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 croplands.

Natural tracer profiles across argillaceous formations

Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl(-), Br(-)), water isotopes (delta(18)O, delta(2)H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in Mazurek et al. (2009). Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the entire data set. In essentially all cases, the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles. Transport by advection has a negligible influence on the observed profiles at most sites, as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data. The advantages and disadvantages of different conservative tracers are also assessed. The anion Cl(-) is well suited as a natural tracer in aquitards, because its concentration varies considerably in environmental waters. It can easily be measured, although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue. The stable water isotopes are also well suited, but they are more difficult to measure and their values generally exhibit a smaller relative range of variation. Chlorine isotopes (delta(37)Cl) and He are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence. It is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion, leading to relatively sharp changes of boundary conditions, can be considered as a pre-requisite to obtain well-interpretable tracer signatures. On the other hand, gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation.

[Treatment of ascites, hyponatremia and hepatorenal syndrome in liver cirrhosis]

Ascites and hyponatremia are frequent complications of advanced liver cirrhosis. Over 50 % of cirrhotic patients develop ascites and about one third gets hyponatremic. The development of ascites is due to an increased sodium retention in the kidneys, leading to expansion of extracellular volume and accumulation of fluid in the peritoneum. Hyponatremia is related to an impairment in the renal capacity to eliminate solute-free water that causes water retention that is disproportionate to the sodium retention, thus causing a reduction in serum sodium concentration. The exact pathogenesis of sodium retention is not clear, yet. The main pathogenic factor responsible for hyponatremia is a nonosmotic hypersecretion of vasopressin from the neurohypophysis. There is evidence suggesting that hyponatremia predisposes to hepatic encephalopathy. Impairment in glomerular filtration rate in hepatorenal syndrome is due to renal vasoconstriction. Treatment of ascites consists of potassium sparing diuretics, loop diuretics, and/or paracentesis. The current standard of care of hyponatremia based on fluid restriction is unsatisfactory. Currently, a new family of drugs, known as vaptans, which act by specifically antagonizing the effects of vasopressin on the V2 receptors located in the kidney, is evaluated for their role in the management of hyponatremia. Because data on long-term administration are still incomplete, they cannot be used routinely, yet. Liver transplantation is the treatment of choice for hepatorenal syndrome. As bridge to transplantation long-term administration of intravenous albumin and vasoconstrictors can be used.

The effect of an oral glucose load on sodium and water excretion after rapid intravenous infusion of 0.9% (w/v) saline

Previous studies have suggested that oral or intravenous glucose enhances salt and water retention following a saline load. To test this, we studied the effects of an oral glucose load on urinary sodium and water excretion and serum biochemistry in response to a 2l intravenous infusion of 0.9% saline in normal subjects.

Body salt and water balances in cardiothoracic surgery patients with intensive care unit-acquired hyponatremia

PURPOSE Hyponatremia is frequently observed in intensive care unit (ICU) patients, but there is still lack information on the physiological mechanisms of development. MATERIALS AND METHODS In this retrospective analysis we performed tonicity balances in 54 patients with ICU acquired hyponatremia. We calculated fluid and solute in and outputs during 24 hours in 106 patient days with decreasing serum-sodium levels. RESULTS We could observe a positive fluid balance as a single reason for hyponatremia in 25% of patients and a negative solute balance in 57%. In 18% both factors contributed to the decrease in serum-sodium. Hyponatremic patients had renal water retention, measured by electrolyte free water clearance calculation in 79% and positive input of free water in 67% as reasons for decline of serum-sodium. The theoretical change of serum sodium during 24 hours according to the calculations of measured balances correlated well with the real change of serum sodium (r = 0.78, P < .01). CONCLUSIONS Balance studies showed that renal water retention together with renal sodium loss and high electrolyte free water input are the major contributors to the development of hyponatremia. Control of renal water and sodium handling by urine analysis may contribute to a better fluid management in the ICU population.

Field-scale water transport in unsaturated crystalline rock

Safe disposal of toxic wastes in geologic formations requires minimal water and gas movement in the vicinity of storage areas, Ventilation of repository tunnels or caverns built in solid rock can desaturate the near field up to a distance of meters from the rock surface, even when the surrounding geological formation is saturated and under hydrostatic pressures. A tunnel segment at the Grimsel test site located in the Aare granite of the Bernese Alps (central Switzerland) has been subjected to a resaturation and, subsequently, to a controlled desaturation, Using thermocouple psychrometers (TP) and time domain reflectometry (TDR), the water potentials psi and water contents theta were measured within the unsaturated granodiorite matrix near the tunnel wall at depths between 0 and 160 cm. During the resaturation the water potentials in the first 30 cm from the rock surface changed within weeks from values of less than -1.5 MPa to near saturation. They returned to the negative initial values during desaturation, The dynamics of this saturation-desaturation regime could be monitored very sensitively using the thermocouple psychrometers, The TDR measurements indicated that water contents changed dose to the surface, but at deeper installation depths the observed changes were within the experimental noise. The field-measured data of the desaturation cycle were used to test the predictive capabilities of the hydraulic parameter functions that were derived from the water retention characteristics psi(theta) determined in the laboratory. A depth-invariant saturated hydraulic conductivity k(s) = 3.0 x 10(-11) m s(-1) was estimated from the psi(t) data at all measurement depths, using the one-dimensional, unsaturated water flow and transport model HYDRUS Vogel er al., 1996, For individual measurement depths, the estimated k(s) varied between 9.8 x 10(-12) and 6.1 x 10(-11) The fitted k(s) values fell within the range of previously estimated k(s) for this location and led to a satisfactory description of the data, even though the model did not include transport of water vapor.

Measurements of a water potential and water content in unsaturated crystalline rock

A water desaturation zone develops around a tunnel in water-saturated rock when the evaporative water loss at the rock surface is larger than the water flow from the surrounding saturated region of restricted permeability. We describe the methods with which such water desaturation processes in rock materials can be quantified. The water retention characteristic theta(psi) of crystalline rock samples was determined with a pressure membrane apparatus. The negative water potential, identical to the capillary pressure, psi, below the tensiometric range (psi < -0.1 MPa) can be measured with thermocouple psychrometers (TP), and the volumetric water contents, theta, by means of time domain reflectometry (TDR). These standard methods were adapted for measuring the water status in a macroscopically unfissured granodiorite with a total porosity of approximately 0.01. The measured water retention curve of granodiorite samples from the Grimsel test site (central Switzerland) exhibits a shape which is typical for bimodal pore size distributions. The measured bimodality is probably an artifact of a large surface ratio of solid/voids. The thermocouples were installed without a metallic screen using the cavity drilled into the granodiorite as a measuring chamber. The water potentials observed in a cylindrical granodiorite monolith ranged between -0.1 and -3.0 MPa; those near the wall in a ventilated tunnel between -0.1 and -2.2 MPa. Two types of three-rod TDR Probes were used, one as a depth probe inserted into the rock, the other as a surface probe using three copper stripes attached to the surface for detecting water content changes in the rock-to-air boundary. The TDR signal was smoothed with a low-pass filter, and the signal length determined based on the first derivative of the trace. Despite the low porosity of crystalline rock these standard methods are applicable to describe the unsaturated zone in solid rock and may also be used in other consolidated materials such as concrete.

Molecular characterization of five porcine candidate genes for drip loss in pork

Drip loss is the loss of fluid from a piece of meat without mechanical force and represents an important meat quality trait. Previous work revealed a quantitative trait locus (QTL) for drip loss in pork in an experimental Duroc x Pietrain (DUPI) F2 family on SSC 5. Based on functional data indicating their possible involvement in water holding capacity and their expression in skeletal muscle, we selected five positional candidates (ACO2, ADSL, CBY1, KCNJ4, PLA2AG6) out of 130 predicted genes in the QTL interval for further analysis. We performed a mutation analysis of all coding exons and discovered 204 polymorphisms. We genotyped 39 single nucleotide polymorphisms (SNPs) in 192 Pietrain pigs with extreme drip loss phenotypes and detected a possible association with drip loss for one non-coding SNP in the ADSL gene (ss107793818, p(raw) = 0.021). Correspondingly, ADSL diplotypes were associated with drip loss and pH1 of M. longissimus dorsi. However, after correction for multiple testing, none of the tested SNPs were significantly associated with drip loss. One possible explanation for these results is that one of the QTL-alleles from the experimental DUPI family may be fixed or nearly fixed in the tested Pietrain population.

Nutrition in clinical practice-the refeeding syndrome: illustrative cases and guidelines for prevention and treatment

The refeeding syndrome is a potentially lethal complication of refeeding in patients who are severely malnourished from whatever cause. Too rapid refeeding, particularly with carbohydrate may precipitate a number of metabolic and pathophysiological complications, which may adversely affect the cardiac, respiratory, haematological, hepatic and neuromuscular systems leading to clinical complications and even death. We aimed to review the development of the refeeding syndrome in a variety of situations and, from this and the literature, devise guidelines to prevent and treat the condition. We report seven cases illustrating different aspects of the refeeding syndrome and the measures used to treat it. The specific complications encountered, their physiological mechanisms, identification of patients at risk, and prevention and treatment are discussed. Each case developed one or more of the features of the refeeding syndrome including deficiencies and low plasma levels of potassium, phosphate, magnesium and thiamine combined with salt and water retention. These responded to specific interventions. In most cases, these abnormalities could have been anticipated and prevented. The main features of the refeeding syndrome are described with a protocol to anticipate, prevent and treat the condition in adults.

The role of adrenal steroidogenesis in arterial hypertension

Adrenal aldosterone production, the major regulator of salt and water retention, is discussed with respect to hypertensive diseases. Physiological aldosterone production is tightly regulated, either stimulated or inhibited, in the adrenal zona glomerulosa by both circulating factors and/or by locally derived endothelial factors. Arterial hypertension caused by volume overload is the leading clinical symptom indicating increased mineralocorticoid hormones. Excessive aldosterone production is seen in adenomatous disease of the adrenals. The balance between stimulatory/proliferative and antagonistic signaling is disturbed by expression of altered receptor subtypes in the adenomas. Increased aldosterone production without a detectable adenoma is the most frequent form of primary aldosteronism. Both increased sensitivity to agonistic signals and activating polymorphisms within the aldosterone synthase gene (CYP11B2) have been associated with excessive aldosterone production. 17alpha-Hydroxylase deficiency and glucocorticoidremediable aldosteronism can also cause excessive mineralocorticoid synthesis. In contrast, the severe form of pregnancy-induced hypertension, preeclampsia, is characterized by a compromised volume expansion in the presence of inappropriately low aldosterone levels. Initial evidence suggests that compromised CYP11B2 is causative, and that administration of NaCl lowered blood pressure in pregnant patients with low aldosterone availability due to a loss of function.

[Hyponatraemia in patients with neurosurgical disorders: SIADH or cerebral salt wasting syndrome?]

Patients with neurosurgical disorders often present with hyponatraemia. Two mechanisms account for hyponatraemia in these patients: the Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH) and Cerebral Salt Wasting Syndrome (CSWS). The two entities differ in their volume status. In SIADH, volume is expanded due to ADH-mediated renal water retention, but in CSWS, volume is diminished as a consequence of renal salt wasting, most likely attributable to an increased secretion of Brain Natriuretic Peptide (BNP) and Artrial Natriuretic Peptide (ANP). Since it is clinically difficult to distinguish between these two entities, fluid management has to be performed carefully. Salt and fluid replacement appears to be indicated in CSWS, whereas fluid restriction might be the primary approach in patients with SIADH.

[Cross-talk between heart and kidney--mechanisms and management of the cardiorenal syndrome from a nephrologists view]

Renal dysfunction represents a frequent comorbidity in patients with in chronic heart failure and is not only a strong predictor of mortality, but also causally linked to the development and progression of CHF. Mechanisms involved in the cross-talk between the kidney and the heart include the up-regulated sympathetic nerve system, activation of the renin-angiotensin-aldosterone system, vasopressin release and decreased activity of arterial baroreceptors and natriuretic peptides resulting in abnormal salt and water retention. The main therapeutic goals for patients with the so-called cardiorenal syndrome is the normalization of volume status while avoiding overdiuresis and renal dysfunction as well as the implementation of an evidence-based pharmacologic treatment to improve patient outcome. If these two goals are not achieved with conventional therapy, renal replacement therapy should be discussed in an interdisciplinary approach. All current renal replacement techniques have proved to be useful in controlling hypervolemia and ameliorating functional cardiac parameters and quality of life in patients with heart failure. Nevertheless, the influence of renal replacement therapy on long-term survival of affected patients has not been addressed in large controlled studies.

Combined effect of heterogeneity, anisotropy and saturation on steady state flow and transport: Structure recognition and numerical simulation

1 Natural soil profiles may be interpreted as an arrangement of parts which are characterized by properties like hydraulic conductivity and water retention function. These parts form a complicated structure. Characterizing the soil structure is fundamental in subsurface hydrology because it has a crucial influence on flow and transport and defines the patterns of many ecological processes. We applied an image analysis method for recognition and classification of visual soil attributes in order to model flow and transport through a man-made soil profile. Modeled and measured saturation-dependent effective parameters were compared. We found that characterizing and describing conductivity patterns in soils with sharp conductivity contrasts is feasible. Differently, solving flow and transport on the basis of these conductivity maps is difficult and, in general, requires special care for representation of small-scale processes.

High exchangeable calcium concentrations in soils on Barro Colorado Island, Panama

The soils on four lithologies (basaltic conglomerates, Bohio; Andesite; volcanoclastic sediments with basaltic agglomerates, Caimito volcanic; foraminiferal limestone, Caimito marine) on Barro Colorado Island (BCI) have high exchangeable Ca concentrations and cation-exchange capacities (CEC) compared to other tropical soils on similar parent material. In the 0–10 cm layer of 24 mineral soils, pH values ranged from 5.7 (Caimito volcanic and Andesite) to 6.5 (Caimito marine), concentrations of exchangeable Ca from 134 mmolc kg− 1 (Caimito volcanic) to 585 mmolc kg− 1 (Caimito marine), and cation exchange capacities from 317 mmolc kg− 1 (Caimito volcanic) to 933 mmolc kg− 1 (Caimito marine). X-ray diffractometry of the fraction < 2 μm revealed that smectites dominated the clay mineral assemblage in soil except on Caimito volcanic, where kaolinite was the dominant clay mineral. Exchangeable Ca concentrations decreased with increasing soil depth except on Caimito marine. The weathering indices Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA) and Weathering Index of Parker (WIP) determined for five soils on all geological formations, suggested that in contrast to expectation the topsoil (0–10 cm) appeared to be the least and the subsoil (50–70 cm) and saprolite (isomorphically weathered rock in the soil matrix) the most weathered. Additionally, the weathering indices indicated depletion of base cations and enrichment of Al-(hydr)oxides throughout the soil profile. Tree species did not have an effect on soil properties. Impeded leaching and the related occurrence of overland flow seem to be important in determining clay mineralogy. Our results suggest that (i) edaphic conditions favor the formation of smectites on most lithologies resulting in high CEC and thus high retention capacity for Ca and (ii) that there is an external source such as dust or sea spray deposition supplying Ca to the soils.

DYPTOP: a cost-efficient TOPMODEL implementation to simulate sub-grid spatio-temporal dynamics of global wetlands and peatlands

Simulating the spatio-temporal dynamics of inundation is key to understanding the role of wetlands under past and future climate change. Earlier modelling studies have mostly relied on fixed prescribed peatland maps and inundation time series of limited temporal coverage. Here, we describe and assess the the Dynamical Peatland Model Based on TOPMODEL (DYPTOP), which predicts the extent of inundation based on a computationally efficient TOPMODEL implementation. This approach rests on an empirical, grid-cell-specific relationship between the mean soil water balance and the flooded area. DYPTOP combines the simulated inundation extent and its temporal persistency with criteria for the ecosystem water balance and the modelled peatland-specific soil carbon balance to predict the global distribution of peatlands. We apply DYPTOP in combination with the LPX-Bern DGVM and benchmark the global-scale distribution, extent, and seasonality of inundation against satellite data. DYPTOP successfully predicts the spatial distribution and extent of wetlands and major boreal and tropical peatland complexes and reveals the governing limitations to peatland occurrence across the globe. Peatlands covering large boreal lowlands are reproduced only when accounting for a positive feedback induced by the enhanced mean soil water holding capacity in peatland-dominated regions. DYPTOP is designed to minimize input data requirements, optimizes computational efficiency and allows for a modular adoption in Earth system models.