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  • 1.
    Fischer, Benjamin M. C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Aemisegger, Franziska
    Graf, Pascal
    Sodemann, Harald
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Zurich, Switzerland; Swedish University of Agricultural Sciences, Sweden.
    Assessing the Sampling Quality of a Low-Tech Low-Budget Volume-Based Rainfall Sampler for Stable Isotope Analysis2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id UNSP 244Article in journal (Refereed)
    Abstract [en]

    To better understand the small-scale variability of rainfall and its isotopic composition it is advantageous to utilize rain samplers which are at the same time low-cost, low-tech, robust, and precise with respect to the collected rainwater isotopic composition. We assessed whether a self-built version of the Kennedy sampler is able to collect rainwater consistently without mixing with antecedent collected water. We called the self-built sampler made from honey jars and silicon tubing the Zurich sequential sampler. Two laboratory experiments show that high rainfall intensities can be sampled and that the volume of water in a water sample originating from a different bottle was generally less than 1 ml. Rainwater was collected in 5 mm increments for stable isotope analysis using three (year 2011) and five (years 2015 and 2016) rain samplers in Zurich (Switzerland) during eleven rainfall events. The standard deviation of the total rainfall amounts between the different rain gauges was <1%. The standard deviation of delta O-18 and delta H-2 among the different sequential sampler bottles filled at the same time was generally <0.3 parts per thousand for delta O-18 and <2 parts per thousand for delta H-2 (8 out of 11 events). Larger standard deviations could be explained by leaking bottle(s) with subsequent mixing of water with different isotopic composition of at least one out of the five samplers. Our assessment shows that low-cost, low-tech rain samplers, when well maintained, can be used to collect sequential samples of rainfall for stable isotope analysis and are therefore suitable to study the spatio-temporal variability of the isotopic composition of rainfall.

  • 2.
    Fischer, Benjamin M. C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Frentress, Jay
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Greger, Maria
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, United States.
    Mojito, Anyone? An Exploration of Low-Tech Plant Water Extraction Methods for Isotopic Analysis Using Locally-Sourced Materials2019In: Frontiers in Earth Science, ISSN 2296-6463, Vol. 7, article id 150Article in journal (Refereed)
    Abstract [en]

    The stable isotope composition of water (delta O-18 and delta H-2) is an increasingly utilized tool to distinguish between different pools of water along the soil-plant-atmosphere continuum (SPAC) and thus provides information on how plants use water. Clear bottlenecks for the ubiquitous application of isotopic analysis across the SPAC are the relatively high-energy and specialized materials required to extract water from plant materials. Could simple and cost-effective do-it-yourself MacGyver methods be sufficient for extracting plant water for isotopic analysis? This study develops a suite of novel techniques for plant water extraction and compares them to a standard research-grade water extraction method. Our results show that low-tech methods using locally-sourced materials can indeed extract plant water consistently and comparably to what is done with other state-of-the-art methods. Further, our findings show that other factors play a larger role than water extraction methods in achieving the desired accuracy and precision of stable isotope composition: (1) appropriate transport, (2) fast sample processing and (3) efficient workflows. These results are methodologically promising for the rapid expansion of isotopic investigations, especially for citizen science and/or school projects or in remote areas, where improved SPAC understanding could help manage water resources to fulfill agricultural and other competing water needs.

  • 3.
    Fischer, Benjamin M. C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Morillas, Laura
    Garcia, Monica
    Johnson, Mark S.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Improving agricultural water use efficiency with biochar - A synthesis of biochar effects on water storage and fluxes across scales2019In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 657, p. 853-862Article in journal (Refereed)
    Abstract [en]

    There is an urgent need to develop agricultural methods that balance water supply and demand while at the same time improve resilience to climate variability. A promising instrument to address this need is biochar - a charcoal made from pyrolyzed organic material. However, it is often unclear how, if at all, biochar improves soil water availability, plant water consumption rates and crop yields. To address this question, we synthesized literature-derived observational data and evaluated the effects of biochar on evapotranspiration using a minimal soil water balance model. Results from the model were interpreted in the Budyko framework to assess how climatic conditions mediate the impacts of biochar on water fluxes. Our analysis of literature-derived observational data showed that while biochar addition generally increases the soil water holding capacity, it can have variable impacts on soil water retention relative to control conditions. Our modelling demonstrated that biochar increases long-term evapotranspiration rates, and therefore plant water availability, by increasing soil water retention capacity - especially in water-limited regions. Biochar amendments generally increased crop yields (75% of the compiled studies) and, in several cases (35% of the compiled studies), biochar amendments simultaneously increased crop yield and water use efficiencies. Hence, while biochar amendments are promising, the potential for variable impact highlights the need for targeted research on how biochar affects the soil-plant-water cycle.

  • 4. Floriancic, Marius G.
    et al.
    Fischer, Benjamin M. C.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Molnar, Peter
    Kirchner, James W.
    van Meerveld, Ilja H. J.
    Spatial variability in specific discharge and streamwater chemistry during low flows: Results from snapshot sampling campaigns in eleven Swiss catchments2019In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 33, no 22, p. 2847-2866Article in journal (Refereed)
    Abstract [en]

    Catchments consist of distinct landforms that affect the storage and release of subsurface water. Certain landforms may be the main contributors to streamflow during extended dry periods, and these may vary for different catchments in a given region. We present a unique dataset from snapshot field campaigns during low-flow conditions in 11 catchments across Switzerland to illustrate this. The catchments differed in size (10 to 110 km(2)), varied from predominantly agricultural lowlands to Alpine areas, and covered a range of physical characteristics. During each snapshot campaign, we jointly measured streamflow and collected water samples for the analysis of major ions and stable water isotopes. For every sampling location (basin), we determined several landscape characteristics from national geo-datasets, including drainage area, elevation, slope, flowpath length, dominant land use, and geological and geomorphological characteristics, such as the lithology and fraction of quaternary deposits. The results demonstrate very large spatial variability in specific low-flow discharge and water chemistry: Neighboring sampling locations could differ significantly in their specific discharge, isotopic composition, and ion concentrations, indicating that different sources contribute to streamflow during extended dry periods. However, none of the landscape characteristics that we analysed could explain the spatial variability in specific discharge or streamwater chemistry in multiple catchments. This suggests that local features determine the spatial differences in discharge and water chemistry during low-flow conditions and that this variability cannot be assessed a priori from available geodata and statistical relations to landscape characteristics. The results furthermore suggest that measurements at the catchment outlet during low-flow conditions do not reflect the heterogeneity of the different source areas in the catchment that contribute to streamflow.

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