Estimating source regions for snowmelt runoff in a Rocky Mountain basin: tests of a data‐based conceptual modeling approach

In many mountain basins, river discharge measurements are located far away from runoff source areas. This study tests whether a basic snowmelt runoff conceptual model can be used to estimate relative contributions of different elevation zones to basin‐scale discharge in the Cache la Poudre, a snowmelt‐dominated Rocky Mountain river. Model tests evaluate scenarios that vary model configuration, input variables, and parameter values to determine how these factors affect discharge simulation and the distribution of runoff generation with elevation. Results show that the model simulates basin discharge well (NSCE and R >0.90) when input precipitation and temperature are distributed with different lapse rates, with a rain‐snow threshold parameter between 0 and 3.3 °C, and with a melt rate parameter between 2 and 4 mm °C^?1 d^?1 because these variables and parameters can have compensating interactions with each other and with the runoff coefficient parameter. Only the hydrograph recession parameter can be uniquely defined with this model structure. These non‐unique model scenarios with different configurations, input variables, and parameter values all indicate that the majority of basin discharge comes from elevations above 2900 m, or less than 25% of the basin total area, with a steep increase in runoff generation above 2600 m. However, the simulations produce unrealistically low runoff ratios for elevations above 3000 m, highlighting the need for additional measurements of snow and discharge at under‐sampled elevations to evaluate the accuracy of simulated snow and runoff patterns. Copyright © 2013 John Wiley & Sons, Ltd.     

Wetlandscape hydrologic dynamics driven by shallow groundwater and landscape topography

Wetlands play an important role in watershed eco-hydrology. The occurrence and distribution of wetlands in a landscape are affected by the surface topography and the hydro-climatic conditions. Here, we propose a minimalist probabilistic approach to describe the dynamic behaviour of wetlandscape attributes, including number of inundated wetlands and the statistical properties of wetland stage, surface area, perimeter, and storage volume. The method relies on two major assumptions: (a) wetland bottom hydrologic resistance is negligible; and (b) groundwater level is parallel to the mean terrain elevation. The approach links the number of inundated wetlands (depressions with water) to the distribution of wetland bottoms and divides, and the position of the shallow water table. We compared the wetlandscape attribute dynamics estimated from the probabilistic approach to those determined from a parsimonious hydrologic model for groundwater-dominated wetlands. We test the reliability of the assumptions of both models using data from six cypress dome wetlands in the Green Swamp Wildlife Management Area, Florida. The results of the hydrologic model for groundwater-dominated wetlands showed that the number of inundated wetlands has a unimodal dependence on the groundwater level, as predicted by the probabilistic approach. The proposed models provide a quantitative basis to understand the physical processes that drive the spatiotemporal hydrologic dynamics in wetlandscapes impacted by shallow groundwater fluctuations. Emergent patterns in wetlandscape hydrologic dynamics are of key importance not only for the conservation of water resources, but also for a wide range of eco-hydrological services provided by connectivity between wetlands and their surrounding uplands.     

How robust are global conservation priorities to climate change?

International conservation organisations have identified priority areas for biodiversity conservation. These global-scale prioritisations affect the distribution of funds for conservation interventions. As each organisation has a different focus, each prioritisation scheme is determined by different decision criteria and the resultant priority areas vary considerably. However, little is known about how the priority areas will respond to the impacts of climate change. In this paper, we examined the robustness of eight global-scale prioritisations to climate change under various climate predictions from seven global circulation models. We developed a novel metric of the climate stability for 803 ecoregions based on a recently introduced method to estimate the overlap of climate envelopes. The relationships between the decision criteria and the robustness of the global prioritisation schemes were statistically examined. We found that decision criteria related to level of endemism and landscape fragmentation were strongly correlated with areas predicted to be robust to a changing climate. Hence, policies that prioritise intact areas due to the likely cost efficiency, and assumptions related to the potential to mitigate the impacts of climate change, require further examination. Our findings will help determine where additional management is required to enable biodiversity to adapt to the impacts of climate change.     

The last 750 ka in loess–palaeosol sequences from northern France: environmental background and dating of the western European Palaeolithic

This study presents an overview of Middle Pleistocene loess–palaeosol sequences (LPS) in northern France and discusses the palaeoclimatic significance of the pedosedimentary record in the context of western European LPS and of global climatic cycles for the last 750 ka. In this area, the oldest loess deposits (early Middle Pleistocene) are preserved in sedimentary traps (leeward scarps of fluvial terraces and dissolution sinkholes). They result from local deflation processes reworking Pleistocene sandy fluvial deposits or relicts of Tertiary sands. A large extension of typical calcareous loess over the landscape, the Loess Revolution, is then observed during MIS 6, with heavy mineral assemblages testifying to long-distance transport from the polar desert area of the dried eastern Channel. A correlation scheme is proposed between the global records of northern France in continental environments and both global palaeoclimatic records and other main western European LPS. After 30 years of research, northern France LPS stand as a fundamental archive of the impact of interglacial–glacial climatic cycles as well as millennial events. Finally, these works provide a robust chronoclimatic framework for the study of the western European Late Acheulean and Middle Palaeolithic and for the relative dating of the various fluvial terraces that they fossilise.     

The Holocene tufa at Daours (Somme Valley,northern France): Malacological succession and palaeohydrological implications

One of the thickest and most extensive tufa deposits in northern France occurs at Daours, about 8 km upstream of Amiens at the confluence of the River Somme and its tributary the Hallue. It covers an area of about 80 ha and reaches 10 m above the level of the present valley, probably owing to the construction of a tufa barrage, which caused periodic damming of the valley. The molluscan succession from a 4‐m section through the Daours tufa provides an unusually detailed record of environmental change during the Holocene. The faunal record, supported by four radiocarbon dates, indicates that the tufa sequence at this location does not extend back to the early Holocene but began c. 7340 cal. a BP and ceased to form shortly after c. 4938 cal. a BP, consistent with the notion of a NW European ‘late Holocene tufa decline’. The molluscan record is divisible into six zones that define three aquatic phases separated by three terrestrial episodes, when the tufa surface dried out sufficiently to allow colonization by dry‐ground species, including some shade‐demanding elements. These events are also reflected by differences in the lithology of the tufa. The earliest aquatic phase at the base of the sequence represents the most stable and permanent water‐body. The two subsequent aquatic phases appear to represent smaller, more ephemeral, water‐bodies surrounded by marsh. The land snail assemblages show ecological changes within each terrestrial episode, as well as faunal differences between them. These events, which reflect changes in the local hydrology, were short‐lived, each lasting for only a few hundred years. The tufa at Daours has also yielded flint artefacts and pottery, but it seems unlikely that the dynamic environmental record of the site results from anthropogenic activity.     

Sinusoidal oscillations radiating from a cylindrical source in thermal conduction or groundwater flow: Closed‐form solutions

The diffusion equation governs thermal conduction and groundwater flow phenomena. In this paper, we study the two‐dimensional radial propagation of a sinusoidal perturbation radiating from a cylindrical source within an infinite slab of homogeneous material. The solution of this problem has several applications. For instance, it can be used to determine the hydraulic diffusivity of the subsurface based on measurements of the hydraulic head around a vertical well during its development. For thermal problems, it can be used to determine the thermal diffusivity based on measurements of the temperature distribution around a cylindrical heat source generating a sinusoidal power per unit length. In this paper, we present a comprehensive analytical solution of this problem and we compare these solutions with numerical solutions. Two approximate analytical solutions, which can be relevant in practice, are also presented. Finally, we give an upper bound for the survival time of the transient part of the solution and we provide an estimate of the radius of influence of the sinusoidal solicitation. Copyright © 2010 John Wiley & Sons, Ltd.     

The loess sequence of Dolní Věstonice,Czech Republic: A new OSL‐based chronology of the Last Climatic Cycle

The Dolní Věstonice loess section in the Czech Republic is well known for its high‐resolution loess–palaeosol sequence of the last interglacial–glacial climatic cycle (Upper Pleistocene). The loess section is situated in a climatic transition zone between oceanic and continental climates and is therefore of great value in reconstructing past regional climate conditions and their interaction with climate systems, in particular that of the North Atlantic. Based on a combination of optically stimulated luminescence (OSL) ages, stratigraphic field observations and magnetic susceptibility measurements, a chrono‐climatic interpretation of the Dolní Věstonice loess section is presented. To establish a reliable Upper Pleistocene chronology, a quartz OSL approach was applied for equivalent dose (D_e) determination. Monomineralic quartz extracts of three distinct grain sizes, fine (4–11 μm), middle (38–63 μm) and coarse (90–200 μm), were used and compared. Within error limits, the calculated OSL ages are the same for the different grain sizes, and the OSL ages are in stratigraphic order. The established OSL chronology is in agreement with a Weichselian litho‐ and pedostratigraphy. The Dolní Věstonice loess section is characterized by four pedosedimentary subsequences. At the base of the profile, subsequence I is characterized by a distinct Early Glacial soil complex, OSL‐dated to c. 110 to 70 ka, representing one of the most complete records of environmental change in the European loess belt. Subsequence II is allocated to the Lower Pleniglacial and is characterized by laminated sandy loess. Middle Pleniglacial subsequence III is represented by a brown soil complex, and is followed by the uppermost subsequence IV, characterized by a thick body of laminated sandy loess, indicating strong wind activity and a high sedimentation rate of more than ～1 mm a^?1 during the Upper Pleniglacial. According to the OSL chronology, as well as to the sedimentological and palaeopedological investigations, it is likely that the sequence at Dolní Věstonice has recorded most of the climatic events expressed in the NGRIP δ¹⁸O reference record between 110 and 70 ka.     

First evidence of scavenging behaviour in the herbivorous lizard Uromastyx aegyptia microlepis

In this study, we provide the first evidence of scavenging behaviour in the spiny-tailed agamid lizard (Uromastyx aegyptia microlepis), a species which heretofore has been considered a strict desert herbivore. We examined 294 faecal samples collected in the desert of Qatar and found that 84% of the faeces (n = 247) contained exclusively plant material. Grains of barley (Hordeum vulgare) were present, suggesting that Uromastyx can benefit from the food provided to livestock when wild plants are scarce. We also found remains of invertebrates, vertebrates and stones in the lizard faeces. The type of vertebrate remains found suggests scavenging behaviour and some flexibility in feeding behaviour where food resources are scarce. Overgrazing by camels and goats in the area may affect food availability for Uromastyx populations, suggesting the need for conservation measurements in the Qatar desert.