@article{ZimmermannZimmermannScheckenbachetal.2013, author = {Zimmermann, B. and Zimmermann, Alexander and Scheckenbach, H. L. and Schmid, T. and Hall, Jefferson. S. and van Breugel, Michiel}, title = {Changes in rainfall interception along a secondary forest succession gradient in lowland Panama}, series = {Hydrology and earth system sciences : HESS}, volume = {17}, journal = {Hydrology and earth system sciences : HESS}, number = {11}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-17-4659-2013}, pages = {4659 -- 4670}, year = {2013}, abstract = {Secondary forests are rapidly expanding in tropical regions. Yet, despite the importance of understanding the hydrological consequences of land-cover dynamics, the relationship between forest succession and canopy interception is poorly understood. This lack of knowledge is unfortunate because rainfall interception plays an important role in regional water cycles and needs to be quantified for many modeling purposes. To help close this knowledge gap, we designed a throughfall monitoring study along a secondary succession gradient in a tropical forest region of Panama. The investigated gradient comprised 20 forest patches 3 to 130 yr old. We sampled each patch with a minimum of 20 funnel-type throughfall collectors over a continuous 2month period that had nearly 900 mm of rain. During the same period, we acquired forest inventory data and derived several forest structural attributes. We then applied simple and multiple regression models (Bayesian model averaging, BMA) and identified those vegetation parameters that had the strongest influence on the variation of canopy interception. Our analyses yielded three main findings. First, canopy interception changed rapidly during forest succession. After only a decade, throughfall volumes approached levels that are typical for mature forests. Second, a parsimonious (simple linear regression) model based on the ratio of the basal area of small stems to the total basal area outperformed more complex multivariate models (BMA approach). Third, based on complementary forest inventory data, we show that the influence of young secondary forests on interception in realworld fragmented landscapes might be detectable only in regions with a substantial fraction of young forests. Our re-sults suggest that where entire catchments undergo forest regrowth, initial stages of succession may be associated with a substantial decrease of streamflow generation. Our results further highlight the need to study hydrological processes in all forest succession stages, including early ones.}, language = {en} } @article{ZimmermannZimmermannTurneretal.2014, author = {Zimmermann, Beate and Zimmermann, Alexander and Turner, Benjamin L. and Francke, Till and Elsenbeer, Helmut}, title = {Connectivity of overland flow by drainage network expansion in a rain forest catchment}, series = {Water resources research}, volume = {50}, journal = {Water resources research}, number = {2}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0043-1397}, doi = {10.1002/2012WR012660}, pages = {1457 -- 1473}, year = {2014}, abstract = {Soils in various places of the Panama Canal Watershed feature a low saturated hydraulic conductivity (K-s) at shallow depth, which promotes overland-flow generation and associated flashy catchment responses. In undisturbed forests of these areas, overland flow is concentrated in flow lines that extend the channel network and provide hydrological connectivity between hillslopes and streams. To understand the dynamics of overland-flow connectivity, as well as the impact of connectivity on catchment response, we studied an undisturbed headwater catchment by monitoring overland-flow occurrence in all flow lines and discharge, suspended sediment, and total phosphorus at the catchment outlet. We find that connectivity is strongly influenced by seasonal variation in antecedent wetness and can develop even under light rainfall conditions. Connectivity increased rapidly as rainfall frequency increased, eventually leading to full connectivity and surficial drainage of entire hillslopes. Connectivity was nonlinearly related to catchment response. However, additional information on factors such as overland-flow volume would be required to constrain relationships between connectivity, stormflow, and the export of suspended sediment and phosphorus. The effort to monitor those factors would be substantial, so we advocate applying the established links between rain event characteristics, drainage network expansion by flow lines, and catchment response for predictive modeling and catchment classification in forests of the Panama Canal Watershed and in similar regions elsewhere.}, language = {en} } @article{BoggioBodenmuellerFrembergetal.2014, author = {Boggio, Jose M. Chavez and Bodenmueller, D. and Fremberg, T. and Haynes, R. and Roth, Martin M. and Eisermann, R. and Lisker, M. and Zimmermann, L. and Boehm, Michael}, title = {Dispersion engineered silicon nitride waveguides by geometrical and refractive-index optimization}, series = {Journal of the Optical Society of America : B, Optical physics}, volume = {31}, journal = {Journal of the Optical Society of America : B, Optical physics}, number = {11}, publisher = {Optical Society of America}, address = {Washington}, issn = {0740-3224}, doi = {10.1364/JOSAB.31.002846}, pages = {2846 -- 2857}, year = {2014}, abstract = {Dispersion engineering in silicon nitride (SiXNY) waveguides is investigated through the optimization of the waveguide transversal dimensions and refractive indices in a multicladding arrangement. Ultraflat dispersion of -84.0 +/- 0.5 ps/nm/km between 1700 and 2440 nm and 1.5 +/- 3 ps/nm/km between 1670 and 2500 nm is numerically demonstrated. It is shown that typical refractive index fluctuations as well as dimension fluctuations during fabrication of the SiXNY waveguides are a limitation for obtaining ultraflat dispersion profiles. Single- and multicladding waveguides are fabricated and their dispersion profiles measured (over nearly 1000 nm) using a low-coherence frequency domain interferometric technique. By appropriate thickness optimization, the zero-dispersion wavelength is tuned over a large spectral range in single-and multicladding waveguides with small refractive index contrast (3\%). A flat dispersion profile with +/- 3.2 ps/nm/km variation over 500 nm is obtained in a multicladding waveguide fabricated with a refractive index contrast of 37\%. Finally, we generate a nearly three-octave supercontinuum in this dispersion flattened multicladding SiXNY waveguide. (C) 2014 Optical Society of America}, language = {en} } @article{BartholdTurnerElsenbeeretal.2017, author = {Barthold, Frauke Katrin and Turner, Benjamin L. and Elsenbeer, Helmut and Zimmermann, Alexander}, title = {A hydrochemical approach to quantify the role of return flow in a surface flow-dominated catchment}, series = {Hydrological processes}, volume = {31}, journal = {Hydrological processes}, number = {5}, publisher = {Wiley}, address = {Hoboken}, issn = {0885-6087}, doi = {10.1002/hyp.11083}, pages = {1018 -- 1033}, year = {2017}, abstract = {Stormflow generation in headwater catchments dominated by subsurface flow has been studied extensively, yet catchments dominated by surface flow have received less attention. We addressed this by testing whether stormflow chemistry is controlled by either (a) the event-water signature of overland flow, or (b) the pre-event water signature of return flow. We used a high-resolution hydrochemical data set of stormflow and end-members of multiple storms in an end-member mixing analysis to determine the number of end-members needed to explain stormflow, characterize and identify potential end-members, calculate their contributions to stormflow, and develop a conceptual model of stormflow. The arrangement and relative positioning of end-members in stormflow mixing space suggest that saturation excess overland flow (26-48\%) and return flow from two different subsurface storage pools (17-53\%) are both similarly important for stormflow. These results suggest that pipes and fractures are important flow paths to rapidly release stored water and highlight the value of within-event resolution hydrochemical data to assess the full range and dynamics of flow paths.}, language = {en} } @article{PlenerZohselHohmetal.2017, author = {Plener, Paul L. and Zohsel, Katrin and Hohm, Erika and Buchmann, Arlette F. and Banaschewski, T. and Zimmermann, Ulrich S. and Laucht, Manfred}, title = {Lower cortisol level in response to a psychosocial stressor in young females with self-harm}, series = {Psychoneuroendocrinology}, volume = {76}, journal = {Psychoneuroendocrinology}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4530}, doi = {10.1016/j.psyneuen.2016.11.009}, pages = {84 -- 87}, year = {2017}, abstract = {Background: Self-harm is highly prevalent in adolescence, often serving an emotion regulation function. Social stressors such as bullying are associated with self-harm. The neurobiological background of the relationship between social stressors and self-harm needs to be further understood to inform prevention and therapy. Methods: Participants were members of an epidemiological cohort study. 130 female participants underwent the Trier Social Stress Test (TSST) at age 19. Of them, 21 reported a history of self-harm as assessed by the Youth Self Report. Psychiatric diagnoses were recorded. Results: Participants with a history of self-harm showed significantly lower blood cortisol levels throughout the TSST. Early psychosocial adversity did not significantly differ between groups with and without self-harm, with self-harming participants reporting more childhood adversities. Conclusion: These results add to the limited field of studies showing an altered HPA axis activity in females with self-harm. Future studies need to address the causal mechanisms behind this association.}, language = {en} } @misc{SeboldGarbusowNebeetal.2018, author = {Sebold, Miriam and Garbusow, Maria and Nebe, S. and Sundmacher, L. and Kuitunen-Paul, S{\"o}ren and Wittchen, H. U. and Smolka, M. and Zimmermann, U. and Rapp, Michael A. and Huys, Q. and Schlagenhauf, Florian and Heinz, A.}, title = {From goals to habits in alcohol dependence}, series = {European psychiatry : the journal of the Association of European Psychiatrists}, volume = {48}, journal = {European psychiatry : the journal of the Association of European Psychiatrists}, publisher = {Elsevier}, address = {Paris}, issn = {0924-9338}, pages = {S274 -- S274}, year = {2018}, language = {en} }