ALBERT

Notes: Two sequential extractions with unbuffered 0.1 m BaCl2 were done to study the release of salt-exchangeable H+ and Al from mineral horizons of five Podzols and a Cambisol. Released Al was found to have a charge close to 3+ in all horizons and in both extractions. This finding was supported by the near-equality of the titrated exchangeable acidity (EAT) and the sum of exchangeable acids (EA = He + 3Ale, calculated from the pH and Al concentration of the extract). The ratio between EA of the second and the first extraction was over 0.50 in the Bs2 and C horizons and smaller in the other horizons. H+ was assumed to be in equilibrium with weak acid groups, and the modified Henderson–Hasselbach equation, pKHH = pH − n log (α/(1 − α)), was used to explain pH of the extract. The degree of dissociation (α) was calculated as the ratio between effective and potential cation exchange capacity. Value of the empirical constant n was found to be near unity in most horizons. When the monoprotic acid dissociation was assumed in all horizons, pKHH had the same value in both extractions. For Al3+, two equilibrium models were evaluated, describing (i) complexation reactions of Al3+ with soil organic matter, and (ii) equilibrium with Al(OH)3. Apparent equilibrium constants were written as (i) pKo = xpH − pAl3+, and (ii) log Qgibbs= log Al3+ − 3log H+. The two extractions gave an average reaction stoichiometry x close to 2 in all horizons. Results suggest that an equilibrium with organic Al complexes can be used to express dissolved Al3+, aluminium being apparently bound to bidentate sites. The value of log Qgibbs was below the solubility of gibbsite (log Kgibbs = 8.04) in many horizons. In addition, log Qgibbs of the second extraction was greater than that of the first extraction in all horizons except the C horizon. This indicates that equilibrium with Al(OH)3 cannot explain dissolved Al3+ in the soils. We propose that the models of pKHH and pKo can be used to simulate exchangeable H+ and Al3+ in soil acidification models.

Notes: The Gaines–Thomas selectivity coefficient, K, was used to express the relation between the cations in solution and the cations in exchange sites in podzolic forest soils. Soil solution was obtained by centrifuging a fresh bulked soil sample. Exchangeable cations HX, AlX, CaX, MgX and KX and effective cation-exchange capacity, CECe, were determined with 0.1 m BaCl2. Apparent values of K indicated a preference of Ca2+ over Mg2+ and over Al3+ in O, A and B horizons (log KAl–Ca 〈 0 and log KMg–Ca 〈 0), whereas log KK–Ca and log KH–Ca exceeded zero. The horizons were similar with respect to log KH–Ca, and the differences in log KMg–Ca were small. Log KK–Ca and log KAl–Ca increased in the horizons in the order O 〈 A 〈 B. Log KAl–Ca was not significantly correlated with the fraction AlX/CECe. Log KMg–Ca was positively correlated with the fractions HX/CECe and AlX/CECe, and negatively correlated with log (CaX/MgX). The selectivity coefficient of binary cation exchange seemed to be applicable to in situ soil solutions. However, the fraction of each cation on exchange sites should be based on the CECe rather than on the sum of the two cations. The latter, also, seemed to be acceptable in cases of exchangeable cations with a large relative content in soil, e.g. in Al3+–Ca2+ exchange in A and B horizons, and in H+–Ca2+ exchange in O and A horizons.

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: Abstract The utilisation of antidiabetic drugs reflects both the prevalence of diabetes and the different therapeutic traditions of physicians. A questionnaire survey to study attitudes to the use of oral antidiabetic drugs amongst physicians and possible changes in treatment habits was carried out in a representative sample of Finnish physicians (n=454) in 1992 and the results were compared with those of a similar survey carried out in 1985, and with drug utilisation statistics. The mean fasting blood glucose level at which a physician would start pharmacological treatment was 8.7 mmol·l−1, which was significantly lower than in the 1985 survey. The responses to various case histories suggested a more active approach to pharmacological treatment compared to the 1985 survey. Insulin treatment especially seems to have gained in popularity. This change in attitude was paralled by an increase in the consumption of antidiabetic drugs in Finland during the observation period. The increase in use of oral drugs was steeper in Finland than in Norway and Sweden. Whether this active approach will improve the metabolic control and prognosis of patients with Type 2 diabetes, remains to be demonstrated.

Notes: Summary A double-blind comparison of the β-blockers metoprolol, alprenolol and oxprenolol was carried out to evaluate their antihypertensive effect and tolerability. 105 patients with previously untreated hypertension entered the trial and 71 completed it. Side-effects were infrequent and were never the reason for drop-out. All three drugs caused a statistically significant reduction in blood-pressure at the lower of the two doses used during a dose-finding period. At the higher dose employed in this period, metoprolol caused a significantly greater reduction in diastolic blood-pressure than did alprenolol or oxprenolol. All three drugs caused a significant reduction in heart rate. During the follow-up period, the β-blockers were supplemented if necessary with hydrochlorothiazide. This was required less frequently in the metoprolol group than in the other two groups.

Notes: Summary The antihypertensive effect of a new sustained-release matrix formulation of verapamil 200 mg was investigated in a dose-response study in patients with mild to moderate essential hypertension. Noninvasive ambulatory blood pressure measurements were recorded over 24 h in 6 patients with diastolic blood pressure ≥100 mmHg. The patients received sustained-release verapamil 200 mg once daily and twice daily in a randomized order. Each medication period lasted 2 weeks. Verapamil 200 mg twice daily had a better antihypertensive effect than the same dose once daily. After a 6-week placebo period 27 patients with a diastolic blood pressure ≥100 mmHg were included in a double-blind clinical trial. The patients received sustained release verapamil 200 mg once daily and twice daily in a randomized crossover manner. Each medication period lasted 6 weeks, with an intervening 6-week placebo period. A diastolic blood pressure of ≤95 mmHg was achieved in 6 patients with the once-daily regimen and in 14 with the twice-daily regimen. The mean fall in diastolic blood pressure was 4 and 9 mmHg, respectively (p〈0.05). We conclude that sustained-release verapamil 200 mg once daily gives a satisfactory blood pressure response only in a minority of patients, while 200 mg twice daily has a significantly better antihypertensive effect. Both doses were well tolerated.

Notes: Abstract Solution cation concentrations and base cation leaching were simulated for a homogenous soil block and a soil showing five horizons of a podzolic forest soil. The dynamic model ACIDIC simulated water flow, nutrient uptake for tree growth, and cation exchange between H+, Al3+, Ca2+, Mg2+ and K+ in forest soil. In the multi-layer simulations exchangeable base cation concentrations changed most in the O horizon. The subsoil had a decisive effect on the pH of the runoff and base cation leaching from the soil. The one-layer model underestimated Ca and Mg leaching and overestimated H+ and Al concentrations in the runoff. In the eluvial and the top of illuvial horizon the solution Al / (Ca + Mg) ratio exceeded that in one-layer structure more than 10-fold. Cases with the horizon-specific cation exchange coefficient values and mean coefficient values for all layers showed only minor differences in Al / (Ca + Mg) ratio. The vertical variation in the soil chemical properties should be accounted for even if some details of processes and parameters were unavailable.

Notes: Abstract Apparent cation–exchange equilibria and solubility of aluminium were analysed in two acidic forest soils: a Cambisol and a Cambic Podzol. Soil solution was obtained by a centrifuge drainage method from fresh soil samples and with suction lysimeters. The total positive charge of the measured cations as well as the concentrations of the cations were generally much larger in the centrifugates than in the lysimeter solutions, which implies that total charge of soil solution is larger in small pores than in large pores. Hydrogen ion in particular was concentrated in some of the centrifugates, the ratio centrifugate:lysimeter solution being over 10. The total positive charge of the measured cationsdecreased with increasing depth with both methods. Theapparent cation–exchange coefficients K H-Ca, K Al-Ca, and K K-Ca had different values in the methods, and the variation in the cation exchange coefficients was larger in the lysimeter method than in the centrifuging method. The coefficient K Mg-Ca had similar values in both methods. The results imply that mobile solution could not have cation–exchange equilibria with bulk exchangeable cations in the soils, although solution in small pores seemed to have equilibria. Solubility of Al did not follow the solubility of an Al(OH)3 phase in the centrifugates, and the centrifugates with a H+ activity larger than 60 μmol were undersaturated with respect to the gibbsite. Solubility of Al was between gibbsite and amorphousAl(OH)3 in the lysimeter solutions. Differencesbetween the centrifugates and the lysimeter solutionsin the ion concentrations and in the apparent chemicalequilibria were similar for both soils studied.