Über das spätglaziale Klima in Finnland

Ohne Zusammenfassung     

Fossile Riffe als Klimazeugen

Ohne Zusammenfassung     

Climate change adaptation of coffee production in space and time

Savannas constitute the most fire-prone vegetation type on earth and are a significant source of greenhouse gas emissions. Most savanna fires are lit by people for a variety of livelihood applications. ‘Savanna burning’ is an accountable activity under the Kyoto Protocol, but only Australia, as a developed economy, accounts for emissions from this source in its national accounts. Over the past decade considerable effort has been given to developing savanna burning projects in northern Australia, combining customary indigenous (Aboriginal) approaches to landscape-scale fire management with development of scientifically robust emissions accounting methodologies. Formal acceptance by the Australian Government of that methodology, and its inclusion in Australia’s developing emissions trading scheme, paves the way for Aboriginal people to commercially benefit from savanna burning projects. The paper first describes this Australian experience, and then explores options for implementing community-based savanna burning emissions reduction projects in other continental savanna settings, specifically in Namibia and Venezuela. These latter examples illustrate that savanna fire management approaches potentially have broader application for contributing to livelihood opportunities in other fire-prone savanna regions.     

8000-year history of palaeoproductivity in a large boreal lake

An 8000-year record of palaeoproductivity, based on the chemical and chironomid stratigraphies from Lake Päijänne, S. Finland, was assessed with respect to known morphometric, climatic and anthropogenic events. A gradual trend of dystrophication and an associated decrease in aquatic production was detected during the Holocene, with the following exceptions: (1) high diatom and chironomid production around 8000-6000 cal yr BP, (2) eutrophication around 2000 cal yr BP, and (3) an anthropogenic signal during the last few decades.The changes in chironomid assemblages, before the past few decades, have mainly been shifts in concentration, but not in species composition. Variation in chironomid production was mainly explained by the accumulations of biogenic silicon, carbon and organic matter. Nutrient availability seems to be important in controlling biogenic silicon, which we use to infer past diatom production. The high production ca. 8000-6000 cal yr BP and the fluctuation in chironomid influx after ca. 2000 cal yr BP, however, were probably caused by the proposed warm/dry and cold/wet conditions during these times, respectively. These results highlight the sensitivity of boreal shield lake ecosystems to climatic forcing. In contrast, the pronounced change in the morphometry of the basin around 7000 cal yr BP had little effect on the trophic state of the lake. The human-induced trophic change during the past few decades has affected the Lake Päijänne ecosystem to an extent never experienced before during the last 8000-years.     

Impact of Climate Change on Hydrological Regimes and Water Resources Management in the Rhine Basin

The International Commission for the Hydrology of the Rhine basin (CHR) hascarried out a researchproject to assess the impact of climate change on the river flow conditionsin the Rhine basin. Along abottom-up line, different detailed hydrological models with hourly and dailytime steps have beendeveloped for representative sub-catchments of the Rhine basin. Along atop-down line, a water balancemodel for the entire Rhine basin has been developed, which calculates monthlydischarges and which wastested on the scale of the major tributaries of the Rhine. Using this set ofmodels, the effects of climatechange on the discharge regime in different parts of the Rhine basin werecalculated using the results ofUKHI and XCCC GCM-experiments. All models indicate the same trends in thechanges: higher winterdischarge as a result of intensified snow-melt and increased winterprecipitation, and lower summerdischarge due to the reduced winter snow storage and an increase ofevapotranspiration. When the resultsare considered in more detail, however, several differences show up. These canfirstly be attributed todifferent physical characteristics of the studied areas, but different spatialand temporal scales used in themodelling and different representations of several hydrological processes(e.g., evapotranspiration,snow melt) are responsible for the differences found as well. Climate changecan affect various socio-economicsectors. Higher temperatures may threaten winter tourism in the lower wintersport areas. The hydrologicalchanges will increase flood risk during winter, whilst low flows during summerwill adversely affectinland navigation, and reduce water availability for agriculture and industry.Balancing the required actionsagainst economic cost and the existing uncertainties in the climate changescenarios, a policy of `no-regretand flexibility' in water management planning and design is recommended, whereanticipatory adaptivemeasures in response to climate change impacts are undertaken in combinationwith ongoing activities.     

Detrital chromites in metasediments of the East-Arabian continental margin in the Saih Hatat area: constraints for the palaeogeographic setting of the Hawasina and Semail basins (Oman Mountains)

 In Oman, the convergence between Arabia and Eurasia resulted in the Late Cretaceous overthrusting of oceanic crust and mantle lithosphere onto the Arabian continental margin. During this compressional event, a part of the continental plate was subducted to a depth of more than 60 km (0.5 GPa, 250–350  °C to more than 2.0 GPa, 550  °C) resulting in progressive metamorphism of the continental margin sediments, well exposed in the Saih Hatat tectonic window, northeastern Oman Mountains. We attempt to constrain the possibility of one continuous history of extension (starting along the east Arabian continental margin in the Permian) that was followed by one continuous history of convergence starting at 90 Ma near a dead oceanic ridge. This compression resulted in the observed progressive metamorphism by ophiolite overthrusting onto the continental margin. Constraining arguments are the palaeogeographic setting before ophiolite obduction of the As Sifah units and the Hawasina Complex near Ghurba. Detrital chromites in the Triassic–Cretaceous metasediments of the Hawasina Complex are compared with magmatic Semail chromites, and the whole-rock chemistry of these metasediments and associated metabasites are investigated. In contrast to former hypotheses, differences in the chemical composition between detrital and magmatic chromites, and the probable origin of all detrital chromites in the Hawasina Basin from Permian age oceanic rocks, suggest that the high-pressure metamorphic sediments of As Sifah can be considered as part of the basal deposits of the Hawasina Basin. Received: 1 September 1998 / Accepted: 18 January 1999     

A geo-environmental map for the sustainable development of the Kathmandu Valley, Nepal

An engineering and environmental geological map of the Kathmandu Valley in Nepal has been elaborated within a project of German-Nepalese cooperation. In the Kathmandu Valley, the major geo-environmental problems arise from haphazard exploitation of geologic resources, local landslide zones, severe problems of garbage disposal, river flooding and a dramatic river pollution. The map was prepared by the use of GIS techniques. It contains all basic geological and environmental data, as geotechnical risk zones (landslide-prone areas or those of poor foundation conditions), areas for preferable extraction of construction material and those not to be allowed to be exploited, areas of immediate need of reforestation in order to prevent landslide or badland development, groundwater protection zones, and suitable garbage disposal sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

The contribution of scattering to near-surface attenuation

The rapid decrease of the acceleration spectral amplitude at high frequencies has widely been modeled by the spectral decay factor kappa (κ). Usually, the path-corrected component of κ, often called κ₀, is believed to be a local and frequency-independent site characteristic, in turn representing attenuation related to waves propagating vertically through the very shallow layers beneath the study site. Despite the known relevance of κ₀ in a wide range of seismological applications, most methods for its calculation do not fully consider the influence of the scattering component. To account for the scattering component, we present a summary of statistical observations of the seismic wavefield at sites of the Swiss seismic networks. The intrinsic properties of the wavefield show a clear dependency on the local shallow subsoil conditions with differences in the structural heterogeneity of the shallow subsoil layers producing different scattering regimes. Such deviations from the ballistic behavior (i.e., direct waves that sample only distinct directions) are indicative for local structural heterogeneities and the associated level of scatter. Albeit the attenuation term related to scattering depends nonlinearly on the intrinsic term, the results indicate that the commonly used explanation for the high-frequency decay spectrum might not be appropriate but involving the amount of scattering might allow better constrained estimates of κ₀.     

Estimating the sediment trap efficiency of intermittently dry reservoirs: lessons from the Kruger National Park,South Africa

The assessment of sediment yield from reservoir siltation requires knowledge of the reservoir's sediment trap efficiency (TE). Widely used approaches for the estimation of the long‐term mean TE rely on the ratio of the reservoir's storage capacity (C) to its catchment size (A) or mean annual inflow (I). These approaches have been developed from a limited number of reservoirs (N ≤ 40), most of them located in temperate climate regions. Their general applicability to reservoirs receiving highly variable runoff such as in semi‐arid areas has been questioned. Here, we examine the effect of ephemeral inflow on the TE of 10 small (≤ 280 × 10³ m³), intermittently dry reservoirs located in the Kruger National Park. Fieldwork was conducted to determine the storage capacity of the reservoir basins. The frequency and magnitude of spillage events was simulated with the daily time step Pitman rainfall–runoff model. Different runoff scenarios were established to cope with uncertainties arising from the lack of runoff records and imperfect input data. Scenarios for the relationship between water and sediment discharge were created based on sediment rating curves. Taking into account uncertainties in hydrological modelling, uncertainties of mean TE estimates, calculated from all scenarios (N = 9), are moderate, ranging from ±6 to ±11% at the 95% confidence level. By comparison, estimating TE from the storage capacity to catchment area (C/A) ratio induces high uncertainty (ranges of 35 to 65%), but this uncertainty can be confined (15 to 33%) when the latter approach is combined with hydrological modelling. Established methods relying on the storage capacity to mean annual inflow (C/I) ratio most probably lead to an overestimation of the TE for the investigated reservoirs. The approach presented here may be used instead to estimate the TE of small, intermittently dry reservoirs in semi‐arid climate regions. Copyright © 2017 John Wiley & Sons, Ltd.