Hydraulic redistribution (HR) can buffer drought events of tree individuals, however, its relevance for neighbouring trees remains unclear. Here, we quantified HR to neighbouring trees in single‐ and ...mixed‐species combinations. We hypothesized that uptake of HR water positively correlates with root length, number of root tips and root xylem hydraulic conductivity and that neighbours in single‐species combinations receive more HR water than in phylogenetic distant mixed‐species combinations. In a split‐root experiment, a sapling with its roots split between two pots redistributed deuterium labelled water from a moist to a dry pot with an additional tree each. We quantified HR water received by the sapling in the dry pot for six temperate tree species. After 7 days, one quarter of the water in roots (2.1 ± 0.4 ml), stems (0.8 ± 0.2 ml) and transpiration (1.0 ± 0.3 ml) of the drought stressed sapling originated from HR. The amount of HR water transpired by the receiving plant stayed constant throughout the experiment. While the uptake of HR water increased with root length, species identity did not affect HR as saplings of Picea abies ((L.) Karst) and Fagus sylvatica (L.) in single‐ and mixed‐species combinations received the same amount of HR water.
We quantified hydraulically redistributed water towards neighbouring saplings of six temperate tree species. One quarter of the water found in roots, shoots and transpiration originated from HR, with no differences due to species mixture, emphasizing the major importance of HR for temperate trees.
Understanding interactions between surface water (SW) and groundwater (GW) is challenging because of the lack of information available and the complexity of the processes involved. In this paper, ...SW-GW interactions are simulated using numerical modelling integrated with insights from water isotopes. Isotope analysis can be used to (i) determine the relative contribution from different sources of water into aquifer recharge and (ii) identify areas with high SW-GW interactions. The results, for the Shiraz catchment in Iran, show that (i) SWAT-MODFLOW has better performance than stand-alone SWAT (R2 improvement from 0.50 to 0.54) and (ii) SWAT-MODFLOW calibrated with insights from isotope data (SWAT-MODFLOW-ISO) has significantly better performance than SWAT-MODFLOW (R2 improvement from 0.54 to 0.68 and RMSE reduction from 1.67 to 1.33). This demonstrates that insights into SW-GW interactions that are revealed by isotopes can be used to improve hydrological modelling performance.
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•Improve SW-GW interaction simulation by incorporating insights from water isotopes.•Tests how realistic numerical methods are when simulating SW-GW interactions.•Couple insights from water isotopes with SWAT-MODFLOW to improve SW-GW modelling.
In order to enhance hydrogen-water isotope exchange performance, a hydrophobic microenvironment was constructed within the catalyst support and a bimetal catalyst was loaded. The catalyst was ...superhydrophobic, resulting in a significant improvement in performance. Through the adsorption/desorption performance test of water vapor, it was observed that the hydrophobic microenvironment could increase the diffusion rate of the reactant, while metal doping modification could enhance the concentration of the reactant around the active center. Comparatively, the catalytic performance of the catalyst containing the hydrophobic microenvironment was superior to that of the normal hydrophobic catalysts, even when the hydrophobicity was slightly diminished.
•Hydrophobic catalyst with hydrophobic microenvironment was synthesized through chemical modification.•The hydrophobic microenvironment enhanced the diffusion rate of water vapor.•Bimetallic enhanced the adsorption of water vapor.•The high performance and stability of the catalyst indicate its potential for tritium water treatment.
•The far-infrared rotational spectrum of water vapour enriched in 18O is studied by FTS with a synchrotron radiation source.•Lines of about 2570 transitions of seven water isotopologues are observed ...and assigned for the first time.•142 new empirical energy levels are determined for H218O, H217O, HD18O, and HD17O.•Significant deviations are noted compared to HITRAN2016 line positions and to the energy levels recommended by an IUPAC-task group.
The rotational spectrum of water vapour highly enriched in 18O has been studied by high resolution (≈ 0.001 cm−1) Fourier transform spectroscopy at the AILES beam line of the SOLEIL synchrotron. The room temperature absorption spectrum has been recorded between 40 and 700 cm−1. The 18O enrichment of the sample was about 97% while the gas pressure and the absorption pathlength were set to 0.97 mbar and 151.75 m, respectively. The spectrum contains more than 4800 rotational transitions from seven water isotopologues (H218O, H216O, H217O, HD18O, HD16O, HD17O, D218O). The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Schwenke and Partridge. The amount and accuracy of the reported line positions represent an important extension compared to previous works. Overall, lines of about 2570 transitions are observed for the first time and 35, 41, 50, and 16 new energy levels are determined for H218O, H217O, HD18O, and HD17O, respectively. The set of derived energy levels shows a number of important differences from those recommended by an IUPAC-task group. Compared to the HITRAN2016 database, numerous deviations of line positions (up to 0.15 cm−1) are found for the H217O, H218O, HD17O, and HD18O species. Incomplete and wrong HITRAN's assignments of more than 90 transitions for H218O, H217O and HD18O are identified. Overall, the measured line positions will allow to significantly refine and complete the sets of empirical energy levels of H218O, H217O, HD18O and HD17O in the ground vibrational state.
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Hydraulic redistribution (HR) of soil water through plant roots is widely described; however its extent, especially in temperate trees, remains unclear. Here, we quantified HR of five temperate tree ...species. We hypothesized that both, HR within a plant and into the soil increase with higher water‐potential gradients, larger root conduit diameters and root‐xylem hydraulic conductivities as HR driving factors.
Saplings of conifer (Picea abies, Pseudotsuga menziesii), diffuse‐porous (Acer pseudoplatanus) and ring‐porous species (Castanea sativa, Quercus robur) were planted in split‐root systems, where one plant had its roots split between two pots with different water‐potential gradients (0.23–4.20 MPa). We quantified HR via deuterium labelling.
Species redistributed 0.39 ± 0.14 ml of water overnight (0.08 ± 0.01 ml/g root mass). Higher pre‐dawn water‐potential gradients, hydraulic conductivities and larger conduits significantly increased HR quantity. Hydraulic conductivity was the most important driving factor on HR amounts, within the plants (0.03 ± 0.01 ml/g) and into the soil (0.06 ± 0.01 ml/g).
Additional factors as soil‐root contact should be considered, especially when calculating water transfer into the soil. Nevertheless, trees maintaining high‐xylem hydraulic conductivity showed higher HR amounts, potentially making them valuable ‘silvicultural tools’ to improve plant water status.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
Partitioning of evapotranspiration (ET) in urban forest lands plays a vital role in mitigating ambient temperature and evaluating the effects of urbanization on the urban hydrological cycle. While ET ...partitioning has been extensively studied in diverse natural ecosystems, there remains a significant paucity of research on urban ecosystems. The flux variance similarity (FVS) theory is used to partition urban forest ET into soil evaporation (E) and vegetation transpiration (T). This involves measurements from eddy covariance of water vapor and carbon dioxide fluxes, along with an estimated leaf-level water use efficiency (WUE) algorithm. The study compares five WUE algorithms in partitioning the average transpiration fraction (T/ET) and validates the results using two years of oxygen isotope observations. Although all five FVS-based WUE algorithms effectively capture the dynamic changes in hourly scale T and E across the four seasons, the algorithm that assumes a constant ratio of intercellular CO2 concentration (ci) to ambient CO2 concentration (ca) provides the most accurate simulation results for the ratio of T/ET. The performance metrics for this specific algorithm include the RMSE of 0.06, R2 of 0.88, the bias of 0.02, and MAPE of 8.9 %, respectively. Comparing urban forests to natural forests, the T/ET in urban areas is approximately 2.4–25.3 % higher, possibly due to the elevated air temperature (Ta), greater leaf area index (LAI), and increased soil water availability. Correlation analysis reveals that the T/ET dynamic is primarily controlled by Ta, LAI, net radiation, ca, and soil water content at half-hourly, daily, and monthly scales. This research provides valuable insights into the performance and applicability of various WUE algorithms in urban forests, contributing significantly to understanding the impact of urbanization on energy, water, and carbon cycles within ecosystems.
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•The flux variance similarity theory was used to partition urban forest ET.•The T/ET ratio was verified using two years of δ18O isotope observations.•The performance of five WUE algorithms in ET partitioning was intercompared.•The best ET partition accuracy was yielded by estimating WUE with the ci/ca ratio.•The urban forest T/ET is higher than natural ecosystems.
Stable isotopes of water are ideal tracers to integrate into process‐based models, advancing ecohydrological understanding. Current tracer‐aided ecohydrological modeling is mostly conducted in ...relatively small‐scale catchments, due to limited tracer data availability and often highly damped stream isotope signals in larger catchments (>100 km2). Recent model developments have prioritized better spatial representation, offering new potential for advancing upscaling in tracer‐aided modeling. Here, we adapted the fully distributed EcH2O‐iso model to the Selke catchment (456 km2, Germany), incorporating monthly sampled isotopes from seven sites between 2012 and 2017. Parameter sensitivity analysis indicated that the information content of isotope data was generally complementary to discharge and more sensitive to runoff partitioning, soil water and energy dynamics. Multi‐criteria calibrations revealed that inclusion of isotopes could significantly improve discharge performance during validations and isotope simulations, resulting in more reasonable estimates of the seasonality of stream water ages. However, capturing isotopic signals of highly non‐linear near‐surface processes remained challenging for the upscaled model, but still allowed for plausible simulation of water ages reflecting non‐stationarity in transport and mixing. The detailed modeling also helped unravel spatio‐temporally varying patterns of water storage‐flux‐age interactions and their interplay under severe drought conditions. Embracing the upscaling challenges, this study demonstrated that even coarsely sampled isotope data can be of value in aiding ecohydrological modeling and consequent process representation in larger catchments. The derived innovative insights into ecohydrological functioning at scales commensurate with management decision making, are of particular importance for guiding science‐based measures for tackling environmental changes.
Key Points
Process‐based tracer‐aided ecohydrological modeling is upscaled to >100 km2 catchments using stable water isotopes
Isotopes benefit large‐scale modeling in substantially improving model robustness and reliability of water age estimates
Larger‐scale water partitioning and drought responses are controlled by heterogeneity in catchment organization
•Nutrient management practices impacted the magnitude of incidental nutrient loss.•Nitrate-N concentration was similar across flow pathways and antecedent conditions.•Dissolved P concentration was ...dependent upon the position of the groundwater table.•Groundwater comprised the largest fraction of total tile discharge during the study.•Water, nutrient, and tracer fluxes revealed new insights into nutrient delivery.
Apportioning sources, assessing flow pathways, and quantifying the interaction between source and transport factors are critical for decreasing nutrient loss from agricultural catchments. In this study, water, nutrient, and tracer (δ18O, electrical conductivity) fluxes were measured over two years from a tile-drained field in Indiana, USA to quantify linkages among water flow pathways, management practices, and nutrient delivery to tile drains. Three-component hydrograph separation showed that tile discharge was, on average, sourced from groundwater (65 ± 31%), shallow soil water (10–20-cm deep; 29 ± 28%), and precipitation (6 ± 8%). Daily nitrate-N (NO3-N) and dissolved reactive phosphorus (DRP) load ranged from 0.0 to 1.8 kg ha−1 and 0–101 g ha−1, respectively, while cumulative loads were 30.7 kg ha−1 and 1,040 g ha−1. Nutrient management practices (fertilizer rate, placement, timing) directly influenced the magnitude of incidental nutrient loss and proportion of load that was derived from a fertilizer source. It was estimated that 52% and 46% of cumulative NO3-N and DRP load, respectively, was incidental loss that occurred within 30 d of fertilizer application. Continuous re-distribution of NO3-N throughout the soil profile following fertilizer application resulted in a broad range of concentration across flow pathways and antecedent conditions. In contrast, dry conditions with tile water sourced from shallow soil water or precipitation resulted in greater, but more variable, DRP concentration compared to wetter conditions when tile water was largely comprised of groundwater. Findings suggest that groundwater table dynamics exerted a strong control over DRP concentration, as similar surface-tile hydrologic connectivity occurred during both dry and wet conditions but produced different water quality outcomes. Groundwater may therefore serve both as a chemical and hydrologic buffer of DRP concentration. Combined measurements of water, nutrient, and tracer fluxes revealed novel insights into processes controlling nutrient delivery to tile drains, with direct applicability for conservation practice implementation and improving process representation in models.
•The far-infrared rotational spectrum of natural water vapor is studied by FTS with a synchrotron radiation source.•454 lines of the 2867 water lines measured in the 50–720 cm-1 region are observed ...for the first time by absorption spectroscopy.•A few position deviations are noted compared to the HITRAN2020 and W2020 line lists.•For H216O, a better agreement is achieved with positions calculated using the effective Bending–Rotation Hamiltonian approach.
The rotational spectrum of water vapor in natural isotopic abundance has been recorded by high resolution (≈ 0.001 cm-1) Fourier transform spectroscopy at the AILES beam line of the SOLEIL synchrotron. The room temperature absorption spectrum has been recorded between 50 and 720 cm-1 using five pressure values up to 7 mbar and an absorption pathlength of 151.75 m. Line parameters were retrieved for the five recorded spectra and then combined in a global list of 2867 water lines with line intensity ranging between a few 10–26 and 10–19 cm/molecule. 454 of the measured lines are newly observed by absorption spectroscopy. The spectral calibration based on a statistical matching with about 700 accurate reference line positions allows for line center determinations with an accuracy of 5 × 10–5 cm-1 for well isolated lines of intermediate intensity.
The large spectral coverage, the achieved position accuracy and sensitivity of the constructed line list make it valuable for validation tests of the current spectroscopic databases. Six water isotopologues (H218O, H216O, H217O, HD18O, HD16O, and HD17O) were found to contribute to the spectrum. The line position comparison to the recent HITRAN2020 spectroscopic database and to the W2020 line lists of H216O, H217O and H218O, Furtenbacher et al. J. Phys. Chem. Ref. Data 49 (2020) 043103; https://doi.org/10.1063/5.0030680 shows an overall very good agreement. Nevertheless, a number of significant deviations are observed. Part of them has an amplitude largely exceeding the W2020 claimed error bars. On the basis of the experimental data at disposal for the main isotopologue (1310 transitions), the best agreement is achieved with the positions calculated using the effective Bending–Rotation Hamiltonian Coudert et al. J Mol Spectrosc 2014;303:36–41. https://doi.org/10.1016/j.jms.2014.07.003.
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Through the modification of mesoporous silica (SBA-15), a hydrophobic microscopic reaction environment was constructed, which was beneficial to improve the catalytic activity of the LPCE reaction. ...The Pt@SBA-15-tetramethyldisilazane catalyst is prepared by the modification of the SBA-15 carrier and the loading of metal Pt, with a water contact angle of 158°. This superhydrophobic structure can enhance the catalytic performance and can prevent the deactivation of the catalyst. By measuring the actual catalytic performance of tritium water under different conditions, we found that it has good catalytic activity, and the catalyst can still maintain a high catalytic activity after 30 days in tritium water environment.
•The superhydrophobic SBA-15 support was synthesized by the modification of silane coupling agent.•Spherical porous self-supporting hydrophobic catalysts were successfully prepared.•The hydrogen-water isotope exchange was used to evaluate the catalytic performance in tritium water.•The high performance and stability of the catalyst show promise in tritium water treatment.
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