Elevated nutrient inputs challenge the health and functioning of aquatic ecosystems. To improve riverine water quality management, it is necessary to understand the underlying biogeochemical and ...physical processes, anthropogenic drivers and their interactions at catchment scale. We hypothesize that the spatial heterogeneity of nutrient sources dominantly controls the variability of in‐stream concentration dynamics among catchments. We investigated controls of mean nitrate (NO3−), phosphate (PO43−), and total organic carbon (TOC) concentrations and concentration‐discharge (C‐Q) relationships in 787 German catchments of a newly assembled data base, covering a wide range of physiographic and anthropogenic settings. We linked water quality metrics to catchment characteristics using partial least squares regressions and random forests. We found archetypal C‐Q patterns with enrichment dominating NO3− and TOC, and dilution dominating PO43− export. Both the mean NO3− concentrations and their variance among sites increased with agricultural land use. We argue that subsurface denitrification can buffer high nitrogen inputs and cause a decline in concentration with depth, resulting in chemodynamic, strongly positive C‐Q patterns. Mean PO43− concentrations were related to point sources, though the low predictive power suggests effects of unaccounted in‐stream processes. In contrast, high diffuse agricultural inputs explained observed positive PO43− C‐Q patterns. TOC levels were positively linked to the abundance of riparian wetlands, while hydrological descriptors were important for explaining TOC dynamics. Our study shows a strong modulation of anthropogenic inputs by natural controls for NO3− and PO43− concentrations and dynamics, while for TOC only natural controls dominate observed patterns across Germany.
Plain Language Summary
Phosphorus, nitrogen, and organic carbon are key elements of plants and all living organisms. Humans are altering the nutrient cycles especially, to improve agricultural productivity and through domestic and industrial wastewater. Excess nutrients in surface waters have harmed many aquatic ecosystems by causing toxic algal blooms and a loss of biodiversity. Low nutrient concentrations and habitat variability are similarly important to those ecosystems, but human interference with natural drivers is not yet fully understood. To better understand and disentangle natural or human controls, we investigated nutrient concentrations and their variability across German catchments with varying landscapes and anthropogenic conditions. The human impact is clearly visible for mean nitrate concentrations, while the (natural) subsurface properties mainly controlled the variability of riverine nitrate. In the past, phosphate inputs were usually linked to wastewater, yet we found the control of agricultural activities on concentration dynamics to be unexpectedly high. Organic carbon was mainly associated with natural sources related to riparian wetlands where interactions with other nutrients are possible. This understanding of dominant controls is important in order to adapt management strategies to ensure healthy aquatic ecosystems.
Key Points
Riverine NO3− dynamics are controlled by vertical concentration heterogeneity, which can result from subsurface denitrification
Diffuse P sources exert a strong control on the spatial variability of PO43− export patterns in contrast to point sources
Share of riparian wetlands controls the mean TOC concentrations in German catchments
Airborne Laser Bathymetry (ALB) is an attractive technology for the measurement of shallow water bodies because of the high acquisition rate and high point densities that can be achieved. Of special ...interest is the application of ALB in non-navigable areas where the only alternatives are conventional terrestrial surveying by wading with a pole, multi-media photogrammetry, or spectrally based depth retrieval. The challenge for laser based approaches in such very shallow waters (<2 m) is the difficulty of discriminating between echoes from the surface and the bottom. This work presents an algorithm for the detection of surface, volume, and bottom (SVB) designed to meet this challenge while requiring only a single wavelength (532nm) sensor. The accuracy of the algorithm is cross validated against reference measurements obtained from terrestrial survey with a total station and shows negligible bias and virtually no depth dependence for the experimental dataset.
Present-day disturbances are transforming European forest landscapes, and their legacies determine the vulnerability and resilience of the emergent forest generation. To understand these legacy ...effects, we investigated the resilience of the aboveground forest biomass (Babg) to a sequence of disturbances affecting the forest in different recovery phases from the initial large-scale impact. We used the model iLand to simulate windthrows that affected 13–24% of the Babg in a Central European forest landscape. An additional wind event was simulated 20, 40, 60, or 80 years after the initial impact (i.e., sequences of two windthrows were defined). Each windthrow triggered an outbreak of bark beetles that interacted with the recovery processes. We evaluated the resistance of the Babg to and recovery after the impact. Random Forest models were used to identify factors influencing resilience. We found that Babg resistance was the lowest 20 years after the initial impact when the increased proportion of emergent wind-exposed forest edges prevailed the disturbance-dampening effect of reduced biomass levels and increased landscape heterogeneity. This forest had a remarkably high recovery rate and reached the pre-disturbance Babg within 28 years. The forest exhibited a higher resistance and a slower recovery rate in the more advanced recovery phases, reaching the pre-disturbance Babg within 60–80 years. The recovery was enhanced by higher levels of alpha and beta diversity. Under elevated air temperature, the bark beetle outbreak triggered by windthrow delayed the recovery. However, the positive effect of increased temperature on forest productivity caused the recovery rate to be higher under the warming scenario than under the reference climate.
We conclude that resilience is not a static property, but its magnitude and drivers vary in time, depending on vegetation feedbacks, interactions between disturbances, and climate. Understanding these mechanisms is an essential step towards the operationalization of resilience-oriented stewardship.
Display omitted
•The effect of disturbance legacies on forest biomass resilience was investigated.•Resilience drivers differ depending on time after the previous disturbance.•Biomass resistance and the recovery rate are inversely related in the studied system.•The structure of disturbed forest landscapes should be actively exploited in anticipation of future impacts.
As the literature on small state foreign policy predicts that smaller states of the international community attempt to enlarge their influence by seeking a constructive status or proving their ...adherence to positive norms, the cases in which small states use a negative image to better their international position are almost completely neglected. The article aims to assess how the status of Visegrád countries in interstate society changed since their accession to the European Union in light of the generally negative perception of their governments’ ideological background connected to different kinds of populism and nationalism. Using the GDELT Database, the number of government-level interactions initiated towards the Czech Republic, Hungary, Poland, and Slovakia was analysed in a European context between 2004 and 2020. The results of the inquiry showed a drastic decrease in the interactions initiated towards the four countries between 2004 and the mid-2010s with a slightly higher ratio of confrontative interactions than in the case of other small and middle-sized states. Data show that Hungary, governed by populist parties since 2010, witnessed the smallest drop in attention in the last decade. These results defy the expectations of the small state literature and suggest a more complicated relationship between international status and the image of small states.
Groundwater discharge in alpine headwaters sustains baseflow in rivers originating in mountain ranges of the world, which is critically important for aquatic habitats, run‐of‐river hydropower ...generation, and downstream water supply. Groundwater storage in alpine watersheds was long considered negligible, but recent field‐based studies have shown that aquifers are ubiquitous in the alpine zone with no soil and vegetation. Talus, moraine, and rock glacier aquifers are common in many alpine regions of the world, although bedrock aquifers occur in some geological settings. Alpine aquifers consisting of coarse sediments have a fast recession of discharge after the recharge season (e.g., snowmelt) or rainfall events, followed by a slow recession that sustains discharge over a long period. The two‐phase recession is likely controlled by the internal structure of the aquifers. Spatial extent and distribution of individual aquifers determine the groundwater storage‐discharge characteristics in first‐ and second‐order watersheds in the alpine zone, which in turn govern baseflow characteristics in major rivers. Similar alpine landforms appear to have similar hydrogeological characteristics in many mountain ranges across the world, suggesting that a common conceptual framework can be used to understand alpine aquifers based on geological and geomorphological settings. Such a framework will be useful for parameterizing storage‐discharge characteristics in large river hydrological models.
Article Impact Statement: This article presents a synthesis of current knowledge on alpine groundwater providing critical baseflow to major rivers of the world.
The streamflow drought hazard can be characterized in a variety of ways, including using different indices. Traditionally, percentile‐based indices, such as Q95 (the flow exceeded 95% of time), have ...been used by the hydrological community. Recently, the use of anomaly indices such as the Standardized Streamflow Index (SSI), a probability index‐based approach adopted from the climatological community, has increased in popularity. The SSI can be calculated based on various (non)parametric methods. Up to now, there is no consensus which method to use. This study aims to raise awareness how the inherent sensitivity of the SSI to the used method influences derived drought characteristics. We compared SSI time series computed with seven different probability distributions and two fitting methods as well as with different nonparametric methods for 369 rivers across Europe. Results showed that SSI time series and associated drought characteristics are indeed sensitive to the method of choice. A resampling experiment demonstrated the sensitivity of the parametric SSI to properties of both the low and high end of the sample. Such sensitivities might hinder a fair comparison of drought in space and time and highlight the need for a clear recommendation which method to use. We could recommend overall suitable methods, for example, from the parametric approaches, the Tweedie distribution has several advantageous properties such as a low rejection rate (2%) and a lower bound at zero. However, the most suitable method depends on the used evaluation criteria. Rather, we stress that shown approach‐specific sensitivities and uncertainties should be carefully considered.
Key Points
The Standardized Streamflow Index (SSI) is a probability‐based index used to express the streamflow drought hazard as an anomaly
We show a sensitivity of drought characteristics to the method used to derive the SSI as well as to low‐ and high‐end sample properties
We evaluate the suitability of different methods to derive the SSI and discuss implications for drought assessments and operational use
Extending from Northern America to Central China the Variscan belt is a Paleozoic Orogen exceptionally well endowed in magmatic-hydrothermal ore deposits, including skarn deposits. Yet, the genesis ...of fertile skarns and their distinction from barren equivalents in orogenic zones is only poorly constrained. Here, we present innovative U-Pb laser-ablation inductively-coupled-plasma mass-spectrometry geochronology of garnet from different skarns in the Erzgebirge, a classic metallogenic province in central Europe. Garnet ages obtained not only constrain the timing of fertile skarn formation and associated Sn, W, Fe, Zn, Cu and In mineralization, but also clearly distinguish these from barren skarn bodies. We show that barren skarns formed during times of peak regional metamorphism at ∼340 Ma whereas mineralized skarns are temporally associated with late-orogenic magmatism at ∼325-313 Ma as well as post-orogenic magmatism at ∼308-295 Ma. The recognition of discrete mineralization events associated with the largest and economically most important skarn deposits provides valuable insight into the punctuated evolution of magmatic-hydrothermal systems in ancient collisional orogens on a regional scale; this has important implications to direct future mineral exploration.
•Origin and genesis of skarns in orogenic zones.•Geodynamic evolution of hydrothermal mineral systems in orogenic belts.•Innovative U-Pb LA-ICP-MS geochronology of garnet.•Implications for exploration targeting.
Elites should be regarded and approached as gregarious social entities (groups, networks) rather than as outstanding individuals.The volume aims to explore the elites in East-Central and ...South-Eastern Europe during the long nineteenth century from the perspective of their gregarious tendencies (i.e., groupness), to assess the role of the latter in the elite’s decisions and agenda, and to observe the transformations brought in this regard by the changing social and political landscape.While the gregarious tendencies of the members of the elite were rooted in their shared perspectives, in their mutual interests or in the communion of cultural patterns, it is clear that during the process of group formation, kinship ties played an unassailable part, although they were likely never a causal factor.The volume covers the research on elites from the early 18th century to the interwar period, focussing on the Banat, Bessarabia, Bohemia, Bulgaria, Dalmatia, Hungary, Rumania, Serbia, Slovenia, as well as looking into Austria and Austria-Hungary in total.
PDF
