In situ measurements of soil and vadose zone water isotopes reveal water storage and fluxes in semi-aird ecosystems

These data are from the following publication:
Oerter, E. J., & Bowen, G. (2017). In situ monitoring of H and O stable isotopes in soil water reveals ecohydrologic dynamics in managed soil systems. Ecohydrology, 10(4).

Abstract:

The water cycle in urban and hydrologically-managed settings is subject to perturbations that are dynamic on small spatial and temporal scales, the effects of which may be especially profound in soils. We deploy a membrane inlet-based laser spectroscopy system in conjunction with soil moisture sensors to monitor soil water dynamics and H and O stable isotope ratios (δ H and δ18O values) in a seasonally irrigated urban landscaped garden soil over the course of 9 months between the cessation of irrigation in the autumn and the onset of irrigation through the summer. We find that soil water δ2H and δ18O values predominately reflect seasonal precipitation and irrigation inputs. A comparison of total soil water by cryogenic extraction and mobile soil water measured by in situ water vapor probes, reveals that initial infiltration events after long periods of soil drying (the autumn season in this case) emplace water into the soil matrix that is not easily replaced by, or mixed with, successive pulses of infiltrating soil water. Tree stem xylem water H and O stable isotope composition did not match that of available water sources. These findings suggest that partitioning of soil water into mobile and immobile “pools” and resulting ecohydrologic separation may occur in engineered and hydrologically-managed soils and not be limited to natural settings. The laser spectroscopy method detailed here has potential to yield insights in a variety of Critical Zone and vadose zone studies, potential that is heightened by the simplicity and portability of the system.

本数据集源自以下出版物：

Oerter, E. J., & Bowen, G. (2017). 基于现场监测土壤水中氢和氧稳定同位素，揭示管理土壤系统中的生态水文学动力学。Ecohydrology, 10(4).

摘要：

在城市和水利工程管理环境下，水循环受到动态变化的影响，这种变化在小尺度的空间和时间范围内尤为显著，其影响在土壤中可能尤为深远。本研究采用基于膜进气激光光谱系统结合土壤湿度传感器，对秋季停止灌溉至夏季开始灌溉期间，为期9个月的季节性灌溉城市景观花园土壤中的土壤水动力学和氢、氧稳定同位素比值（δ2H 和 δ18O 值）进行监测。研究发现，土壤水 δ2H 和 δ18O 值主要反映了季节性降水和灌溉输入。通过低温提取的总土壤水与现场水汽探头测量的移动土壤水进行比较，发现长期土壤干燥（在本例中为秋季）后的初次入渗事件将水引入土壤基质，这种水不易被后续入渗的土壤水替代或混合。树木茎干木质部水的氢和氧稳定同位素组成与可用水源不匹配。这些发现表明，在工程和水利工程管理的土壤中，土壤水分可能分为移动和固定‘池’，并导致生态水文学分离，而这种分离并非仅限于自然设置。本文详细描述的激光光谱方法有望在多种关键带和包气带研究中提供见解，其潜力因系统的简便性和便携性而得到提升。