Phase relations between a circadian rhythm and its zeitgeber within the range of entrainment

The regular day-night changes in tissues, physiologic functions, and behavior of organisms are based on endogenous rhythmic processes which under constant conditions continue with periods slightly deviating from 24h. These ‘arcadian’ rhythms have properties of self-sustained oscillators. Under natural conditions, circadian rhythms are synchronized (entrained) to 24 h by periodic factors in the environment, the so-called ‘Zeitgebers’. In the laboratory, circadian rhythms can also be entrained to periods other than 24 h within certain limits. Data on the phase relationship between the circadian rhythm and an entraining light-dark cycle for vertebrates, insects, plants, and unicellular organisms are reviewed.     

The impact of global change on economic values of water for Public Irrigation Schemes at the São Francisco River Basin in Brazil

Economic values of water for the main Public Irrigation Schemes in the sub-middle region of the São Francisco River Basin, in northeastern Brazil, are determined in this study using an integration of a global agro-economic land and water use (MAgPIE) with a local economic model (Positive Mathematical Programming). As in the latter, the water values depend on the crops grown, and as Brazilian agriculture is strongly influenced by the global market, we used a regionalized version of the global model adapted to the region in order to simulate the crop land use, which is in turn determined by changes in global demand, trade barriers, and climate. The allocation of sugarcane and fruit crops projected with climate change by the global model, showed an impact on the average yields and on the water costs in the main schemes resulting in changes in the water values locally. The economic values for all schemes in the baseline year were higher than the water prices established for agricultural use in the basin. In the future, these water values will be higher in all the schemes. The highest water values currently and in the future were identified in municipalities with a significant proportion of area growing irrigated sugarcane. Being aware of current water values of each user in a baseline year and in a projected future under global climate and socioeconomic changes, decision makers should improve water allocation policies at local scale, in order to avoid conflicts and unsustainable development in the future.     

Farm management decision and response to climate variability and change in Côte d’Ivoire

This paper investigates threats to farm management in the northern and central region of Côte d’Ivoire, with a particular focus on climate-related threats. To this end, farmers’ perception and adaptation strategies for climate change have been analyzed. The data were collected from 205 respondents by means of the Focus Groups method, and they were evaluated using a framework analysis. The main reported threats related to the implementation of farming activities are the high cost of inputs and the lack of technical support, which are followed by diseases, insects, and climate variations (scarcity of rains, strong winds, and high temperature). We find that most farmers have a strong perception of changes in climatic conditions. Their perceived impacts on the local environment through evidences like the disappearance of certain farming practices, occurrence of new insects, and the disruption of key time reference periods. Farmers mainly attempt to adapt by adjusting their agricultural calendar, adopting new short-season varieties, and using mixed cropping. We find that the most influential factors for farmers’ adaptation behavior is lack of contact with extension services and the scarcity of rainfall. Our suggestions for future agricultural policies for better adaptation to climate change are to take into account farmers’ perception, to provide suitable climate forecast, and to improve local technical support.     

Model-based prediction of long-term leaching of contaminants from secondary materials in road constructions and noise protection dams

In this study, contaminant leaching from three different secondary materials (demolition waste, municipal solid waste incineration ash, and blast furnace slag) to groundwater is assessed by numerical modeling. Reactive transport simulations for a noise protection dam and a road dam (a typical German autobahn), in which secondary materials are reused as base layers, were performed to predict the breakthrough of a conservative tracer (i.e., a salt) and sorbing contaminants (e.g., PAHs like naphthalene and phenanthrene or heavy metals) at the groundwater table. The dam constructions have a composite architecture with soil covers in inclined layers and distinct contrasts in the unsaturated hydraulic properties of the used materials. Capillary barrier effects result in strong spatial variabilities of flow and transport velocities. Contaminant breakthrough curves at the groundwater table show significant tailing due to slow sorption kinetics and a wide distribution of travel times. While conservative tracer breakthrough depends primarily on subsoil hydraulic properties, equilibrium distribution coefficients and sorption kinetics represent additional controlling factors for contaminant spreading. Hence, the three secondary materials show pronounced differences in the temporal development of leached contaminant concentrations with consequences for breakthrough times and peak concentrations at the groundwater table. Significant concentration reductions due to dispersion occur only if the source concentrations decrease significantly prior to the arrival of the contaminant at the groundwater table. Biodegradation causes significant reduction of breakthrough concentrations only if flow velocities are low.     

Effect of microbial siderophore DFO-B on Cd accumulation by Thlaspi caerulescens hyperaccumulator in the presence of zeolite

Hyperaccumulators are grown in contaminated soil and water in order that contaminants are taken up and accumulated. Transport of metals from soil to plant is initially dependent on the solubility and mobility of metals in soil solution which is controlled by soil and metal properties and plant physiology. Complexation with organic and inorganic ligands may increase mobility and availability of metals for plants. In this work the influence of desferrioxamine-B (DFO-B), which naturally is produced in the rhizosphere, and zeolite on Cd accumulation in root and shoot of Thlaspi caerulescens (Cd hyperaccumulator) was investigated. Plants were grown in pots with clean quartz sand, amended with 1% zeolite; treatment solutions included 0, 10, and 100 μM Cd and 70 μM DFO-B. Addition of zeolite to the quartz sand significantly reduced Cd concentration in plant tissues and translocation from root to shoot. On contrary, DFO-B considerably enhanced Cd sorption by roots and translocation to aerial part of plants. Treating the plants with zeolite and DFO-B together at 10 μM Cd resulted in reduction of the bioaccumulation factor but enhancement of Cd translocation from root to shoot at the rate of 13%. In contrast, at 100 μM Cd in the solution both bioaccumulation and translocation factors decreased. Total metal accumulation as a key factor for evaluating the efficiency of phytoremediation was highly influenced by treatments. Presence of zeolite in pots significantly decreased total Cd accumulation by plants, whereas, DFO-B clearly enhanced it.     

Anticipating Climate Threshold Damages

Several integrated assessment studies have concluded that future learning about the uncertainties involved in climate change has a considerable effect on welfare but only a small effect on optimal short-term emissions. In other words, learning is important but anticipation of learning is not. We confirm this result in the integrated assessment model “model of investment and technological development” for learning about climate sensitivity and climate damages. If learning about an irreversible threshold is included, though, we show that anticipation can become crucial both in terms of necessary adjustments of pre-learning emissions and resulting welfare gains. We specify conditions on the time of learning and the threshold characteristic, for which this is the case. They can be summarized as a narrow “anticipation window.”