Spatial heterogeneity confounded ozone-exposure experiment in semi-natural grassland

Interpretation of observations from manipulative experiments is often complicated by a multitude of uncontrolled processes operating at various spatial and temporal scales. As such processes may differ among experimental plots there is a risk that effects of experimental treatments are confounded. Here we report on a free-air ozone-exposure experiment in permanent semi-natural grassland that suggested strong ozone effects on community productivity after 5years. We tested ozone effects and investigated the potential of confounding due to changes in nutrient management. Repeated-measure ANOVA revealed mainly negative temporal trends for frequency of abundant productive plant species. Constrained ordination additionally showed converging trajectories of species compositions for ozone and control treatments with time. Yields sampled prior to the start of the experiment and soil nitrogen concentrations revealed that spatial heterogeneity in the soil nutrient status was not accounted for by the random allocation of treatments to plots with a bias towards less productive patches in the elevated-ozone plots. Re-analysis of yield data using repeated-measure ANOVA with a covariable to account for productivity prior to the start of fumigation revealed effects on the temporal changes in total yield and yield of legumes that cannot be separated between ozone and pre-treatment nutrient status. Changes in species composition favour an ecological interpretation with spatial heterogeneity as the major cause of different yield declines. Although elevated ozone may cause subtle physiological changes with longer term implications, our new results suggest that species-rich mature grassland such as the one studied at Le Mouret may be less sensitive to elevated ozone than previously assumed. In this experiment a confounded design was hidden at the start by transitory effects of a prior change in nutrient treatment

Video-assisted thoracoscopic pericardial fenestration for loculated or recurrent effusions

Objective: The validity of video-assisted thoracoscopic pericardial fenestration was prospectively assessed for loculated effusions, effusions previously treated by percutaneous catheter manoeuvres and those with concurrent pleural diseases. Methods: Inclusion criteria consisted of echocardiographically documented pericardial effusions requiring diagnosis or relief of symptoms and recurrent effusions after failed percutaneous drainage and balloon pericardiotomy. Pre-operative CT-scan was used to delineate additional pleural pathology and to determine the side of intervention. All patients were followed clinically and by echocardiographic examination 3 months post-operatively. Results: Twenty-four patients underwent thoracoscopic pericardial fenestration with 11 patients (54%) being previously treated by percutaneous catheter drainage, balloon pericardiotomy or subxyphoidal fenestration. Pre-operative echocardiography revealed septation and loculation in 18 patients (72%). Additional pleural pathology was identified on CT scan in 12 patients (50%) and talc pleurodesis was performed in six patients, all suffering from malignant pleural effusion. The mean operation time was 45 min (range 30-60 min) with no complications being observed. All patients were followed 3 months post-operatively by clinical and echocardiographic examination; relief of symptoms was achieved in all patients but echocardiography showed a recurrence in one patient (4%). Another recurrence was found by echocardiography after a mean follow-up time of 33 months in the 12 patients suffering from a non-malignant pericardial effusion. No recurrence of pleural or pericardial effusion was observed in the subset of patients with talc pleurodesis. Conclusion: Video-assisted thoracoscopic pericardial fenestration is safe and effective for loculated pericardial effusions previously treated by percutaneous drainage manoeuvres and those with concomitant pleural diseas

Diastolic dysfunction precedes myocardial hypertrophy in the development of hypertension

Background: Left ventricular (LV) hypertrophy and impaired diastolic function may occur early in systemic hypertension, but longitudinal studies are missing. Methods: We performed an echocardiographic follow-up study in young initially normotensive male offspring of hypertensive (OHyp) (n = 25) and normotensive (ONorm) (n = 17) parents. Blood pressure (BP), LV mass, and mitral inflow were determined at baseline and after 5 years. Pulmonary vein flow pattern assessment and septal myocardial Doppler imaging were additionally performed at follow-up. Results: At follow-up, BP was not significantly different between the two groups (128 ± 11 / 84 ± 10 v 123 ± 11 / 81 ± 5 mm Hg, OHyp v ONorm) but five OHyp had developed mild hypertension. LV mass index remained unchanged and was not different between the two groups at follow-up (92 ± 17 v 92 ± 14 g/m2). Diastolic echocardiographic properties were similar at baseline, but, at follow-up, the following differences were found: mitral E deceleration time (209 ± 32 v 185 ± 36 msec, P < .05) and pulmonary vein reverse A wave duration (121 ± 15 v 107 ± 12 msec, P < .05) were prolonged in the OHyp as compared to the ONorm. Compared to the normotensive subjects, the five OHyp who developed hypertension had more pronounced alterations of LV diastolic function, that is, significantly higher mitral A (54 ± 7 v 44 ± 9 cm/sec, hypertensives v normotensives, P < .05), lower E/A ratio (1.31 ± 0.14 v 1.82 ± 0.48, P < .05), increased systolic-to-diastolic pulmonary vein flow ratio (1.11 ± 0.3 v 0.81 ± 0.16, P < .005), longer myocardial isovolumic relaxation time (57 ± 7 v 46 ± 12 msec, P < .05) as well as smaller myocardial E (10 ± 1 v 13 ± 2 cm/sec, P < .05) and E/A ratio (1.29 ± 0.25 v 1.78 ± 0.43, P < .05), despite similar LV mass (91 ± 16 v 93 ± 18 g/m2). Conclusion: Over a 5-year follow-up, initially lean, normotensive, young men with a moderate genetic risk for hypertension, developed Doppler echocardiographic alterations of LV diastolic function compared to matched offspring of normotensive parents. These alterations were more pronounced in the OHyp who developed mild hypertension and occurred without a distinct rise in LV mass. Am J Hypertens 2001;14:106-113 © 2001 American Journal of Hypertension, Lt

Adaptation options under climate change for multifunctional agriculture: a simulation study for western Switzerland

Besides its primary role in producing food and fiber, agriculture also has relevant effects on several other functions, such as management of renewable natural resources. Climate change (CC) may lead to new trade-offs between agricultural functions or aggravate existing ones, but suitable agricultural management may maintain or even improve the ability of agroecosystems to supply these functions. Hence, it is necessary to identify relevant drivers (e.g., cropping practices, local conditions) and their interactions, and how they affect agricultural functions in a changing climate. The goal of this study was to use a modeling framework to analyze the sensitivity of indicators of three important agricultural functions, namely crop yield (food and fiber production function), soil erosion (soil conservation function), and nutrient leaching (clean water provision function), to a wide range of agricultural practices for current and future climate conditions. In a two-step approach, cropping practices that explain high proportions of variance of the different indicators were first identified by an analysis of variance-based sensitivity analysis. Then, most suitable combinations of practices to achieve best performance with respect to each indicator were extracted, and trade-offs were analyzed. The procedure was applied to a region in western Switzerland, considering two different soil types to test the importance of local environmental constraints. Results show that the sensitivity of crop yield and soil erosion due to management is high, while nutrient leaching mostly depends on soil type. We found that the influence of most agricultural practices does not change significantly with CC; only irrigation becomes more relevant as a consequence of decreasing summer rainfall. Trade-offs were identified when focusing on best performances of each indicator separately, and these were amplified under CC. For adaptation to CC in the selected study region, conservation soil management and the use of cropped grasslands appear to be the most suitable options to avoid trade-offs

Incorporation of atmospheric 15NO2-nitrogen into free amino acids by Norway spruce Picea abies (L.) Karst.

During spring and autumn 1991, potted 6-yearold spruce trees (Picea abies (L.) Karst.) were fumigated with 60 nl1–1 15NO2 for 4 days under controlled conditions in constant light. Current and previous flush needles, the bark and the fine roots were analysed for total 15N content and incorporation of 15N into the -amino nitrogen of free amino acids. In addition, in vitro nitrate reductase activity and stomatal conductance of the needles were measured. Nitrate reductase activity was significantly higher in the needles of fumigated trees compared to control trees exposed to filtered air. With an average of 9.1% 15N, free glutamate was the pool with the most label. Taking into account the time-course of the labelling of this pool, this figure can be taken as an estimate of the minimum contribution of NO2 to the N nutrition of the needles. 15N-labelled amino acids were also detected in the bark and the roots, indicating export from the needles

Adapting agricultural land management to climate change: a regional multi-objective optimization approach

In several regions of the world, climate change is expected to have severe impacts on agricultural systems. Changes in land management are one way to adapt to future climatic conditions, including land-use changes and local adjustments of agricultural practices. In previous studies, options for adaptation have mostly been explored by testing alternative scenarios. Systematic explorations of land management possibilities using optimization approaches were so far mainly restricted to studies of land and resource management under constant climatic conditions. In this study, we bridge this gap and exploit the benefits of multi-objective regional optimization for identifying optimum land management adaptations to climate change. We design a multi-objective optimization routine that integrates a generic crop model and considers two climate scenarios for 2050 in a meso-scale catchment on the Swiss Central Plateau with already limited water resources. The results indicate that adaptation will be necessary in the study area to cope with a decrease in productivity by 0-10%, an increase in soil loss by 25-35%, and an increase in N-leaching by 30-45%. Adaptation options identified here exhibit conflicts between productivity and environmental goals, but compromises are possible. Necessary management changes include (i) adjustments of crop shares, i.e. increasing the proportion of early harvested winter cereals at the expense of irrigated spring crops, (ii) widespread use of reduced tillage, (iii) allocation of irrigated areas to soils with low water-retention capacity at lower elevations, and (iv) conversion of some pre-alpine grasslands to cropland

Station-scale bias correction and uncertainty analysis for the estimation of irrigation water requirements in the Swiss Rhone catchment under climate change

Irrigation water requirements (IWR) are expected to be influenced by changes in the climate variables driving water availability in the soil-plant system. Most of the agricultural surface areas of the heterogeneous Swiss Rhone catchment are already exposed to drought. Aiming at investigating future pressures on the water resources to fill the growing gap between rain-fed and optimum water supply for cultivation, we downscaled and bias corrected 16 regional climate scenarios from the ENSEMBLES dataset for the period 1951-2050 using a Quantile Mapping methodology calibrated with daily observations from 5 contrasting weather stations. The data reveal an increased evaporative demand over the growing season for almost all stations and scenarios (2021-2049 vs. 1981-2009). The picture is less clear for precipitation, with a projected decrease or increase depending on the scenario, station and month. The main results indicate that bias correction of climate scenarios not only reduces the remaining error between baseline and observations but also enhances the change signal in seasonal IWR estimates. This is due to a higher and more realistic sensitivity of IWR to the atmospheric water budget, the slope of this relationship being steeper in the observations than in the uncorrected data. The seasonal cycle of the IWR change signal shows different sensitivities and climate drivers across crops (grassland and maize) and stations, but a consistent trend towards an increase despite uncertainty. This increased water demand will have to be reconciled with possibly decreased or shifted future water availability from glacier and snow melt

Current and future ozone risks to global terrestrial biodiversity and ecosystem processes

Risks associated with exposure of individual plant species to ozone (O3) are well documented, but implications for terrestrial biodiversity and ecosystem processes have received insufficient attention. This is an important gap because feedbacks to the atmosphere may change as future O3 levels increase or decrease, depending on air quality and climate policies. Global simulation of O3 using the Community Earth System Model (CESM) revealed that in 2000, about 40% of the Global 200 terrestrial ecoregions (ER) were exposed to O3 above thresholds for ecological risks, with highest exposures in North America and Southern Europe, where there is field evidence of adverse effects of O3, and in central Asia. Experimental studies show that O3 can adversely affect the growth and flowering of plants and alter species composition and richness, although some communities can be resilient. Additional effects include changes in water flux regulation, pollination efficiency, and plant pathogen development. Recent research is unraveling a range of effects belowground, including changes in soil invertebrates, plant litter quantity and quality, decomposition, and nutrient cycling and carbon pools. Changes are likely slow and may take decades to become detectable. CESM simulations for 2050 show that O3 exposure under emission scenario RCP8.5 increases in all major biomes and that policies represented in scenario RCP4.5 do not lead to a general reduction in O3 risks; rather, 50% of ERs still show an increase in exposure. Although a conceptual model is lacking to extrapolate documented effects to ERs with limited or no local information, and there is uncertainty about interactions with nitrogen input and climate change, the analysis suggests that in many ERs, O3 risks will persist for biodiversity at different trophic levels, and for a range of ecosystem processes and feedbacks, which deserves more attention when assessing ecological implications of future atmospheric pollution and climate change