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Berlin Brandenburg

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  • Wiley (CrossRef)  (38)
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  • 1
    In: Hydrological Processes, 01 January 2017, Vol.31(1), pp.15-19
    Description: Preferential flow is of high relevance for runoff generation, transport of chemicals and nutrients, and the transit time distribution of water in the soil or watershed. However, preferential flow effects are generally ignored in lumped hydrological models. And even most physically‐based models ignore macropores and preferential flow features at the soil and hillslope scale. Keith Beven was never satisfied with this situation and he tried again and again to convince the scientific community to focus their research on the complex topic of macropore and preferential flow. Although he recognized how difficult it is to correctly include preferential flow in hydrological models, he made substantial progress defining and describing macropore flow and showing its relevance, developing models to simulate preferential flow, and in particular, the interaction between macropores and the soil matrix. In this short commentary, I reflect on these achievements and outline a vision for research in preferential flow experiments and modeling.
    Keywords: Infiltration ; Macropore Flow ; Preferential Flow ; Runoff Generation
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 2
    In: New Phytologist, May 2016, Vol.210(3), pp.839-849
    Description: Plants rely primarily on rainfall infiltrating their root zones – a supply that is inherently variable, and fluctuations are predicted to increase on most of the Earth's surface. Yet, interrelationships between water availability and plant use on short timescales are difficult to quantify and remain poorly understood. To overcome previous methodological limitations, we coupled high‐resolution in situ observations of stable isotopes in soil and transpiration water. We applied the approach along with Bayesian mixing modeling to track the fate of 2H‐labeled rain pulses following drought through soil and plants of deciduous tree ecosystems. We resolve how rainwater infiltrates the root zones in a nonequilibrium process and show that tree species differ in their ability to quickly acquire the newly available source. Sessile oak (Quercus petraea) adjusted root uptake to vertical water availability patterns under drought, but readjustment toward the rewetted topsoil was delayed. By contrast, European beech (Fagus sylvatica) readily utilized water from all soil depths independent of water depletion, enabling faster uptake of rainwater. Our results demonstrate that species‐specific plasticity and responses to water supply fluctuations on short timescales can now be identified and must be considered to predict vegetation functional dynamics and water cycling under current and future climatic conditions. See also the Commentary on this article by
    Keywords: Climate Change ; Deciduous Trees ; Ecohydrology ; Laser Spectroscopy ; Plant–Water Relations ; Root Uptake ; Soil Water ; Stable Isotopes
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 3
    In: Geophysical Research Letters, 16 September 2014, Vol.41(17), pp.6174-6183
    Description: Streamflow drought response depends to a large degree on groundwater recharge. To better predict and preempt streamflow droughts, the relationship between recharge deficit and streamflow response needs to be studied more systematically. We present a combined soil‐vegetation‐atmosphere transfer and conceptual groundwater model experiment that applies a novel set of recharge scenarios preceding drought events in humid‐temperate catchments with different dominant aquifer types. The recharge scenarios are based on the permutation of historical time series and on modified time series matching extreme (50 year) drought events. Karstic and fractured aquifers show short‐term sensitivity to drought with an event‐specific relationship between recharge and streamflow response. Porous and complex aquifers show long‐term sensitivity and a more catchment‐controlled propagation of drought. The sensitivity of drought deficit and recovery time correlates with the water age distribution in baseflow, which is trackable in the groundwater model and a characteristic that should be exploited to improve streamflow drought prediction. Recharge scenarios drive groundwater models to exacerbate streamflow droughtsShort‐ and long‐term sensitivity to drought can be explained by aquifer typesWater age correlates with drought deficit and recovery time
    Keywords: Drought ; Groundwater/Surface Water Interaction ; Modeling ; Water Budgets ; Extreme Events ; Streamflow
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 4
    In: Hydrological Processes, 15 February 2014, Vol.28(4), pp.1916-1930
    Description: Monitoring runoff generation processes in the field is a prerequisite for developing conceptual hydrological models and theories. At the same time, our perception of hydrological processes strongly depends on the spatial and temporal scale of observation. Therefore, the aim of this study is to investigate interactions between runoff generation processes of different spatial scales (plot scale, hillslope scale, and headwater scale). Different runoff generation processes of three hillslopes with similar topography, geology and soil properties, but differences in vegetation cover (grassland, coniferous forest, and mixed forest) within a small v‐shaped headwater were measured: water table dynamics in wells with high spatial and temporal resolution, subsurface flow (SSF) of three 10 m wide trenches at the bottom of the hillslopes subdivided into two trench sections each, overland flow at the plot scale, and catchment runoff. Bachmair . ([Bachmair S, 2012]) found a high spatial variability of water table dynamics at the plot scale. In this study, we investigate the representativity of SSF observations at the plot scale the hillslope scale and vice versa, and the linkage between hillslope dynamics (SSF and overland flow) and streamflow. Distinct differences in total SSF within each 10 m wide trench confirm the high spatial variability of the water table dynamics. The representativity of plot scale observations for hillslope scale SSF strongly depends on whether or not wells capture spatially variable flowpaths. At the grassland hillslope, subsurface flowpaths are not captured by our relatively densely spaced wells (3 m), despite a similar trench flow response to the coniferous forest hillslope. Regarding the linkage between hillslope dynamics and catchment runoff, we found an intermediate to high correlation between streamflow and hillslope hydrological dynamics (trench flow and overland flow), which highlights the importance of hillslope processes in this small watershed. Although the total contribution of SSF to total event catchment runoff is rather small, the contribution during peak flow is moderate to substantial. Additionally, there is process synchronicity between spatially discontiguous measurement points across scales, potentially indicating subsurface flowpath connectivity. Our findings stress the need for (i) a combination of observations at different spatial scales, and (ii) a consideration of the high spatial variability of SSF at the plot and hillslope scale when designing monitoring networks and assessing hydrological connectivity. Copyright © 2013 John Wiley & Sons, Ltd.
    Keywords: Subsurface Flow ; Preferential Flow ; Hillslope Hydrology ; Scale Effects ; Hydrological Connectivity ; Monitoring Networks
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 5
    In: Hydrological Processes, 01 January 2018, Vol.32(1), pp.160-166
    Description: Quantifying the components of rain, snowmelt, and glacier ice melt in river discharge is an important but difficult task in hydrology. Although it forms the basis of many climate impact assessments, many published modelling results do not clearly describe how they derived the discharge components. Consequently, reported components such as absolute amounts or relative percentages of snow and ice melt from different studies are rarely comparable. This commentary revisits the differences in the terminology used, the modelling approaches, and the possible conclusions for effects at different time scales. We argue that for questions related to changes in discharge, not particle tracking, for which methodology is widely available, but instead, an “effect tracking” of the input contributions is important, that is, the representation of the signals of rainfall, snowmelt, and glacier ice melt in the discharge at the catchment outlet. We introduce and briefly describe a method for effect tracking and discuss the differences and advantages compared to other methods. This comparison supports our call to the modelling community for more precise descriptions of how the generated input contributions into a catchment from rainfall, snowmelt, and glacier ice melt are tracked through the catchments' multiple stores to finally compose the presented hydrographs.
    Keywords: Glaciers – Analysis ; Rivers – Analysis ; Hydrology – Analysis;
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 6
    Language: English
    In: Water resources research, 2015, Vol. 51(9), pp. 7777-7784
    Description: We believe that there are too many models in hydrology and we should ask ourselves the question, if we are currently wasting time and effort in developing another model again instead of focusing on the development of a Community Hydrological Model. In other fields, this kind of models has been quite successful, but due to several reasons, no single community model has been developed in the field of hydrology yet. The concept, strength, and weakness of a community model were discussed at the Chapman Conference on Catchment Spatial Behaviour and Complex Organisation held in Luxembourg in September 2014. This discussion as well as our own opinions about the potential of a community models or at least the necessary discussion to establish one are debated in this commentary.
    Keywords: Hydrological Model ; Community Model ; Perceptual Models ; Model Framework ; Natural Sciences ; Earth And Related Environmental Sciences ; Oceanography, Hydrology And Water Resources ; Naturvetenskap ; Geovetenskap Och Miljövetenskap ; Oceanografi, Hydrologi Och Vattenresurser
    ISSN: 0043-1397
    E-ISSN: 19447973
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  • 7
    In: Annals of Neurology, December 2015, Vol.78(6), pp.939-948
    Description: Objective The aim of this work was to localize and quantify alterations of nerve microstructure in diabetic polyneuropathy (DPN) by magnetic resonance (MR) neurography with large anatomical coverage. Methods Patients (N=25) with mild-to-moderate (Neuropathy-Symptom-Score [NSS]/Neuropathy Deficit Score [NDS] 3.8 plus or minus 0.3/2.6 plus or minus 0.5) and patients (n=10) with severe DPN (6.2 plus or minus 0.6/7.4 plus or minus 0.5) were compared to patients (n=15) with diabetes but no DPN and to age-/sex-matched nondiabetic controls (n=25). All subjects underwent MR neurography with large spatial coverage and high resolution from spinal nerve to ankle level: four slabs per leg, each with 35 axial slices (T2- and proton-density-weighted two dimensional turbo-spin-echo sequences; voxel size: 0.40.33.5mm super(3)) and a three-dimensional T2-weighted sequence to cover spinal nerves and plexus. Nerve segmentation was performed on a total of 280 slices per subject. Nerve lesion voxels were determined independently from operator input by statistical classification against the nondiabetic cohort. At the site with highest lesion-voxel burden, signal quantification was performed by calculating nerve proton spin density and T2 relaxation time. Results Total burden of nerve lesion voxels was significantly increased in DPN (p=0.003) with strong spatial predominance at thigh level, where average lesion voxel load was significantly higher in severe (57 plus or minus 18.4; p=0.0022) and in mild-to-moderate DPN (35 plus or minus 4.0; p〈0.001) than in controls (18 plus or minus 3.6). Signal quantification at the site of predominant lesion burden (thigh) revealed a significant increase of nerve proton spin density in severe (360 plus or minus 22.9; p=0.043) and in mild-to-moderate DPN (365 plus or minus 15.2; p=0.001) versus controls (288 plus or minus 13.4), but not of T2 relaxation time (p=0.49). Nerve proton spin density predicted severity of DPN with an odds ratio of 2.9 (95% confidence interval: 2.4-3.5; p〈0.001) per 100 proton spins. Interpretation In DPN, the predominant site of microstructural nerve alteration is at the thigh level with a strong proximal-to-distal gradient. Nerve proton spin density at the thigh level is a novel quantitative imaging biomarker of early DPN and increases with neuropathy severity. Ann Neurol 2015; 78:939-948
    Keywords: Statistics ; Protons ; Image Processing ; Biomarkers ; Diabetes Mellitus ; Leg ; Spinal Nerves ; Classification ; Segmentation ; Ankle ; N.M.R. ; Brain Slice Preparation ; Polyneuropathy ; Neuropathy ; Neurology & Neuropathology;
    ISSN: 0364-5134
    E-ISSN: 1531-8249
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  • 8
    In: Wiley Interdisciplinary Reviews: Water, November 2017, Vol.4(6), pp.n/a-n/a
    Description: We review the state‐of‐the‐art of cross‐disciplinary knowledge on phosphorus (P) cycling in temperate forest ecosystems, focused at studies from hydrology, biology, biogeochemistry, soil‐, and geosciences. Changes in soil P stocks during long‐term ecosystem development are addressed briefly; the general ranges of specific P pools and P fluxes within the ecosystem and the presumed underlying processes are covered more in depth. Wherever possible, we differentiate between coniferous and deciduous forests. As the most important P pools, mineral soil, forest floor, vegetation, and microbial biomass are described in terms of pool size, molecular composition, and turnover. Litterfall, soil water seepage, atmospheric deposition, and biotic uptake as the most studied P fluxes in the forest ecosystem are discussed in detail, spotlighting biogeochemical processes relevant for mobilization and retention of P in the rooting zone. Through a meta‐analysis of available literature, we build a dataset that allows the quantification of major P‐cycle components in temperate forests in terms of range and distribution, highlighting similarities and differences between coniferous and deciduous forests. The two forest types are notably distinct in their distribution of P within compartments of the plant biomass and forest floor. The possibility to construct closed local P balances is often hindered by missing information on fluxes of dissolved and particulate P across the ecosystem boundary, be it in the atmosphere, soil, or on the surface. These fluxes are irregular in space and time and feature large overall mass fluxes but comparatively small P fluxes, making the latter one difficult to quantify. 2017, 4:e1243. doi: 10.1002/wat2.1243 This article is categorized under: A schematic respresentation of the Phosphorus cycle in temperate forests. Pools and fluxes are scaled to their average size. See the full paper for more detailed information and data sources.
    Keywords: Phosphorus Cycle ; Phosphorus ; Phosphorus Cycle ; Compartments ; Phosphorus ; Uptake ; Biogeochemistry ; Biomass ; Plant Biomass ; Environmental Changes ; Soil Water ; Pools ; Soil Water ; Distribution ; Composition ; Forests ; Phosphorus Cycle ; Biogeochemistry ; Biogeochemistry ; Biomass ; Biology ; Phosphorus ; Forests ; Microorganisms ; Ecosystems ; Moisture Content ; Forest Floor ; Forest Ecosystems ; Forests ; Stocks ; Hydrology ; Forests ; Rooting ; Pools ; Seepage ; Components ; Hydrology ; Deciduous Forests ; Forest Floor ; Fluxes ; Atmospheric Pollutant Deposition ; Soils ; Hydrology ; Seepage ; Biomass ; Hydrology ; Forest Biomass;
    ISSN: 2049-1948
    E-ISSN: 2049-1948
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  • 9
    In: Journal of Neurochemistry, October 2014, Vol.131(2), pp.251-264
    Description: Human glioblastomas may be hierarchically organized. Within this hierarchy, glioblastoma‐initiating cells have been proposed to be more resistant to radiochemotherapy and responsible for recurrence. Here, established stem cell markers and stem cell attributed characteristics such as self‐renewal capacity and tumorigenicity have been profiled in primary glioblastoma cultures to predict radiosensitivity. Furthermore, the sensitivity to radiotherapy of different subpopulations within a single primary glioblastoma culture was analyzed by a flow cytometric approach using Nestin, SRY (sex‐determining region Y)‐box 2 (SOX2) and glial fibrillary acidic protein. The protein expression of Nestin and SOX2 as well as the mRNA levels of Musashi1, L1 cell adhesion molecule, CD133, Nestin, and pleiomorphic adenoma gene‐like 2 inversely correlated with radioresistance in regard to the clonogenic potential. Only CD44 protein expression correlated positively with radioresistance. In terms of proliferation, Nestin protein expression and Musashi1, pleiomorphic adenoma gene‐like 2, and CD133 mRNA levels are inversely correlated with radioresistance. Higher expression of stem cell markers does not correlate with resistance to radiochemotherapy in the cancer genome atlas glioblastoma collective. SOX2 expressing subpopulations exist within single primary glioblastoma cultures. These subpopulations predominantly form the proliferative pool of the primary cultures and are sensitive to irradiation. Thus, profiling of established stem cell markers revealed a surprising result. Except CD44, the tested stem cell markers showed an inverse correlation between expression and radioresistance. Markers used to define glioma‐initiating cells (GIC) are generally not defining a more resistant, but rather a more sensitive group of glioma cells. An exemption is CD44 expression. Also proliferation of the GIC culture itself was not systematically associated with radiosensitivity or – resistance, but a SOX‐2 positive, proliferative subgroup within a GIC culture is showing the highest radiosensitivity. Markers used to define glioma‐initiating cells (GIC) are generally not defining a more resistant, but rather a more sensitive group of glioma cells. An exemption is CD44 expression. Also proliferation of the GIC culture itself was not systematically associated with radiosensitivity or – resistance, but a SOX‐2 positive, proliferative subgroup within a GIC culture is showing the highest radiosensitivity.
    Keywords: Cd133 ; Glioma‐Initiating Cells ; Profiling ; Radiotherapy Sensitivity ; Sox2 ; Stem Cell Markers
    ISSN: 0022-3042
    E-ISSN: 1471-4159
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  • 10
    In: Ecohydrology, November 2012, Vol.5(6), pp.721-732
    Description: Changes of the land surface affect the water balance components over seasonal, annual and decadal time scales. This study explored the role of vegetation cover transitions on evapotranspiration in forested watersheds of the North American West. We applied empirical time‐recovery functions describing the impact of forest removal and subsequent regrowth on actual evapotranspiration () or runoff. A generalized function () was adapted to the North American West and tested using three different datasets of observed or estimated in forest chronosequences: from flux towers equipped with eddy covariance sensors, estimated from the water balance in experimental paired watersheds and in a set of gauged watersheds with considerable forest cover history dating back to the 18th century. from the first two datasets showed a behaviour similar to the K‐curve, although the timing and the magnitude differed substantially. To reconstruct long‐term changes in for the gauged watersheds, we applied a transfer function approach linking the K‐curve and the reconstructed forest cover history at the watershed scale. In several watersheds, correlation coefficients between the reconstructed changes and the annual water balances suggest that changes in time were driven by the land cover transitions. In watersheds with low correlations, disturbance activities peaked before the 20th century, and the effects of vegetation have phased out in the period of streamflow observations. The findings of this paper suggest that trends in the observed water balance in forested watersheds can be associated to land cover disturbances well before the start of hydro‐climatic observations. Copyright © 2011 John Wiley & Sons, Ltd.
    Keywords: Forest Disturbance ; Recovery ; Evapotranspiration ; Stand Age ; North American West ; Water Balance ; Forest Cover History ; Eddy Covariance Fluxes
    ISSN: 1936-0584
    E-ISSN: 1936-0592
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