TY - GEN A1 - Rolinski, Susanne A1 - Rammig, Anja A1 - Walz, Ariane A1 - von Bloh, Werner A1 - van Oijen, M. A1 - Thonicke, Kirsten T1 - A probabilistic risk assessment for the vulnerability of the European carbon cycle to weather extremes BT - The ecosystem perspective T2 - Postprints der Universität Potsdam : Mathematisch naturwissenschaftliche Reihe (487) N2 - Extreme weather events are likely to occur more often under climate change and the resulting effects on ecosystems could lead to a further acceleration of climate change. But not all extreme weather events lead to extreme ecosystem response. Here, we focus on hazardous ecosystem behaviour and identify coinciding weather conditions. We use a simple probabilistic risk assessment based on time series of ecosystem behaviour and climate conditions. Given the risk assessment terminology, vulnerability and risk for the previously defined hazard are estimated on the basis of observed hazardous ecosystem behaviour. We apply this approach to extreme responses of terrestrial ecosystems to drought, defining the hazard as a negative net biome productivity over a 12-month period. We show an application for two selected sites using data for 1981-2010 and then apply the method to the pan-European scale for the same period, based on numerical modelling results (LPJmL for ecosystem behaviour; ERA-Interim data for climate). Our site-specific results demonstrate the applicability of the proposed method, using the SPEI to describe the climate condition. The site in Spain provides an example of vulnerability to drought because the expected value of the SPEI is 0.4 lower for hazardous than for non-hazardous ecosystem behaviour. In northern Germany, on the contrary, the site is not vulnerable to drought because the SPEI expectation values imply wetter conditions in the hazard case than in the non-hazard case. At the pan-European scale, ecosystem vulnerability to drought is calculated in the Mediterranean and temperate region, whereas Scandinavian ecosystems are vulnerable under conditions without water shortages. These first model- based applications indicate the conceptual advantages of the proposed method by focusing on the identification of critical weather conditions for which we observe hazardous ecosystem behaviour in the analysed data set. Application of the method to empirical time series and to future climate would be important next steps to test the approach. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 487 KW - global vegetation model KW - climate extremes KW - fire emissions KW - drought KW - forest KW - productivity KW - reduction KW - events KW - assimilation KW - uncertainty Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407999 SN - 1866-8372 IS - 487 SP - 1813 EP - 1831 ER - TY - JOUR A1 - Tu, Rui A1 - Ge, Maorong A1 - Wang, Rongjiang A1 - Walter, Thomas R. T1 - A new algorithm for tight integration of real-time GPS and strong-motion records, demonstrated on simulated, experimental, and real seismic data JF - Journal of seismology N2 - The complementary advantages of GPS and seismic measurements are well recognized in seismotectonic monitoring studies. Therefore, integrated processing of the two data streams has been proposed recently in an attempt to obtain accurate and reliable information of surface displacements associated with earthquakes. A hitherto still critical issue in the integrated processing is real-time detection and precise estimation of the transient baseline error in the seismic records. Here, we report on a new approach by introducing the seismic acceleration corrected by baseline errors into the state equation system. The correction is performed and regularly updated in short epochs (with increments which may be as short as seconds), so that station position, velocity, and acceleration can be constrained very tightly and baseline error can be estimated as a random-walk process. With the adapted state equation system, our study highlights the use of a new approach developed for integrated processing of GPS and seismic data by means of sequential least-squares adjustment. The efficiency of our approach is demonstrated and validated using simulated, experimental, and real datasets. The latter were collected at collocated GPS and seismic stations around the 4 April 2010, E1 Mayor-Cucapah earthquake (Mw, 7.2). The results have shown that baseline errors of the strong-motion sensors are corrected precisely and high-precision seismic displacements are real-timely obtained by the new approach. KW - High-rateGPS KW - Strong-motion records KW - Baseline error KW - Tight integration KW - Precise point positioning Y1 - 2014 U6 - https://doi.org/10.1007/s10950-013-9408-x SN - 1383-4649 SN - 1573-157X VL - 18 IS - 1 SP - 151 EP - 161 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Lohmann, Dirk A1 - Falk, Thomas A1 - Geissler, Katja A1 - Blaum, Niels A1 - Jeltsch, Florian T1 - Determinants of semi-arid rangeland management in a land reform setting in Namibia JF - Journal of arid environments N2 - To assess the ecological and economic implications of the redistributive land reform in semi-arid Namibia, we investigated to what extent land reform beneficiaries adjust herd size and herd composition according to environmental (rainfall, vegetation) and economic variables (herd size, financial assets, running costs). We performed model-based role-plays with Namibian land reform beneficiaries, simulating 10 years of rangeland management. Our study revealed that the farmers surveyed mainly manage their herds according to their economic situation (herd size and account balance) but do not take environmental variability (rainfall and vegetation) into account. Further, our results indicate that, due to financial pressure, farmers are not able to apply their desired management strategies, and that owners of small farms face a higher risk of economic failure. However, farmers apply rather conservative and constant stocking rates and will thus, given the current economic limitations, likely not contribute to semi-arid savanna degradation. We conclude that land reform beneficiaries need support to be able to apply straightforward and efficient management strategies. This could be achieved by facilitating cooperation between small farming businesses and by supporting initial investment in productive cattle herds at the time of redistribution of the land. KW - Dry land degradation KW - Semi-arid savanna KW - Land reform KW - Rangeland management KW - Simulation model KW - Role-play Y1 - 2014 U6 - https://doi.org/10.1016/j.jaridenv.2013.10.005 SN - 0140-1963 SN - 1095-922X VL - 100 SP - 23 EP - 30 PB - Elsevier CY - London ER - TY - JOUR A1 - Sarkar, Saswati A1 - Wilkes, Heinz A1 - Prasad, Sushma A1 - Brauer, Achim A1 - Riedel, Nils A1 - Stebich, Martina A1 - Basavaiah, Nathani A1 - Sachse, Dirk T1 - Spatial heterogeneity in lipid biomarker distributions in the catchment and sediments of a crater lake in central India JF - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry N2 - The basin-scale spatial variability in lipid biomarker proxies in lacustrine sediments, which are established tools for studying continental environmental change, has rarely been examined. It is often implicitly assumed that a lake sediment core provides an average integral of catchment sources. Here we evaluated the distribution of lipid biomarkers in a modern ecosystem and compared it with the sedimentary record. We analyzed lipid biomarkers in terrestrial and aquatic organisms and in lake surface sediments from 17 locations within the saline-alkaline Lonar crater lake in central India. Terrestrial vegetation and lake surface sediments were characterized by relatively high average chain length (ACL) index values (29.6-32.8) of leaf wax n-alkanes, consistent with suggestions that plants in drier and warmer climates produce longer chain alkyl lipids than plants in cooler and humid areas. A heterogeneous spatial distribution of ACL values in lake surface sediments was found: at locations away from the shore, the values were highest (31 or more), possibly indicating different sources and/or transport of terrestrial biomarkers. In floating, benthic microbial mats and surface sediment, n-heptadecane, carotenoids, diploptene, phytol and tetrahymanol occurred in large amounts. Interestingly, these biomarkers of a unique bacterial community were found in substantially higher concentrations in nearshore sediment samples. We suggest that human influence and subsequent nutrient supply resulted in increased primary productivity, leading to an unusually high concentration of tetrahymanol in the nearshore sediments. In summary, the data showed that substantial heterogeneity existed within the lake, but leaf wax n-alkanes in a core from the center of the lake represented an integral of catchment conditions. However, lake level fluctuation may potentially affect aquatic lipid biomarker distributions in lacustrine sediments, in addition to source changes. Y1 - 2014 U6 - https://doi.org/10.1016/j.orggeochem.2013.11.009 SN - 0146-6380 VL - 66 SP - 125 EP - 136 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ballato, Paolo A1 - Strecker, Manfred T1 - Assessing tectonic and climatic causal mechanisms in foreland-basin stratal architecture: insights from the Alborz Mountains, northern Iran JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - The southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3-km-thick sequence of Miocene sedimentary rocks, constituting three basin-wde coarsening-upward units spanning a period of 10(6)years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment-provenance data to characterize the relationships between tectonically-generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S>1, typical of each basal unit (17.5-16.0, 13.8-13.1 and 10.3-9.6Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S<1 (13.8 and 13.8-11Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra-basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S<1, at 11-10.3Ma and 9-6-7.6Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically-induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. KW - sediment supply KW - climatic and tectonic forcing KW - accommodation-space KW - sediment-supply ratio (A /S) KW - foreland-basin stratigraphy KW - Alborz Mountains Y1 - 2014 U6 - https://doi.org/10.1002/esp.3480 SN - 0197-9337 SN - 1096-9837 VL - 39 IS - 1 SP - 110 EP - 125 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Baroni, Gabriele A1 - Tarantola, S. T1 - A general probabilistic framework for uncertainty and global sensitivity analysis of deterministic models: A hydrological case study JF - Environmental modelling & software with environment data news N2 - The present study proposes a General Probabilistic Framework (GPF) for uncertainty and global sensitivity analysis of deterministic models in which, in addition to scalar inputs, non-scalar and correlated inputs can be considered as well. The analysis is conducted with the variance-based approach of Sobol/Saltelli where first and total sensitivity indices are estimated. The results of the framework can be used in a loop for model improvement, parameter estimation or model simplification. The framework is applied to SWAP, a 113 hydrological model for the transport of water, solutes and heat in unsaturated and saturated soils. The sources of uncertainty are grouped in five main classes: model structure (soil discretization), input (weather data), time-varying (crop) parameters, scalar parameters (soil properties) and observations (measured soil moisture). For each source of uncertainty, different realizations are created based on direct monitoring activities. Uncertainty of evapotranspiration, soil moisture in the root zone and bottom fluxes below the root zone are considered in the analysis. The results show that the sources of uncertainty are different for each output considered and it is necessary to consider multiple output variables for a proper assessment of the model. Improvements on the performance of the model can be achieved reducing the uncertainty in the observations, in the soil parameters and in the weather data. Overall, the study shows the capability of the GPF to quantify the relative contribution of the different sources of uncertainty and to identify the priorities required to improve the performance of the model. The proposed framework can be extended to a wide variety of modelling applications, also when direct measurements of model output are not available. KW - Global sensitivity analysis KW - Non-scalar input factors KW - Hydrological model KW - Multi-variables Y1 - 2014 U6 - https://doi.org/10.1016/j.envsoft.2013.09.022 SN - 1364-8152 SN - 1873-6726 VL - 51 SP - 26 EP - 34 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Leunert, Franziska A1 - Eckert, Werner A1 - Paul, Andrea A1 - Gerhardt, Volkmar A1 - Grossart, Hans-Peter T1 - Phytoplankton response to UV-generated hydrogen peroxide from natural organic matter JF - Journal of plankton research N2 - In aquatic systems, natural organic matter (NOM) and in particular humic substances effectively absorb the ultraviolet (UV)/visible light spectrum of solar radiation and act as a photoprotective filter for organisms. Simultaneously, UV contributes to the generation of potentially harmful reactive oxygen species (ROS). Dose-response experiments were conducted on cyanobacteria and green algae with hydrogen peroxide (H2O2) as a long-lived representative of ROS. Delayed fluorescence (DF) decay kinetics was used as a non-invasive tool to follow changes of phytoplankton activity in real time. In order to investigate phototoxicity and photoprotection by NOM on phytoplankton, we exposed algae to UV-pre-irradiated NOM and direct UV excitation. Cyanobacteria responded to H2O2 concentrations as low as 10(-7) M, while green algae were 2 orders of magnitude less sensitive. UV irradiation of medium with NOM generated H2O2 concentrations of 1.5 x 10(-7) to 3.6 x 10(-7) M. When exposed to these concentrations, only the DF of cyanobacteria led to a measurable effect while that of green algae did not change. The addition of NOM protected all phytoplankton from direct UV irradiation, but cyanobacteria benefitted less. From this we conclude that UV-irradiated water enriched with NOM can adversely affect the physiology of cyanobacteria, but not of green algae, which might control phytoplankton composition and species-specific activities. KW - reactive oxygen species KW - Microcystis aeruginosa KW - green algae KW - delayed fluorescence KW - phycocyanin Y1 - 2014 U6 - https://doi.org/10.1093/plankt/fbt096 SN - 0142-7873 SN - 1464-3774 VL - 36 IS - 1 SP - 185 EP - 197 PB - Oxford Univ. Press CY - Oxford ER - TY - INPR A1 - Thieken, Annegret A1 - Mariani, S. A1 - Longfield, S. A1 - Vanneuville, W. T1 - Preface: Flood resilient communities - managing the consequences of flooding T2 - Natural hazards and earth system sciences Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-33-2014 SN - 1561-8633 VL - 14 IS - 1 SP - 33 EP - 39 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Uhlemann, Steffi A1 - Thieken, Annegret A1 - Merz, Bruno T1 - A quality assessment framework for natural hazard event documentation: application to trans-basin flood reports in Germany JF - Natural hazards and earth system sciences Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-189-2014 SN - 1561-8633 VL - 14 IS - 2 SP - 189 EP - 208 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Nishihara, Yu A1 - Ohuchi, Tomohiro A1 - Kawazoe, Takaaki A1 - Spengler, Dirk A1 - Tasaka, Miki A1 - Kikegawa, Takumi A1 - Suzuki, Akio A1 - Ohtani, Eiji T1 - Rheology of fine-grained forsterite aggregate at deep upper mantle conditions JF - Journal of geophysical research : Solid earth KW - high-pressure KW - olivine KW - rheology KW - upper mantle Y1 - 2014 U6 - https://doi.org/10.1002/2013JB010473 SN - 2169-9313 SN - 2169-9356 VL - 119 IS - 1 SP - 253 EP - 273 PB - American Geophysical Union CY - Washington ER -