Root water compensation sustains transpiration rates in an Australian woodland

© 2014 Elsevier Ltd. We apply a model of root-water uptake to a woodland in Australia to examine the regulation of transpiration by root water compensation (i.e., the ability of roots to regulate root water uptake from different parts of the soil profile depending on local moisture availability). We model soil water movement using the Richards equation and water flow in the xylem with Darcy's equation. These two equations are coupled by a term that governs the exchange of water between soil and root xylem as a function of the difference in water potential between the two. The model is able to reproduce measured diurnal patterns of sap flux and results in leaf water potentials that are consistent with field observations. The model shows that root water compensation is a key process to allow for sustained rates of transpiration across several months. Scenarios with different root depths showed the importance of having a root system deeper than about 2. m to achieve the measured transpiration rates without reducing the leaf water potential to levels inconsistent with field measurements. The model suggests that the presence of more than 5% of the root system below 0.6. m allows trees to maintain sustained transpiration rates keeping leaf water potential levels within the range observed in the field. According to the model, a large contribution to transpiration in dry periods was provided by the roots below 0.3. m, even though the percentage of roots at these depths was less than 40% in all scenarios

Controls on the diurnal streamflow cycles in two subbasins of an alpine headwater catchment

In high-altitude alpine catchments, diurnal streamflow cycles are typically dominated by snowmelt or ice melt. Evapotranspiration-induced diurnal streamflow cycles are less observed in these catchments but might happen simultaneously. During a field campaign in the summer 2012 in an alpine catchment in the Swiss Alps (Val Ferret catchment, 20.4 km2, glaciarized area: 2%), we observed a transition in the early season from a snowmelt to an evapotranspiration-induced diurnal streamflow cycle in one of two monitored subbasins. The two different cycles were of comparable amplitudes and the transition happened within a time span of several days. In the second monitored subbasin, we observed an ice melt-dominated diurnal cycle during the entire season due to the presence of a small glacier. Comparisons between ice melt and evapotranspiration cycles showed that the two processes were happening at the same times of day but with a different sign and a different shape. The amplitude of the ice melt cycle decreased exponentially during the season and was larger than the amplitude of the evapotranspiration cycle which was relatively constant during the season. Our study suggests that an evapotranspiration-dominated diurnal streamflow cycle could damp the ice melt-dominated diurnal streamflow cycle. The two types of diurnal streamflow cycles were separated using a method based on the identification of the active riparian area and measurement of evapotranspiration

Examining the Culture of Poverty Argument in Morocco: How Development, Criminalization, Education, and the Makhzen Craft Perceptions

This paper explores if and how stakeholders in Moroccan poverty reduction invoke the culture of poverty argument. The thesis originally proposed by Oscar Lewis has been used and transformed to justify a variety of policies or lack thereof over the past several decades and varies according to history and cultural context. We understand the notion of what it means to be poor in Morocco through the lens of NGOs working with vulnerable populations. The organizations interviewed in this research were all connected to government or foreign aid funding, which inserts a particular development and Western oriented lens to solutions. Although these organizations may not hold negative views of poor people, shanty towns, and migrants, their solutions are geared towards needs in line with a bureaucratic imposition of knowledge rather than the amplification of existing voices and solutions that these communities already have

Beef Around the World –: Die Globalisierung des Rindfleischhandels bis 1914

Beef around the World. The Globalization of Beef Markets before 1914 Between 1870 and 1914, beef became part of an international trade network between Argentina, Great Britain and the United States. The driving forces behind market integration were the transport revolution, a growing demand for high quality food and a reorganization of trade policies in the transatlantic world. The transport revolution led to a substantial decrease in freight rates and linked distant markets. After the invention of mechanical refrigeration (ca. 1880) not only grain but also ‘dead meat’ could now be shipped at competitive prices. Based on a growing population and increasing incomes the British and North-American consumers developed a higher demand for this high value food. Mass-production and economies of scale in the United States and Argentina created new forms of vertically integrated production, enforced further economic expansion and compelled a novel system of finance and distribution

Agrobusiness und Globalisierung. Die Entstehung des transatlantischen Rindfleischmarktes 1870-1914

Die Arbeit „Agrobusiness und Globalisierung: Die Entstehung des transatlantischen Rindfleischmarktes 1870-1914“ erzählt das erste Kapitel der modernen kapitalistischen Globalisierung. Sie grenzt diese zunächst von der Globalisierung vorindustrieller Prägung ab, beschreibt anschließend ihre Triebkräfte sowohl aus der Perspektive der Angebots- als auch der Nachfrageseite und analysiert schließlich die sie definierenden institutionellen und strukturellen Veränderungen am Beispiel der Entstehung des integrierten, von transnational operierenden Konzernen dominierten transatlantischen Rindfleischmarktes. Ein zusätzliches Kapitel beschäftigt sich mit der politischen Herausbildung der protektionistischen Reaktion des Deutschen Reiches auf diese strukturellen Herausforderungen

How Universal is the Relationship Between Remotely Sensed Vegetation Indices and Crop Leaf Area Index? A Global Assessment

Leaf Area Index (LAI) is a key variable that bridges remote sensing observations to the quantification of agroecosystem processes. In this study, we assessed the universality of the relationships between crop LAI and remotely sensed Vegetation Indices (VIs). We first compiled a global dataset of 1459 in situ quality-controlled crop LAI measurements and collected Landsat satellite images to derive five different VIs including Simple Ratio (SR), Normalized Difference Vegetation Index (NDVI), two versions of the Enhanced Vegetation Index (EVI and EVI2), and Green Chlorophyll Index (CI(sub Green)). Based on this dataset, we developed global LAI-VI relationships for each crop type and VI using symbolic regression and Theil-Sen (TS) robust estimator. Results suggest that the global LAI-VI relationships are statistically significant, crop-specific, and mostly non-linear. These relationships explain more than half of the total variance in ground LAI observations (R2 greater than 0.5), and provide LAI estimates with RMSE below 1.2 m2/m2. Among the five VIs, EVI/EVI2 are the most effective, and the crop-specific LAI-EVI and LAI-EVI2 relationships constructed by TS, are robust when tested by three independent validation datasets of varied spatial scales. While the heterogeneity of agricultural landscapes leads to a diverse set of local LAI-VI relationships, the relationships provided here represent global universality on an average basis, allowing the generation of large-scale spatial-explicit LAI maps. This study contributes to the operationalization of large-area crop modeling and, by extension, has relevance to both fundamental and applied agroecosystem research

Estimation of groundwater consumption by phreatophytes using diurnal water table fluctuations: A saturated-unsaturated flow assessment

This is the published version. Copyright American Geophysical Union[1] Groundwater consumption by phreatophytes is a difficult-to-measure but important component of the water budget in many arid and semiarid environments. Over the past 70 years the consumptive use of groundwater by phreatophytes has been estimated using a method that analyzes diurnal trends in hydrographs from wells that are screened across the water table (White, 1932). The reliability of estimates obtained with this approach has never been rigorously evaluated using saturated-unsaturated flow simulation. We present such an evaluation for common flow geometries and a range of hydraulic properties. Results indicate that the major source of error in the White method is the uncertainty in the estimate of specific yield. Evapotranspirative consumption of groundwater will often be significantly overpredicted with the White method if the effects of drainage time and the depth to the water table on specific yield are ignored. We utilize the concept of readily available specific yield as the basis for estimation of the specific yield value appropriate for use with the White method. Guidelines are defined for estimating readily available specific yield based on sediment texture. Use of these guidelines with the White method should enable the evapotranspirative consumption of groundwater to be more accurately quantified

Associations between autonomic nervous system activity and risk-taking and internalizing behavior in young adolescents

Dysregulated autonomic nervous system (ANS) activity has been associated with adolescent risk-taking and internalizing behavior, but previous results in community samples have been mixed. We investigated whether ANS activity was associated with higher risk-taking and internalizing behavior in young adolescents (age 11/12; n = 875), and whether adolescents' gender, parents' parenting style or a combination of both moderated these associations. Adolescents and their parents were recruited as part of the population-based, longitudinal Amsterdam Born Children and their Development (ABCD) study. Risk-taking behavior was assessed with the Balloon Analogue Risk Task and the personality characteristics sensation seeking and impulsivity, measured with the Substance Use Risk Profile Scale (SURPS). Internalizing behavior was assessed via the SURPS subscales anxiety sensitivity and hopelessness. Authoritative (AUTH-SW) and authoritarian (AUTH-S) parenting styles were measured with the Parenting Styles and Dimensions Questionnaire. Resting ANS activity was assessed via heart rate and respiratory sinus arrhythmia (RSA). Hierarchical, multivariable regression analyses showed higher RSA, but not heart rate, being associated with higher risk-taking behavior and sensation seeking. The associations between ANS activity and risk-taking variables were not significantly moderated by gender, parenting, or interactions between gender and parenting. Our findings suggest that RSA activity may be a relevant factor in mild to moderate risk-taking behavior in adolescents from the general population, regardless of their gender or the type of parenting they experience