Further experiments comparing direct vapor equilibration and cryogenic vacuum distillation for plant water stable isotope analysis

Millar, Cody; Pratt, Dyan; Schneider, David J.; Koehler, Geoff; McDonnell, Jeffrey J.

doi:10.1002/rcm.8530

Cited by 8 publications

(6 citation statements)

References 29 publications

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“…A further issue is the lack of comparability between the various types of extraction approaches. Extraction method intercomparisons utilizing soils spiked with waters of known isotope values, natural bulk soils, and plants grown in controlled and natural conditions showed significant differences in the isotopic values of analytes extracted by the tested methods (Barbeta et al, 2020; Kelln et al, 2001; Kübert et al, 2020; Mennekes et al, 2021; Millar et al, 2018, 2019; Orlowski et al, 2019; Orlowski, Pratt, & McDonnell, 2016; Zuecco et al, 2022). In the case of soils, the research found some extraction approaches were closer to their ‘truth value’ than others or that isotope values of extracted analytes were statistically different between methods.…”

Section: The Issuesmentioning

confidence: 99%

“…Beyond potential extraction induced errors (Chen et al, 2020;Fischer et al, 2019), we suggest that the greatest concern is the wide variety of extraction approaches being utilized and the lack of unified standard operating procedures (SOP) to guide their use (see Gralher et al, 2021;Orlowski et al, 2018). Research showed that significant differences were found in the isotopic composition of analytes extracted by various tested extraction methods (Barbeta et al, 2022;Kelln et al, 2001;Mennekes et al, 2021;Millar et al, 2018Millar et al, , 2019Orlowski et al, 2018;Orlowski, Pratt, & McDonnell, 2016;Zuecco et al, 2022). See Table 2 for extraction method error ranges.…”

Section: Step 3: Extraction Of Analytesmentioning

confidence: 99%

“…-3.41 (f), 1.2 (j), 0.33 (l) (f)Millar et al, 2018, (j) Millar et al, 2019, (l) Volkmann et al, 2016 Note: Method accuracy is shown as the SD of isotopic data in ‰ VSMOW. In some case a method error range is provided given the effects of different variables in the studies.…”

mentioning

confidence: 99%

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On the urgent need for standardization in isotope‐based ecohydrological investigations

Millar

Janzen

Nehemy

et al. 2022

Hydrological Processes

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Ecohydrological investigations commonly use the stable isotopes of water (hydrogen and oxygen) as conservative ecosystem tracers. This approach requires accessing and analysing water from plant and soil matrices. Generally, there are six steps involved to retrieve hydrogen and oxygen isotope values from these matrices: (1) sampling, (2) sample storage and transport, (3) extraction, (4) pre‐analysis processing, (5) isotopic analysis, and (6) post‐processing and correction. At each step, cumulative errors can be introduced which sum to non‐trivial magnitudes. These can impact subsequent interpretations about water cycling and partitioning through the soil–plant‐atmosphere continuum. At each of these steps, there are multiple possible options to select from resulting in tens of thousands of possible combinations used by researchers to go from plant and soil samples to isotopic data. In a newly emerging field, so many options can create interpretive confusion and major issues with data comparability. This points to the need for development of shared standardized approaches. Here we critically examine the state of the process chain, reflecting on the issues associated with each step, and provide suggestions to move our community towards standardization. Assessing this shared ‘process chain’ will help us see the problem in its entirety and facilitate community action towards agreed upon standardized approaches.

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Section: The Issuesmentioning

confidence: 99%

Section: Step 3: Extraction Of Analytesmentioning

confidence: 99%

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On the urgent need for standardization in isotope‐based ecohydrological investigations

Millar

Janzen

Nehemy

et al. 2022

Hydrological Processes

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“…CVD is the most widely used technique to obtain liquid water from plant and soil samples (Amin et al, 2020). CVD has been applied in many studies, compared across laboratories worldwide, and tested against other extraction methods (Millar et al, 2018(Millar et al, , 2019Orlowski et al, 2018;Orlowski, Pratt, et al, 2016). The protocol for CVD is described in detail in West et al (2006) and Orlowski et al (2013), but in short, the sample is placed in an extraction unit (e.g., Exetainer ® vial, glass unit) and connected (usually via stainless steel capillaries) to a collection unit (usually a glass-collection tube), where the extracted water is collected.…”

Section: Cryogenic Vacuum Distillationmentioning

confidence: 99%

Toward a common methodological framework for the sampling, extraction, and isotopic analysis of water in the Critical Zone to study vegetation water use

Ceperley,

Gimeno,

Jacobs

et al. 2024

WIREs Water

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The analysis of the stable isotopic composition of hydrogen and oxygen in water samples from soils and plants can help to identify sources of vegetation water uptake. This approach requires that the heterogeneous nature of plant and soil matrices is carefully accounted for during experimental design, sample collection, water extraction and analyses. The comparability and shortcomings of the different methods for extracting water and analyzing isotopic composition have been discussed in specialized literature. Yet, despite insightful comparisons of extraction methods and benchmarking methodologies of laboratories worldwide, the community still lacks a roadmap to guide sample collection, extraction, and isotopic analyses, and many practical issues for potential users remain unresolved: for example, which (soil or plant) water pool(s) does the extracted water represent? These constitute a hurdle for the implementation of the approach by newcomers. Here, we summarize discussions led in the framework of the COST Action WATSON (“WATer isotopeS in the critical zONe: from groundwater recharge to plant transpiration”—CA19120). We provide guidelines for (1) sampling soil and plant material for isotopic analysis, (2) methods for laboratory or in situ water extraction, and (3) measurements of isotopic composition. We highlight the importance of considering the process chain as a whole, from experimental design to isotopic analysis to minimize biased estimates of the relative contribution of different water sources to plant water uptake. We conclude by acknowledging some of the limitations of this methodology and advice on the collection of key environmental parameters prior to sample collection for isotopic analyses.This article is categorized under: Science of Water > Hydrological Processes Science of Water > Water and Environmental Change Science of Water > Water Extremes

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“…Recently, the use of cryogenic vacuum distillation techniques in hydrogen isotopic fractionation has been questioned as a possible cause of conflicting results in various studies (Chen et al, 2020). While some research supports this view (e.g., Millar et al, 2019), other studies provide evidence to the contrary (Allen & Kirchner, 2022;Amin et al, 2021;Evaristo et al, 2021;Newberry et al, 2017). Evaristo et al (2017) found that using both δ 2 H and δ 18 O in a Bayesian inference framework improved estimates of plant water sources.…”

Section: Limitations and Future Considerationsmentioning

confidence: 99%

Dynamic hydrological niche segregation: how plants compete for water in a semiarid ecosystem

Zhao¹,

Wang²,

Chun³

et al. 2023

Preprint

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Hydrological niche segregation (HNS), which refers to differences in root water uptake depth and physiological traits among coexisting species, remains poorly understood especially with respect to moisture changes and diverse water use strategies. This is particularly the case in regions with a seasonally dry climate where plants must constantly adapt to water stress. Over a 2-year period, we analyzed the isotopic compositions of xylem and soil water (δ2H, δ18O) and foliar δ13C to identify the water sources and intrinsic water use efficiency (WUEi), respectively, of four coexisting plant species. These species include Populus simonii (a type of tree), Caragana korshinskii and Salix psammophila (both types of shrub), and Artemisia ordosica (a semi-shrub). This study was conducted in a semi-arid ecosystem in China’s Loess Plateau (CLP). To quantify HNS defined by δ2H, δ18O and δ13C, we used a model called nicheROVER. Our results show that these four co-existing species had distinct position on a hydrological niche axis defined by their water sources and WUEi. P. simonii depended on deep soil water and demonstrated a high WUEi. Both shrubs, C. korshinskii and S. psammophila, utilized deep and intermediate soil water, respectively, and had comparable WUEi. The semi-shrub A. ordosica relied on shallow soil water and showed a low WUEi. These differences in water sources and WUEi led to HNS between A. ordosica and the other three species during the wet year. However, in a dry year, HNS reduced as the shrubs and semi-shrub increased their use of deep soil water and improved WUEi. Overall, these results demonstrate that HNS is a dynamic process that varies on at least an annual basis. It expands and contracts as plants regulate their water uptake and loss in response to changing soil moisture conditions.

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Further experiments comparing direct vapor equilibration and cryogenic vacuum distillation for plant water stable isotope analysis

Cited by 8 publications

References 29 publications

On the urgent need for standardization in isotope‐based ecohydrological investigations

On the urgent need for standardization in isotope‐based ecohydrological investigations

Toward a common methodological framework for the sampling, extraction, and isotopic analysis of water in the Critical Zone to study vegetation water use

Dynamic hydrological niche segregation: how plants compete for water in a semiarid ecosystem

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