在SOC稳定性上的相互作用，这很可能受土壤矿物学与OM输入有关的控制。