ALBERT

Notes: 1 It is generally recognized that the vasodilator hydralazine produces hypotension accompanied by baroreflex-mediated tachycardia. In some experimental conditions, however, the accompanying heart rate change is bradycardia, a paradoxical response which has not been satisfactorily explained. The present study examined the possibility of hydralazine-induced bradycardia being mediated by vagal or sympathetic afferents activated by changes in left ventricular pressure. 2 Systolic blood pressure and heart rate responses to hydralazine were recorded in conscious normotensive intact rats by a tail cuff method and compared with responses in animals subjected to previous sino-aortic deafferentation (SAD) to remove the influence of the arterial baroreflex. Responses were also obtained after blockade of myocardial afferent vagal C-fibres with urethane, of efferent vagal impulses to the heart with methylatropine, of positive inotropic effects of hydralazine with atenolol, and of prostanoid sensitization of myocardial nerve fibres with indomethacin. 3 Hydralazine produced hypotension and tachycardia in intact rats, and hypotension and bradycardia in SAD animals. In intact rats, this pattern was not affected by any of the pretreatments, while in SAD rats, all pretreatments reversed the bradycardia to hydralazine. 4 The present results indicate that suppression of the arterial baroreflex by SAD propitiates the appearance of a bradycardiac response to hydralazine. This reaction probably results from activation of a vagal cardiodepressant reflex originating in the heart, as suggested by its blockade by drugs acting at various sites along the reflex arch.

Notes: Sample preparation for the study of humic acids involves a purification treatment to remove both mineral and organic components extracted along with the humic substances. The effects of HCl–HF purification on the chemical composition and structure of humic acids were studied in samples from eight different composts. Only small increases in the concentrations of C, N and H and a decrease in O were found in purified humic acids when compared with the unpurified materials, no more than 10% of average concentration. Total and phenolic acidity increased in the purified materials, whereas carboxylic and carbonyl acidity showed no statistically significant differences as a result of the purification. Gel permeation chromatography showed that only minor changes occurred in molecular size distribution of the humic acids, and the infrared spectra showed no appreciable differences between the purified humic acids and the untreated materials. We conclude that the HCl–HF treatment successfully reduced the ash contents of the humic acids without modifying their chemical composition and structure significantly.

Notes: In Spain, consumption of organic products has not kept pace with production. Up till now, foreign markets have been a natural destination for excess supply. However, world trade liberalization might cause important commercial problems to Spanish producers that could be partially solved by enlarging the domestic market. The goal of this paper is to assess the opportunity for such enlargement focusing on two main aspects: consumers’ and retailers’ attitudes and willingness to pay for organic products. Concerns about health, natural diets or environmental issues could stimulate consumption, while retailing dynamism and competition to gain new market segments might favour distribution. Both aspects are investigated through two surveys addressed to consumers and retailers in two Spanish towns. The results confirm that only a small proportion of consumers and distributors show attitudes that might favour demand expansion. The most sensitized segments are willing to pay more for organic products, but this premium is still very far from the prevailing gap between conventional and organic food products.

Notes: This study provides new constraints on fast cooling and exhumation rates of high-pressure metamorphic rocks in young active mountain belts. Ion microprobe (SHRIMP) U–Pb analysis of zircon in a pyroxenite layer of the Cerro del Almirez ultramafic rocks (Nevado-Filábride Complex, southern Spain) gave an age of 15.0 ± 0.6 Myr (95% c.l.). Mineral inclusions demonstrate that zircon formed close to the high-pressure peak. Combined with previous fission track data, the 15 Myr age suggests high cooling (˜ 80 °C Myr−1) and exhumation (˜1.2 cm yr−1) rates for the unit. The new results indicate that both the Nevado-Filábride Complex and the overlying Alpujárride Complex, with somewhat higher ages and exhumation rates, underwent similar metamorphic evolutions at different times. This implies that the Alpujárride rocks were exhumed when the Nevado-Filábride was subducting and that the same tectonic scenario propagated from one portion of the Betic Cordilleras to another.

Notes: SUMMARY 1. The response of bacterial production (measured as [3H]TdR incorporation rate) to spectral solar radiation was quantified experimentally in an oligotrophic high-mountain lake over 2 years. Bacterial responses were consistent: ultraviolet-B (UVB) was harmful, whereas ultraviolet-A (UVA) + photosynthetically active radiation (PAR) and PAR enhanced bacterial activity. Full sunlight exerted a net stimulatory effect on bacterial activity in mid-summer but a net inhibitory effect towards the end of the ice-free period.2. Experiments were undertaken to examine whether the bacterial response pattern depended on the presence of algae and/or was modulated by the availability of a limiting inorganic nutrient (phosphorus, P). In the absence of algae, [3H]TdR incorporation rates were significantly lower than when algae were present under all light treatments, and the consistent bacterial response was lost. This suggests that the bacterial response to spectral solar radiation depends on fresh-C released from algae, which determines the net stimulatory outcome of damage and repair in mid-summer.3. In the absence of algae, UVB radiation inhibited bacteria when they were strongly P-deficient (mean values of N : P ratio: 46.1), whereas it exerted no direct effect on bacterial activity when they were not P-limited.4. P-enrichment of lake water markedly altered the response of bacteria to spectral solar radiation at the end of ice-free period, when bacteria were strongly P-deficient. Phosphorus enrichment suppressed the inhibitory effect of full sunlight that was observed in October, both in whole lake water (i.e. including algae) and in the absence of algae. This indicates that the bacterial P-deficiency, measured as the cellular N : P ratio, was partly responsible for the net inhibitory effect of full sunlight, implying a high bacterial vulnerability to UVB.

Notes: 1. Natural wetlands have traditionally been considered as efficient ‘ecological engineers’ for waste water treatment. However, the structure and function of many natural wetlands have been severely altered by the chronic exposure to pollutants, especially nutrients.2. Despite the similarity of symptoms of eutrophied shallow lakes and wetlands, restoration strategies differ distinctly between these rather similar aquatic systems. Many of the tools applied in shallow lake restoration programs, for example biomanipulation, have received little attention in wetland management and restoration.3. Although a strong conceptual basis for food web management exists, biotic interactions as influences on wetland communities have been largely neglected by wetland scientists and managers.4. In this paper we show that biomanipulation may have a strong potential for wetland eutrophication abatement. This potential will be demonstrated by reviewing studies carried out in different wetland types in contrasting climatic regions.5. We propose four different scenarios for when, where and why biomanipulation may be used to rehabilitate freshwater wetlands. These scenarios reflect different settings of hydrological variability, eutrophication sources and gradients of wind exposure and water colour.

Notes: SUMMARY 1. The large microgeographical differentiation revealed by allozyme studies in brown trout (Salmo trutta) populations is one of the most striking features of this species. Additionally, allozymes showed great genetic differences between Atlantic and Mediterranean populations on a macrogeographical scale.2. This study was carried out in order to assess whether the great differences observed between Atlantic and Mediterranean populations persisted where the two are geographically close (the ‘microgeographical scale’). Sixteen populations of brown trout, S. trutta, were screened for genetic variation at 25 allozyme loci. The sampling sites, which occupied a relatively small geographical area, were distributed across Cantabrian (Atlantic) and Mediterranean drainages in Northern Spain.3. The neighbour-joining tree, inferred from Nei's genetic distance, showed that brown trout populations clustered into two different groups. These groups corresponded to the Cantabrian and the Mediterranean groups of populations, although no clear geographical pattern emerged within each of the groups. This geographical pattern is basically caused by significant differences in the frequency distribution of the CK-A1* locus, with a higher frequency of *115 in Cantabrian samples (0.586 ± 0.091) while allele *100 was more frequent in Mediterranean samples (0.931 ± 0.038). In addition, this study revealed alleles exclusive to the Mediterranean and Cantabrian populations, agreeing with previous findings.4. Genetic differentiation between Cantabrian and Mediterranean regions (14.19%) was similar to that estimated in Spain at a larger scale (13%), showing that most of the differences between the regions can be observed even in a small geographical area.

Notes: Reliable models are required to assess the impacts of climate change on forest ecosystems. Precise and independent data are essential to assess this accuracy. The flux measurements collected by the EUROFLUX project over a wide range of forest types and climatic regions in Europe allow a critical testing of the process-based models which were developed in the LTEEF project. The ECOCRAFT project complements this with a wealth of independent plant physiological measurements. Thus, it was aimed in this study to test six process-based forest growth models against the flux measurements of six European forest types, taking advantage of a large database with plant physiological parameters.The reliability of both the flux data and parameter values itself was not under discussion in this study. The data provided by the researchers of the EUROFLUX sites, possibly with local corrections, were used with a minor gap-filling procedure to avoid the loss of many days with observations.The model performance is discussed based on their accuracy, generality and realism. Accuracy was evaluated based on the goodness-of-fit with observed values of daily net ecosystem exchange, gross primary production and ecosystem respiration (gC m−2 d−1), and transpiration (kg H2O m−2 d−1). Moreover, accuracy was also evaluated based on systematic and unsystematic errors. Generality was characterized by the applicability of the models to different European forest ecosystems. Reality was evaluated by comparing the modelled and observed responses of gross primary production, ecosystem respiration to radiation and temperature. The results indicated that: Accuracy. All models showed similar high correlation with the measured carbon flux data, and also low systematic and unsystematic prediction errors at one or more sites of flux measurements. The results were similar in the case of several models when the water fluxes were considered. Most models fulfilled the criteria of sufficient accuracy for the ability to predict the carbon and water exchange between forests and the atmosphere. Generality. Three models of six could be applied for both deciduous and coniferous forests. Furthermore, four models were applied both for boreal and temperate conditions. However, no severe water-limited conditions were encountered, and no year-to-year variability could be tested. Realism. Most models fulfil the criterion of realism that the relationships between the modelled phenomena (carbon and water exchange) and environment are described causally. Again several of the models were able to reproduce the responses of measurable variables such as gross primary production (GPP), ecosystem respiration and transpiration to environmental driving factors such as radiation and temperature. Stomatalconductance appears to be the most critical process causing differences in predicted fluxes of carbon and water between those models that accurately describe the annual totals of GPP, ecosystem respiration and transpiration.As a conclusion, several process-based models are available that produce accurate estimates of carbon and water fluxes at several forest sites of Europe. This considerable accuracy fulfils one requirement of models to be able to predict the impacts of climate change on the carbon balance of European forests. However, the generality of the models should be further evaluated by expanding the range of testing over both time and space. In addition, differences in behaviour between models at the process level indicate requirement of further model testing, with special emphasis on modelling stomatal conductance realistically.

Notes: Cauliflower-shaped nodules are widespread in a single red mudstone bed in the Buntsandstein (Triassic) facies of the Iberian Range. They consist mostly of quartz, dolomite and calcite, but other minerals, such as barite, kaolinite and iron oxyhydroxides, are also present. The nodules are spherical, ovoid or elongate in shape and range from 1 to 8 cm across. The surface of the nodules is irregular, and some show a pedogenic coating of microspar. The sedimentological and petrographic data suggest that the initial anhydrite nodules formed through a progressive increase in the porewater concentration of Ca2+ and SO42– in a vadose environment, occasionally under the influence of pedogenic processes. Partial replacement of the anhydrite by megaquartz occurred under more dilute conditions in the same type of setting, as indicated by the presence of organic filaments on the quartz crystal surfaces. In type A nodules, the dissolution of the innermost anhydrite was complete, and different types of quartz cement filled the porosity. Fracturing and meteoric cementation by calcite and minor amounts of kaolinite were the latest processes affecting these nodules. In type B nodules, the dissolution of the anhydrite was incomplete, inhibiting quartz cementation and enabling later dolomitization of the anhydrite. Dolomitization appears to have been driven by sulphate reduction, as indicated by the presence of bacterial bodies within the dolomite crystals. Dedolomitization and precipitation of barite, kaolinite and calcite spar cements occurred later under the influence of meteoric solutions. The nodules may mark the former locations of the water table and provide evidence for an episode of highly evaporitic conditions throughout wide areas of the basin. Their occurrence reveals not only a complex diagenetic history but is also indicative of palaeogeographic and palaeoclimatic conditions.

Notes: Demographic studies were conducted with Lolium rigidum Gaud. growing in winter barley crops at five sites in central and eastern Spain, over a period of 2 or 3 years. Although threefold differences (34–97%) in annual recruitment were recorded in the various experiments, most of the values were close to the overall average (67%). Seedling emergence took place in a very short period of time after sowing, with 90% emergence generally being reached after a thermal time of 242 d°C (provided soil moisture was adequate at sowing). Seedling survival was very high (78–95%) in most experiments, with no clear relationship between this parameter and any of the environmental variables studied. Survival curves were relatively linear, with plant mortality increasing gradually throughout the life cycle of the plant. There were 34-fold differences (from 7 to 237 seeds per plant) in the fecundities recorded in the various experiments. Variation in fecundity resulted partly from differences in crop and weed densities and total precipitation received during the growth cycle. The annual rate of population growth was estimated based on the above-mentioned parameters. The potential for population growth was high (average λ=6.21), but large differences were obtained for the different sites and years.