@article{LozanoParravanSchaikSchnabeletal.2016,
  author    = {Lozano-Parra, Javier and van Schaik, N. Loes M. B. and Schnabel, Susanne and Gomez-Gutierrez, Alvaro},
  title     = {Soil moisture dynamics at high temporal resolution in a semiarid Mediterranean watershed with scattered tree cover},
  series = {Hydrological processes},
  volume    = {30},
  journal   = {Hydrological processes},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0885-6087},
  doi       = {10.1002/hyp.10694},
  pages     = {1155 -- 1170},
  year      = {2016},
  abstract  = {Subsurface water flows play a key role in the distribution of water and solutes and thereby in the water availability for plants. However, the characterization of different flow processes (i.e.matrix and preferential flow), the frequency and factors that cause them, is relatively rare. This characterization enables a better understanding of spatio-temporal variability of water resources and allows for the design of models to be improved. Using a method based on the time derivative of soil moisture variation known as maximum wetting slope, types of soil wetting processes were classified and quantified. For this, capacitance sensors, which registered the volumetric water content at high temporal resolution (30min) for more than two hydrological years, were installed at different depths and placed in soil moisture stations with different vegetation covers, lithology and topographic position. Results indicated that there is a general behaviour or pattern of soil moisture dynamics in the catchment with a dominant occurrence of slower soil wetting processes (>50\%), caused by matrix flows, and a low occurrence of those faster processes (<30\%), originated by preferential flows. Nevertheless, when the total volume of water is considered, preferential flow becomes the dominant process, so that the ecological role of both flow types becomes prominent in water-limited environments. Statistical multivariate analyses based on data-mining techniques proved that although both flow types depend on variables associated with precipitation and antecedent soil moisture conditions, faster soil wetting processes are mainly related to variables such as rainfall intensity and topography, while slower soil wetting processes are related to flow velocity, soils or vegetation. Copyright (c) 2015 John Wiley \& Sons, Ltd.},
  language  = {en}
}
@article{AllroggenvanSchaikTronicke2015,
  author    = {Allroggen, Niklas and van Schaik, N. Loes M. B. and Tronicke, Jens},
  title     = {4D ground-penetrating radar during a plot scale dye tracer experiment},
  series = {Journal of applied geophysics},
  volume    = {118},
  journal   = {Journal of applied geophysics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0926-9851},
  doi       = {10.1016/j.jappgeo.2015.04.016},
  pages     = {139 -- 144},
  year      = {2015},
  abstract  = {Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{vanSchaikBronstertdeJongetal.2014,
  author    = {van Schaik, N. Loes M. B. and Bronstert, Axel and de Jong, S. M. and Jetten, V. G. and van Dam, J. C. and Ritsema, C. J. and Schnabel, Susanne},
  title     = {Process-based modelling of a headwater catchment in a semi-arid area: the influence of macropore flow},
  series = {Hydrological processes},
  volume    = {28},
  journal   = {Hydrological processes},
  number    = {24},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0885-6087},
  doi       = {10.1002/hyp.10086},
  pages     = {5805 -- 5816},
  year      = {2014},
  abstract  = {Subsurface stormflow is thought to occur mainly in humid environments with steep terrains. However, in semi-arid areas, preferential flow through macropores can also result in a significant contribution of subsurface stormflow to catchment runoff for varying catchment conditions. Most hydrological models neglect this important subsurface preferential flow. Here, we use the process-oriented hydrological model Hillflow-3D, which includes a macropore flow approach, to simulate rainfall-runoff in the semi-arid Parapunos catchment in Spain, where macropore flow was observed in previous research. The model was extended for this study to account for sorptivity under very dry soil conditions. The results of the model simulations with and without macropore flow are compared. Both model versions give reasonable results for average rainfall situations, although the approach with the macropore concept provides slightly better results. The model results for scenarios of extreme rainfall events (>13.3mm30min(-1)) however show large differences between the versions with and without macropores. These model results compared with measured rainfall-runoff data show that the model with the macropore concept is better. Our conclusion is that preferential flow is important in controlling surface runoff in case of specific, high intensity rainfall events. Therefore, preferential flow processes must be included in hydrological models where we know that preferential flow occurs. Hydrological process models with a less detailed process description may fit observed average events reasonably well but can result in erroneous predictions for more extreme events. Copyright (c) 2013 John Wiley \& Sons, Ltd.},
  language  = {en}
}
@article{PalmvanSchaikSchroederEsselbach2013,
  author    = {Palm, Juliane and van Schaik, N. Loes M. B. and Schr{\"o}der-Esselbach, Boris},
  title     = {Modelling distribution patterns of anecic, epigeic and endogeic earthworms at catchment-scale in agro-ecosystems},
  series = {Pedobiologia : international journal of soil biology},
  volume    = {56},
  journal   = {Pedobiologia : international journal of soil biology},
  number    = {1},
  publisher = {Elsevier},
  address   = {Jena},
  issn      = {0031-4056},
  doi       = {10.1016/j.pedobi.2012.08.007},
  pages     = {23 -- 31},
  year      = {2013},
  abstract  = {Species distribution models are useful for identifying driving environmental factors that determine earthworm distributions as well as for predicting earthworm distribution patterns and abundances at different scales. However, due to large efforts in data acquisition, studies on larger scales are rare and often focus on single species or earthworms in general. In this study, we use boosted regression tree models (BRTs) for predicting the distribution of the three functional earthworm types, i.e. anecics, endogeics and epigeics, in an agricultural area in Baden-Wurttemberg (Southwest Germany). First, we predicted presence and absence and later earthworm abundances, considering predictors depicting land management, topography, and soil conditions as well as biotic interaction by using the abundance of the other functional earthworm types. The final presence-absence models performed reasonably well, with explained deviances between 24 and 51\% after crossvalidation. Models for abundances of anecics and endogeics were less successful, since the high small-scale variability and patchiness in earthworm abundance influenced the representativeness of the field measurements. This resulted in a significant model uncertainty, which is practically very difficult to overcome with earthworm sampling campaigns at the catchment scale. Results showed that management practices (i.e. disturbances), topography, soil conditions, and biotic interactions with other earthworm groups are the most relevant predictors for spatial distribution (incidence) patterns of all three functional groups. The response curves and contributions of predictors differ for the three functional earthworm types. Epigeics are also controlled by topographic features, endogeics by soil parameters.},
  language  = {en}
}