Accurate determination of the water retention curve (WRC) of a soil is essential for the understanding and modelling of the subsurface hydrological, ecological, and biogeochemical processes. Volcanic ash soils with andic properties (Andosols) are recognized as important providers of ecological and hydrological services in mountainous regions worldwide due to their large fraction of small size particles (clay, silt, and organic matter) that gives them an outstanding water holding capacity. Previous comparative analyses of in situ (field) and standard laboratory methods for the determination of the WRC of Andosols showed contrasting results. Based on an extensive analysis of laboratory, experimental, and field measured WRCs of Andosols in combination with data extracted from the published literature we show that standard laboratory methods using small soil sample volumes (≤300 cm³) mimic the WRC of these soils only partially. The results obtained by the latter resemble only a small portion of the wet range of the Andosols' WRC (from saturation up to −5 kPa, or pF 1.7), but overestimate substantially their water content for higher matric potentials. This discrepancy occurs irrespective of site‐specific land use and cover, soil properties, and applied method. The disagreement limits our capacity to infer correctly subsurface hydrological behaviour, as illustrated through the analysis of long‐term soil moisture and matric potential data from an experimental site in the tropical Andes. These findings imply that results reported in past research should be used with caution and that future research should focus on determining laboratory methods that allow obtaining a correct characterization of the WRC of Andosols. For the latter, a set of recommendations and future directions to solve the identified methodological issues is proposed.

中文翻译：

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现场，实验室和文献回顾了火山灰土壤保水曲线的评估：标准实验室方法如何很好地反映田间条件？

准确确定土壤的保水曲线（WRC）对于理解和模拟地下水文，生态和生物地球化学过程至关重要。具有火山灰质的火山灰土壤（Andosols）因其大部分小颗粒（粘土，淤泥和有机物）而具有出色的保水能力，因此被公认为是世界范围内山区生态和水文服务的重要提供者。先前对原位（田间）和标准实验室方法进行的Andosols WRC测定的比较分析显示出相反的结果。基于对实验室，实验，³）仅部分模拟这些土壤的WRC。后者获得的结果仅与Andosols WRC的湿润范围的一小部分相似（从饱和到-5 kPa或pF 1.7），但是对于较高的基质电势，它们高估了其水分含量。不论具体地点的土地使用和覆盖，土壤性质和应用方法如何，都会出现这种差异。分歧限制了我们正确推断地下水文行为的能力，这通过对热带安第斯山脉一个实验点的长期土壤水分和基质势数据的分析得以说明。这些发现表明，应谨慎使用过去研究中报告的结果，而未来研究应着重于确定能够正确鉴定Andosols WRC的实验室方法。