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Berlin Brandenburg

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  • 1
    Article
    Article
    Language: English
    In: Science (New York, N.Y.), 06 January 2017, Vol.355(6320), pp.102
    Description: “So you want to be a writer?” one of my professors asked me when he learned I was interested in a career as an academic scientist—a pointed warning that a life of science is also a life of writing. But even knowing this in advance, I found that writing was a challenge as I made my way down the
    Keywords: Sciences (General) ; Biology;
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 2
    Article
    Article
    Language: English
    In: Science (New York, N.Y.), 15 September 2017, Vol.357(6356), pp.1202
    Description: After I started out in a university faculty position nearly 30 years ago, the early years were rough. Not because of problems, exactly, but because of opportunities—too many of them. I did not know how much was enough, so I just did more and more. As a result, I lived a life distracted, both at
    Keywords: Sciences (General) ; Biology;
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 3
    In: Nature, 2017, Vol.547(7664), p.483
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 4
    In: Nature, 2015, Vol.525(7567), p.91
    Description: Current land surface models assume that groundwater, streamflow and plant transpiration are all sourced and mediated by the same well mixed water reservoir--the soil. However, recent work in Oregon (1) and Mexico (2) has shown evidence of ecohydrological separation, whereby different subsurface compartmentalized pools of water supply either plant transpiration fluxes or the combined fluxes of groundwater and streamflow. These findings have not yet been widely tested. Here we use hydrogen and oxygen isotopic data ([sup.2]H ([delta][sup.2]H) and [sup.18]O/[sup.16]O ([delta][sup.18]O)) from 47 globally distributed sites to show that ecohydrological separation is widespread across different biomes. Precipitation, stream water and groundwater from each site plot approximately along the [delta][sup.2]H/[delta][sup.18]O slope of local precipitation inputs. But soil and plant xylem waters extracted from the 47 sites all plot below the local stream water and groundwater on the meteoric water line, suggesting that plants use soil water that does not itself contribute to groundwater recharge or streamflow. Our results further show that, at 80% of the sites, the precipitation that supplies groundwater recharge and streamflow is different from the water that supplies parts of soil water recharge and plant transpiration. The ubiquity of subsurface water compartmentalization found here, and the segregation of storm types relative to hydrological and ecological fluxes, may be used to improve numerical simulations of runoff generation, stream water transit time and evaporation-transpiration partitioning. Future land surface model parameterizations should be closely examined for how vegetation, groundwater recharge and streamflow are assumed to be coupled.
    Keywords: Transpiration – Natural History ; Groundwater – Natural History ; Streamflow – Natural History;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 5
    Language: English
    In: Ecological Modelling, 24 February 2015, Vol.298, pp.64-74
    Description: Runoff generation at the hillslope scale is an important component of the hydrological cycle. Recent work has shown that a common hillslope runoff response mechanism is driven by connectivity of saturated patches in the subsurface (via filling and spilling) to a threshold initiation of lateral flow at the hillslope base. Here, we show that directed percolation theory is able to represent this key runoff process including the details of dynamical flowpath development and filling and spilling processes at the soil-bedrock interface. We then use the directed percolation model to investigate how changes in slope angle, soil depth, and subsurface microtopography influence stormflow response. We map the evolving subsurface flow network under different hillslope classes and compare them to the natural system response. Our results suggest that the natural system sheds water more efficiently than randomly generated systems providing some insights into key hydrogeomorphic controls on water shedding in the environment.
    Keywords: Hillslope Hydrology ; Soil ; Runoff Model ; Connectivity ; Directed Percolation ; Environmental Sciences ; Ecology
    ISSN: 0304-3800
    E-ISSN: 1872-7026
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  • 6
    Language: English
    In: Ecological Modelling, Feb 24, Vol.298, p.64(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ecolmodel.2014.06.024 Byline: Daryl Janzen, Jeffrey J. McDonnell Abstract: * We use directed percolation theory to model hillslope hydrological response. * We examine flow path dynamics of fill, spill, connectivity and associated threshold. * We explore various factors that affect the pattern and timing of hillslope runoff. * Soil and topographic heterogeneities control complex non-linear response. * Evidence that hydrogeomorphic processes conspire to optimise hillslope drainage. Author Affiliation: (a) Global Institute for Water Security, University of Saskatchewan, Saskatoon, Canada (b) School of Geosciences, University of Aberdeen, Aberdeen, Scotland, UK (c) Dept. of Forest Engineering, Resources and Management, Oregon State University, Corvallis, OR, USA
    Keywords: Runoff ; Geomorphology ; Flow (Dynamics)
    ISSN: 0304-3800
    Source: Cengage Learning, Inc.
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  • 7
    Language: English
    In: Journal of Hydrology, 2010, Vol.393(1), pp.77-93
    Description: Hillslope hydrological response to precipitation is extremely complex and poorly modeled. One possible approach for reducing the complexity of hillslope response and its mathematical parameterization is to look for macroscale hydrological behavior. Hillslope threshold response to storm precipitation is one such macroscale behavior observed at field sites across the globe. Nevertheless, the relative controls on the precipitation–discharge threshold poorly known. This paper presents a combined model development, calibration and testing experiment study to investigate the primary controls on the observed precipitation–discharge threshold relationship. We focus on the dominant hydrological processes revealed in part one of this two-part paper and with our new numerical model, replicate the threshold response seen in the discharge record and other hydrometric and tracer data available at the site. We then present a series of virtual experiments designed to probe the controls on the threshold response. We show that the threshold behavior is due to a combination of environmental (storm spacing and potential evapotranspiration) and geologic (bedrock permeability and bedrock topography) factors. The predicted precipitation–discharge threshold subsumes the complexity of plot-scale soil water response. We then demonstrate its use for prediction of whole-catchment storm discharge at other first order catchments at Maimai and the HJ Andrews Experimental Forest in Oregon.
    Keywords: Preferential Flow ; Hillslope Hydrology ; Numeric Models ; Model Calibration ; Virtual Experiments ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 8
    Language: English
    In: Science of the Total Environment, 01 October 2017, Vol.595, pp.486-493
    Description: Using stable isotope data from soil and vegetation xylem samples across a range of landscape positions, this study provides preliminary insights into spatial patterns and temporal dynamics of soil-plant water interactions in a humid, low-energy northern environment. Our analysis showed that evaporative fractionation affected the isotopic signatures in soil water at shallow depths but was less marked than previously observed in other environments. By comparing the temporal dynamics of stable isotopes in soil water mainly held at suctions around and below field capacity, we found that these waters are not clearly separated. The study inferred that vegetation water sources at all sites were relatively constant, and most likely to be in the upper profile close to the soil/atmosphere interface. The data analyses also suggested that both vegetation type and landscape position, including soil type, may have a strong influence on local water uptake patterns, although more work is needed to explicitly identify water sources and understand the effect of plant physiological processes on xylem isotopic water signatures.
    Keywords: Vegetation Water Use ; Soil Water Storage ; Isotopes ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 9
    Language: English
    In: Journal of Hydrology, 2015, Vol.522, p.58(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2014.12.029 Byline: Scott T. Allen, Richard F. Keim, Jeffrey J. McDonnell Abstract: * The mean event range of spatial variation for throughfall [delta].sup.18O was 1.4a[degrees]. * Unstable spatial patterns of [delta].sup.18O among events smoothed variation in seasonal [delta].sup.18O. * A Monte-Carlo analysis quantified sampling error for multiple sampling schemes. * Roving collectors do not reduce error in estimating cumulative isotopic composition. Article History: Received 22 May 2014; Revised 20 October 2014; Accepted 13 December 2014 Article Note: (miscellaneous) This manuscript was handled by Laurent Charlet, Editor-in-Chief, with the assistance of Fereidoun Rezanezhad, Associate Editor
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 10
    Language: English
    In: Journal of Hydrology, March 2015, Vol.522, pp.58-66
    Description: Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.
    Keywords: Stable Isotopes ; Spatiotemporal Variability ; Sampling Error ; Net Precipitation ; Canopy Interception ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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