Structural and functional shifts in zoobenthos induced by organic enrichment — Implications for community recovery potential

Habitat change induced by organic enrichment is a growing concern for the sustainability of benthic communities in coastal aquatic environments. This case study describes the spatial and temporal response patterns and the recovery potential of low-diversity benthic communities to organic enrichment at two fish farm locations, during the rearing periods (15 and 20 years, respectively) and the following recovery periods (2 years). The spatial extent of disturbance differed depending on the hydromorphological characteristics of the rearing sites, but degraded macrobenthic communities close to both fish farms were recorded soon after the activity started. Continued organic enrichment resulted in high species turnover-rates and in an altered benthic community composition at both locations. After fish farm abatement, a partial recovery was detected in species richness, but abundance and biomass values were reduced and changes in structural composition remained. Alterations in benthic biological traits were observed at both fish farm locations, implying that organic enrichment might cause changes in benthic community function within low-diversity benthic communities.     

Adaptive management to climate change for Norway spruce forests along a regional gradient in Finland

We hypothesized that the responses of boreal Norway spruce (Picea abies) forests to climate change would be region-specific due to regional differences in temperature and water availability. In this context, we analyzed the adaptive effects of varied thinning intensities on the gross primary production (GPP), total stem wood growth, and timber yield over a 100-year period using a process-based ecosystem model. Our simulations represented Norway spruce forests for five different bioclimatic zones spanning southern to northern Finland (61–67^oN). Ten thinning regimes with thinning intensities ranging from 5 to 50 %, as well as an unthinned regime, were included in the calculations. The results showed that at the southern sites without thinning, the cumulative GPP and total stem wood growth were lower under the changing climate than in the current climate over the simulation period due to greater water depletion via evapotranspiration and reduced soil water availability. At the central and the northern sites, the climate changes increasingly enhanced the GPP and total stem wood growth due to the mitigation of low-temperature limitation and the improved soil water availability. Thinning generally mitigated the soil water deficit by reducing water evaporation and led to a reduction of the natural mortality. At the southern sites, light and moderate thinning intensities increased the GPP and total stem wood growth relative to sites with a changing climate that experienced no thinning. Moreover, moderate thinning resulted in the greatest timber yield. Heavy thinning, in which a large proportion of standing trees were removed, reduced the GPP and total stem wood growth despite allowing increased soil water availability. At the northern sites, all levels of thinning, including light thinning, decreased the GPP and stem wood growth, indicating that soil water availability was not a limiting factor for growth prior to thinning.     

Modelling multiphase chemistry in deliquescent aerosols and clouds using CAPRAM3.0i

Modelling studies were performed with the multiphase mechanism RACM-MIM2ext/CAPRAM 3.0i to investigate the tropospheric multiphase chemistry in deliquesced particles and non-precipitating clouds using the SPACCIM model framework. Simulations using a non-permanent cloud scenario were carried out for two different environmental conditions focusing on the multiphase chemistry of oxidants and other linked chemical subsystems. Model results were analysed by time-resolved reaction flux analyses allowing advanced interpretations. The model shows significant effects of multiphase chemical interactions on the tropospheric budget of gas-phase oxidants and organic compounds. In-cloud gas-phase OH radical concentration reductions of about 90 % and 75 % were modelled for urban and remote conditions, respectively. The reduced in-cloud gas-phase oxidation budget increases the tropospheric residence time of organic trace gases by up to about 30 %. Aqueous-phase oxidations of methylglyoxal and 1,4-butenedial were identified as important OH radical sinks under polluted conditions. The model revealed that the organic C₃ and C₄ chemistry contributes with about 38 %/48 % and 8 %/9 % considerably to the urban and remote cloud / aqueous particle OH sinks. Furthermore, the simulations clearly implicate the potential role of deliquescent particles to operate as a reactive chemical medium due to an efficient TMI/HO_x,y chemical processing including e.g. an effective in-situ formation of OH radicals. Considerable chemical differences between deliquescent particles and cloud droplets, e.g. a circa 2 times more efficient daytime iron processing in the urban deliquescent particles, were identified. The in-cloud oxidation of methylglyoxal and its oxidation products is identified as efficient sink for NO₃ radicals in the aqueous phase.     

Spatial gridding of daily maximum and minimum 2 m temperatures supported by satellite observations

The usefulness of two remotely sensed variables, land surface temperature (LST) and cloud cover (CC), as predictors for the gridding of daily maximum and minimum 2 m temperature (T _min/T _max) was assessed. Four similar gridding methods were compared, each of which applied regression kriging to capture the spatial variation explained by the predictors used; however, both methods differed in the interpolation steps performed and predictor combinations used. The robustness of the gridding methods was tested for daily observations in January and July in the period 2009–2011 and in two different regions: the Central European region (CER) and the Iberian Peninsula (IP). Moreover, the uncertainty estimate provided by each method was evaluated using cross-validation. The regression analyses for both regions demonstrated the high predictive skills of LST for T _min and T _max on daily and monthly timescales (and lower predictive skills of CC). The application of LST as a predictor considerably improved the gridding performance over the IP region in July; however, there was only a slight improvement over the CER region. CC reduced the loss of spatial variability in the interpolated daily T _min/T _max values over the IP region. The interpolation skill was mainly controlled by the station density, but also depended on the complexity of the terrain. LST was shown to be of particular value for very low station densities (1 station per 50,000 km²). Analyses with artificially decreasing station densities showed that even in the case of very low station densities, LST allows the determination of useful regression functions.     

High resolution regional climate model simulations for Germany: part I—validation

A five-member ensemble of regional climate model (RCM) simulations for Europe, with a high resolution nest over Germany, is analysed in a two-part paper: Part I (the current paper) presents the performance of the models for the control period, and Part II presents results for near future climate changes. Two different RCMs, CLM and WRF, were used to dynamically downscale simulations with the ECHAM5 and CCCma3 global climate models (GCMs), as well as the ERA40-reanalysis for validation purposes. Three realisations of ECHAM5 and one with CCCma3 were downscaled with CLM, and additionally one realisation of ECHAM5 with WRF. An approach of double nesting was used, first to an approximately 50 km resolution for entire Europe and then to a domain of approximately 7 km covering Germany and its near surroundings. Comparisons of the fine nest simulations are made to earlier high resolution simulations for the region with the RCM REMO for two ECHAM5 realisations. Biases from the GCMs are generally carried over to the RCMs, which can then reduce or worsen the biases. The bias of the coarse nest is carried over to the fine nest but does not change in amplitude, i.e. the fine nest does not add additional mean bias to the simulations. The spatial pattern of the wet bias over central Europe is similar for all CLM simulations, and leads to a stronger bias in the fine nest simulations compared to that of WRF and REMO. The wet bias in the CLM model is found to be due to a too frequent drizzle, but for higher intensities the distributions are well simulated with both CLM and WRF at the 50 and 7 km resolutions. Also the spatial distributions are close to high resolution gridded observations. The REMO model has low biases in the domain averages over Germany and no drizzle problem, but has a shift in the mean precipitation patterns and a strong overestimation of higher intensities. The GCMs perform well in simulating the intensity distribution of precipitation at their own resolution, but the RCMs add value to the distributions when compared to observations at the fine nest resolution.     

Alpine snow cover in a changing climate: a regional climate model perspective

An analysis is presented of an ensemble of regional climate model (RCM) experiments from the ENSEMBLES project in terms of mean winter snow water equivalent (SWE), the seasonal evolution of snow cover, and the duration of the continuous snow cover season in the European Alps. Two sets of simulations are considered, one driven by GCMs assuming the SRES A1B greenhouse gas scenario for the period 1951–2099, and the other by the ERA-40 reanalysis for the recent past. The simulated SWE for Switzerland for the winters 1971–2000 is validated against an observational data set derived from daily snow depth measurements. Model validation shows that the RCMs are capable of simulating the general spatial and seasonal variability of Alpine snow cover, but generally underestimate snow at elevations below 1,000 m and overestimate snow above 1,500 m. Model biases in snow cover can partly be related to biases in the atmospheric forcing. The analysis of climate projections for the twenty first century reveals high inter-model agreement on the following points: The strongest relative reduction in winter mean SWE is found below 1,500 m, amounting to 40–80 % by mid century relative to 1971–2000 and depending upon the model considered. At these elevations, mean winter temperatures are close to the melting point. At higher elevations the decrease of mean winter SWE is less pronounced but still a robust feature. For instance, at elevations of 2,000–2,500 m, SWE reductions amount to 10–60 % by mid century and to 30–80 % by the end of the century. The duration of the continuous snow cover season shows an asymmetric reduction with strongest shortening in springtime when ablation is the dominant factor for changes in SWE. We also find a substantial ensemble-mean reduction of snow reliability relevant to winter tourism at elevations below about 1,800 m by mid century, and at elevations below about 2,000 m by the end of the century.     

The importance of semi-arid natural mountain pastures for feed intake and recycling of nutrients by traditionally managed goats on the Arabian Peninsula

Goat husbandry in Oman’s Hajar Mountains supplies income and manure to farmers. An earlier analysis concluded that it uses purchased feeds inefficiently, but did not value the contribution of mountain pastures to goat nutrition and cropland fertilization. Therefore intake of pasture vegetation, cultivated forages and purchased feeds was determined in goats from three villages in spring and autumn 2005. Faecal excretion was quantified using TiO₂ and diet digestibility was calculated from faecal nitrogen (N).Organic matter (OM) intake varied from 71 to 107 g kg^−0.75 d⁻¹. Pasture vegetation supplied 45-71% of OM intake, and at least 28%, 33% and 42% of phosphorus (P), metabolizable energy (ME) and N intake. While ME intake just covered maintenance and locomotion requirements, N and P intake exceeded the animals’ requirements. Therefore faecal concentrations (g kg⁻¹ OM) of 26-36 g N and 4-8 g P were high, making goat dung a key element of sustainability for the local cropping systems.Since mountain pastures supply nutrients to goats and cropland, their long-term productivity is crucial. Feeding cultivated forages seemingly reduces intake on pasture, but a comprehensive evaluation of nutritional and economic implications of this strategy and possible alternatives is needed.     

Lead pollution history from 256 BC to AD 2005 inferred from the Pb isotope ratio (<Superscript>206</Superscript>Pb/<Superscript>207</Superscript>Pb) in a varve record of Lake Korttajärvi in Finland

The lead pollution history, based on the accumulation rate of total Pb and ratio of stable isotopes (²⁰⁶Pb/²⁰⁷Pb), was studied in the annually laminated sediment of a small lake in Finland (62°20′ N; 25°41′ E). The sediment chronology based on varve counting provided a unique opportunity to explore and date signals of Pb emissions, including the ancient metallurgical activities of the Roman Empire at the beginning of the Current Era. Changes in the ratio of stable isotopes gave a pronounced signal of the atmospheric Pb fallout in AD 32–392, although this was not distinguishable in the accumulation rate of total Pb, as it was observed in previous work. Calculated accumulations of the ancient pollution Pb were low, the highest values being 0.2–0.3 mg m² a⁻¹ in AD 144–392, corresponding 14–21% of the accumulation of total Pb. The accumulation of pollution Pb collapsed in the fifth century and remained at or close to the background level up to the eleventh century. After this, the accumulation rate of pollution Pb began to increase and reached 1.2 mg m² a⁻¹ in AD 1420–1439, corresponding to 44% of the total Pb accumulation. During five centuries, from AD 1420–1895, the average accumulation of pollution Pb was 2.6 mg m² a⁻¹, the variation being from 0.8 to 4.8 mg m² a⁻¹. The accumulation of Pb started to increase exponentially in the early twentieth century, and the highest accumulations of pollution Pb (11–22 mg m² a⁻¹, corresponding 50–76% of the annual accumulation of total Pb) were dated to AD 1926–1985. The banning of the use of leaded fuel has led to a pronounced decrease in the accumulation of pollution Pb since the 1980s, and the present accumulation rate represents the level that prevailed 80–120 years ago.     

Inferring asteroid surface properties from radar albedos and circular‐polarization ratios

We model electromagnetic scattering from varying closely packed random aggregates of spheres imitating piles of rocks on the surface of an asteroid. We utilize the Multiple Sphere T‐Matrix Method software to study how different parameters affect the radar albedo and the circular‐polarization ratio, for example, the size distribution and electric permittivities of the spherical particles forming the aggregates, and to see if the computed radar albedos and circular‐polarization ratios can be linked to the observational data of asteroids detected using radar. The results of the simulations show the radar albedo and the circular‐polarization ratio as a function of size parameter for different silicate minerals, including anorthosite, peridotite olivine, and basalt. A direct vacuum‐rock surface interface will be considered as well as an approximation for a case in which the rocks are covered by a layer of powdered material, that is, fine regolith. The promising results show values on the range of observed values and imply that the highest circular‐polarization values (μ_c > 1) are measurable only for targets with surface material of high electric permittivity (ε′ > 4.0). However, the asteroid surface model requires further development before more robust conclusions can be made of the surface chemical and structural composition.     

Der Torf und die Torfschichten als historische Urkunden Feuerlands und Patagoniens

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