ALBERT

Description: This paper presents radon flux profiles from four regions in Schleswig–Holstein (Northern Germany). Three of these regions are located over deep-rooted tectonic faults or salt diapirs and one is in an area without any tectonic or halokinetic activity, but with steep topography. Contrary to recently published studies on spatial patterns of soil radon gas concentration we measured flux of radon from soil into the atmosphere. All radon devices of each profile were deployed simultaneously to avoid inconsistencies due to strong diurnal variations of radon exhalation. To compare data from different seasons, values had to be normalized. Observed radon flux patterns are apparently related to the mineralogical composition of the Quaternary strata (particularly to the abundance of reddish granite and porphyry), and its grain size (with a flux maximum in well-sorted sand/silt). Minimum radon flux occurs above non-permeable, clay-rich soil layers. Small amounts of water content in the pore space increase radon flux, whereas excessive water content lessens it. Peak flux values, however, are observed over a deep-rooted fault system on the eastern side of Lake Plön, i.e., at the boundary of the Eastholstein Platform and the Eastholstein Trough. Furthermore, high radon flux values are observed in two regions associated with salt diapirism and near-surface halokinetic faults. These regions show frequent local radon flux maxima, which indicate that the uppermost strata above salt diapirs are very inhomogeneous. Deep-rooted increased permeability (effective radon flux depth) or just the boundaries between permeable and impermeable strata appear to concentrate radon flux. In summary, our radon flux profiles are in accordance with the published evidence of low radon concentrations in the “normal” soils of Schleswig–Holstein. However, very high values of radon flux are likely to occur at distinct locations near salt diapirism at depth, boundaries between permeable and impermeable strata, and finally at the tectonically active flanks of the North German Basin.

Description: Bundesministerium für Wirtschaft und Energie http://dx.doi.org/10.13039/501100006360

Description: Johannes Gutenberg-Universität Mainz (1030)

Description: This paper develops a method to explore how alternative scenarios of the expansion of maize production for biogas generation affect biodiversity and ecosystem services (ES). Our approach consists of four steps: (i) defining scenario targets and implementation of assumptions; (ii) simulating crop distributions across the landscape; (iii) assessing the ES impacts; and (iv) quantifying the impacts for a comparative trade-off analysis. The case study is the region of Hannover, Germany. One scenario assumes an increase of maize production in a little regulated governance system; two others reflect an increase of biogas production with either strict or flexible environmental regulation. We consider biodiversity and three ES: biogas generation, food production and the visual landscape. Our results show that the expansion of maize production results in predominantly negative impacts for other ES. However, positive effects can also be identified, i.e., when the introduction of maize leads to higher local crop diversity and, thus, a more attractive visual landscape. The scenario of little regulation portrays more negative impacts than the other scenarios. Targeted spatial planning, implementation and appropriate governance for steering maize production into less sensitive areas is crucial for minimizing trade-offs and exploiting synergies between bioenergy and other ES.

Description: During the last ice age, the Northern Hemisphere experienced a series of abrupt millennial-scale climatic changes linked to variations in the strength of the Atlantic Meridional Overturning Circulation and sea-ice extent. However, our understanding of their impacts on decadal-scale climate variability in central Europe has been limited by the lack of high-resolution continental archives. Here, we present a near annual-resolution climate proxy record of central European temperature reconstructed from the Eifel maar lakes of Holzmaar and Auel in Germany, spanning the past 60,000 years. The lake sediments reveal a series of previously undocumented multidecadal climate cycles of around 20 to 150 years that persisted through the last glacial cycle. The periodicity of these cycles suggests that they are related to the Atlantic multidecadal climate oscillations found in the instrumental record and in other climate archives during the Holocene. Our record shows that multidecadal variability in central Europe was strong during all warm interstadials, but was substantially muted during all cold stadial periods. We suggest that this decrease in multidecadal variability was the result of the atmospheric circulation changes associated with the weakening of the Atlantic Meridional Overturning Circulation and the expansion of North Atlantic sea-ice cover during the coldest parts of the last ice age.

Description: Here, we present a near-annual-resolution climate proxy record of central European temperature reconstructed from the Eifel maar lakes of Holzmaar and Auel in Germany spanning the past 60,000 years. The lake sediments reveal a series of previously undocumented multidecadal climate cycles of around 20- to 150-years that persisted through the last glacial cycle. The periodicity of these cycles suggests that they are related to the Atlantic multidecadal climate oscillations found in the instrumental record and in other climate archives during the Holocene. Our record shows that multidecadal variability in central Europe was strong during all warm interstadials, but was substantially muted during all cold stadial periods. We suggest that this decrease in multidecadal variability was the result of the atmospheric circulation changes associated with the weakening of the AMOC and the expansion of North Atlantic sea ice cover during the coldest parts of the last ice age. Organic carbon was determined by measuring the reflectance for each wavelength of the visible light as percent relative to a white color standard. Absorption forms a pronounced minimum in the wavelength range of 640 nm – 730 nm in cores both from Holzmaar and Auel. Reflectivity in this wavelength band (I-Band, 660 – 670 nm, i.e. the red part of the spectrum), was shown to relate to sediment concentrations of chlorophyll a and its degradation products.The absorption at 670 nm was calibrated in the first study versus organic carbon and chlorine content, both of which revealed a significant relation to the “In situ Reflectance Spectroscopy – ISRS” absorption at 670 nm, which is subtracted from the interpolated value between 640 and 730 nm. The ISRS670 detects accordingly chlorophyll a, b, and c and also Bacteriochlorophyll c and d (Green sulfur bacteria) as well as their derivates and can be applied to detect trends in total aquatic paleoproduction in both ocean and lake sediments.

Description: Laminated sediment records from several maar lakes and dry maar lakes of the Eifel (Germany) reveal the history of climate, weather, environment, vegetation, and land use in central Europe during the last 60,000 years. The time series of the last 30,000 years is based on a continuous varve counted chronology, the MIS3 section is tuned to the Greenland ice - both with independent age control from 14C dates. Total carbon, pollen and plant macrofossils are used to synthesize a vegetation-stack, which is used together with the stacks from seasonal varve formation, flood layers, eolian dust content and volcanic tephra layers to define Landscape Evolution Zones (LEZ). LEZ 1 encompasses the landscape dynamics of the last 6000 years with widespread human influence. The natural oak and hazel forests of the early Holocene back to 10,500 b2k define LEZ 2. LEZ 3, the late glacial between 10,500 and 14,700 b2k, shows the development of a boreal forest with abundant grass and shallow water biomass in the lakes. The maximum of the last glaciation (LEZ 4: 14,700-23,000 b2k) was characterized by sparse vegetation of moss and characeae. These sediments are generally devoid of clay and sand and reveal no indication of snow-meltwater events. Accordingly, the Last Glacial Maximum (LGM) must have been extremely arid in central Europe. The sediments of the subsequent LEZ 5 from 23,000-28,500 b2k preserve distinct layers of clay and coarse sand, which indicates running water with clay in suspension and ephemeral coarse-grained fluvial sediment discharge. Abundant Ranunculaceae macroremains (used for 14C dating), insects, moss and fungi sclerotia reflect a tundra environment during a time of frequent strong snowmelt events. Total carbon content, Betula-Pinus pollen and diatoms reach increased concentrations during Marine Isotope Stage (MIS) 3 interstadials that occurred between 28,500 and 36,500 b2k (LEZ 6). The entire MIS3 interstadials are well documented in the organic carbon record from the Auel dry maar. The main paleobotanical indicators of MIS3 are, however, grass pollen and heliophytes, which indicate a steppe environment with scattered/patchy trees during the interstadials. The stadial phases inferred during LEZ 6 reveal initiation of eolian dust deflation. The change of the early MIS 3 forested landscape to a steppe occurred with the LEZ 7-LEZ 6 transition. This is when modern man spread in central Europe. The principle vegetation change to a steppe at 36,500 b2k must have favoured the spread of horses, an important hunting prey of modern humans. We propose accordingly that the migration of the modern humans into central Europe might have been at least partly driven by climate and associated vegetation change. The LEZ 7 encompassed the time interval 36,500 to 49,000 b2k and was characterized by a boreal forest with high abundance of pine, birch, as well as spruce during the interstadial events. Abundant charcoal fragments indicate that this taiga was under frequent drought stress with regular burning. The most unexpected finding, but corroborated by all our maar records is the dominance of thermophilous tree taxa from 49,000 to 55,000 b2k (LEZ 8). Greenland interstadials 13 and 14 were apparently the warmest of MIS 3 according to the Eifel pollen records. The preceeding LEZ 9 from 55,000 to 60,000 b2k is also dominated by spruce, but thermophilous trees were sparse. A warm early MIS3 appears plausible, because summer insolation (at 60° N) was higher in the early MIS 3 than today, ice cover was low in Scandinavia and sea-surface temperatures of the North Atlantic were almost comparable to modern values during GI-14.

Description: This study reconstructs the main flood phases in central Europe from event layers in sediment cores from Holocene Eifel maar lakes and Pleistocene dry maar structures. These reconstructions are combined with recent gauge time-series to cover the entire precipitation extremes of the last 60 000 years. In general, Eifel maar sediments are perfectly suited for the preservation of event layers since the deep water in the maar lakes is seasonal anoxic and therefore, bioturbation is low. However, the preservation of annual lamination is only preserved in Holzmaar and Ulmener Maar; the other cores are dated by 14C, magnetostratigraphy, tephra markers and ice core tuning. The cores were drilled in the Eifel region of central western Germany, which represents a climatic homogenous region from Belgium to Poland and all across Central Europe. A total of 233 flood layers over 7.5 mm were detected in all analysed cores. The stratigraphic classification of the flood events follows the newly defined Landscape Evolution Zones (LEZ). The strongest events in the Holocene have occurred during LEZ 1 (0?6000 b2k) in the years 658, 2800 and 4100 b2k. Flood layers in the LEZ 2 (6000-10 500 b2k) are not as frequent as during the LEZ 1, nevertheless, the floods cluster between 6000 and 6500 b2k. Twenty flood layers are found in the LEZ 3 (10 500?14 700 b2k); 11 in LEZ 4 (14 700-21 000 b2k); 15 in LEZ 5 (21 000-28 500 b2k); 34 in LEZ 6 (28 500?36 500 b2k); 8 in LEZ 7 (36 500-49 000 b2k); zero in LEZ 8 (49 000-55 000 b2k) and LEZ 9 (55 000-60 000 b2k). The maximum flood phases during the Pleistocene are at 11 500-17 500 (late glacial and Younger Dryas), 23 000-24 000 (before Greenland Interstadial (GI) 2), 29 000-35 000 (especially between GI 5 and 4) and 44 000-44 500 b2k (transition from GI 12 to 11). The variations in flood dynamics are climatically driven and mainly associated with climate transitions and colder periods, combined with light vegetation. It turns out that low vegetation coverage related to both Greenland Stadial phases and anthropogenic impacts since late Holocene is the main cause for the development of flood layers in maar sediments. The precipitation itself, plays only a secondary role. This interpretation is based on the current climate understanding of cold phases and several studies of fluvial erosion related to vegetation coverage.