Abstract Detailed knowledge of soil moisture (θ) is crucial for implementing appropriate soil and crop management decisions and assuring crop productivity and soil functioning. θ measurement is challenging in the stony soils of traditional olive orchards where the operationality of common sensors is often compromised and fine scale variability of soil properties is complex as a result of the presence and specific architecture of the tree root system and canopy. In such environments, non-invasive electromagnetic induction (EMI) sensors constitute an alternative for measuring θ. Here we evaluate this alternative by exploring relationships between θ and apparent electrical conductivity (ECa) and contribute to improved understanding of spatio-temporal θ variability in the proximity of olive trees. Continuously measured θ in a trench on one side of an olive tree was complemented with 47 ECa surveys conducted periodically at the opposite side of the tree during a period of 15 months. θ was measured in the trench at five distances from the trunk (0.6–3.8 m) and at five depths (0.1–0.8 m). ECa was measured at the same distances from the trunk. We observed similar temporal patterns of θ and ECa in response to precipitation and evaporation at the site. The proportionality between spatial means of θ and ECa and the similarity in the relationships between spatial mean and standard deviation for each variable revealed concurrent spatio-temporal patterns. Dependence on distance to the trunk was different for θ and ECa, with an apparent erratic response for the former and a positive relationship for the latter. The slope of the linear θ-ECa models showed power law decay with distance to the trunk as a result of the varying soil and tree properties around the tree. These results pave the way for implementing coupled static-mobile ECa monitoring systems and θ estimation in olive orchards from the plot to the field and farm scales.

中文翻译：

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橄榄树附近土壤水分和表观电导率的同时变化

摘要 土壤水分 (θ) 的详细知识对于实施适当的土壤和作物管理决策以及确保作物生产力和土壤功能至关重要。θ 测量在传统橄榄园的石质土壤中具有挑战性，因为树根系统和冠层的存在和特定结构，常见传感器的可操作性通常会受到影响，并且土壤特性的精细尺度变化很复杂。在这种环境中，非侵入式电磁感应 (EMI) 传感器构成了测量 θ 的替代方案。在这里，我们通过探索 θ 与表观电导率 (ECa) 之间的关系来评估这种替代方法，并有助于提高对橄榄树附近时空 θ 变异性的理解。在 15 个月的时间里，在橄榄树一侧的沟渠中连续测量 θ，并辅以在橄榄树另一侧定期进行的 47 次 ECa 调查。θ 是在距树干五个距离（0.6-3.8 m）和五个深度（0.1-0.8 m）的沟槽中测量的。在距躯干相同距离处测量 ECa。我们观察到相似的 θ 和 ECa 时间模式响应现场的降水和蒸发。θ 和 ECa 的空间平均值之间的比例以及每个变量的空间平均值和标准偏差之间关系的相似性揭示了并发的时空模式。θ 和 ECa 对躯干距离的依赖性不同，前者明显不稳定，后者呈正相关。由于树木周围土壤和树木特性的变化，线性 θ-ECa 模型的斜率显示幂律随到树干的距离而衰减。这些结果为在橄榄园从地块到田间和农场规模实施耦合静态-移动 ECa 监测系统和 θ 估计铺平了道路。