A review of paired catchment studies for determining changes in water yield resulting from alterations in vegetation

Paired catchment studies have been widely used as a means of determining the magnitude of water yield changes resulting from changes in vegetation. This review focuses on the use of paired catchment studies for determining the changes in water yield at various time scales resulting from permanent changes in vegetation. The review considers long term annual changes, adjustment time scales, the seasonal pattern of flows and changes in both annual and seasonal flow duration curves. The paired catchment studies reported in the literature have been divided into four broad categories: afforestation experiments, deforestation experiments, regrowth experiments and forest conversion experiments. Comparisons between paired catchment results and a mean annual water balance model are presented and show good agreement between the two methodologies. The results highlight the potential underestimation of water yield changes if regrowth experiments are used to predict the likely impact of permanent alterations to a catchment's vegetation. An analysis of annual water yield changes from afforestation, deforestation and regrowth experiments demonstrates that the time taken to reach a new equilibrium under permanent land use change varies considerably. Deforestation experiments reach a new equilibrium more quickly than afforestation experiments. The review of papers reporting seasonal changes in water yield highlights the proportionally larger impact on low flows. Flow duration curve comparison provides a potential means of gaining a greater understanding of the impact of vegetation on the distribution of daily flows.     

Observational and Numerical Study on the Influence of Large-Scale Flow Direction and Coastline Shape on Sea-Breeze Evolution

In this study radar, surface observations and numericalsimulations are used to examine the inland penetrationand intensity of the sea breeze during various large-scaleflow regimes along the curved coastline of the Carolinas,U.S.A. The results clearly indicate that the flow directionrelative to the curved coastline has a significant effecton the sea-breeze evolution.Overall, during northerly flow regimes alongthe curved North Carolina coast, observationsand numerical simulations show that the sea-breezefront has a tendency to remain close to the south-facingcoast. During these same flow regimes the frontmoves further inland relative to the east-facingcoast. The sea-breeze front during westerly flowcases progressed further inland relative to the southcoast and less so from the east-facing coastline.South-westerly flow allows the sea breeze to moveinland from both coastlines but the coastal shapeinfluence makes the inland penetration less fromthe easterly facing beaches. During periods of lightonshore flow (south-east), the sea breeze movesconsiderable distances inland but is not discernableuntil later in the afternoon. The simulations indicatedthat the sea-breeze intensity is greatest (least) when thelarge-scale flow direction has an offshore (onshore)component. Model results indicate the existence of astrong front well inland in the late afternoon duringlight onshore flow. Also noted was that the simulatedsea-breeze front develops earlier in the afternoon duringoffshore regimes and later in the day as the large-scaleflow becomes more onshore. It is concluded that thecoastline shape and coast-relative flow direction areimportant factors in determining how the sea-breezecirculation evolves spatially.     

Reaching critical mass? Theory, politics, and the culture of debate in children's geographies

A small but growing number of voices have begun to raise questions about the current direction of children's geographies as a subfield and its status within the wider discipline. This article intervenes in these emerging discussions to examine the status of debate itself within children's geographies. I argue that children's geographies over the past decade has operated primarily in a consensus-based mode, with a number of potential tensions and differences between practitioners masked as a result. I develop the example of notions of children's competent social agency, a core theoretical assumption that is rarely interrogated in much depth. In closing, I pose questions regarding several contemporary political issues concerning children's agency about which geographers have had surprisingly little to say. I suggest that explicitly addressing some of these vexing issues would contribute to a richer state of debate within children's geographies.     

Sampling Fauna in Stream Sediments as well as Groundwater Using One Net Sampler

Groundwater bores act as traps. Net samplers are regularly used for sampling this type of trap for fauna. To enable direct comparisons of faunal communities in groundwater bores and stream sediments, stream sediment tubes were built similar to groundwater bores and were sampled with net samplers for fauna. These stream sediment tubes consisted of a tube anchored in the stream sediment, also called interstitial space. To test the efficacy of this trap method in stream sediments, it was compared to another type of trap, Hahn's trap. Faunal communities sampled by a net in the stream sediment tubes did not differ hugely from fauna in Hahn's trap samples. Physical and chemical factors of sampled water in both the stream sediment tubes, the surrounding interstitial sediments and the second type of traps, Hahn's traps, showed that water in both the tubes and Hahn's traps was closely related to interstitial water. The net sampler is inexpensive and easy to handle. It is suggested that sampling stream tubes with nets may be an appropriate method for long‐term monitoring studies.     

The solubility of aragonite in seawater—I. Effect of pH and water chemistry at one atmosphere

The effect of water chemistry on the solubility of aragonite in seawater has been defined experimentally as a series of apparent solubility products measured with respect to pH at one atmosphere.The dominant control of the apparent solubility product of aragonite is the carbonate ion concentration, and this is primarily a function of pH. In the light of this fact, we have reconciled our data with 81 other reported values of aragonite solubility by simply examining the water chemistry of the waters in which they were determined.     

Spatial contestation? – The theological foundations of Carl Schmitt’s spatial thought

Carl Schmitt’s work on the political is extensively used as an intellectual point of departure in contemporary academic debates about political contestation. More precisely, Carl Schmitt’s friend versus enemy-distinction is invoked as an essential figuration of political contestation. At the same time, the past few years have seen the attention paid to the spatial thought of Carl Schmitt increase. However, references to the work of Carl Schmitt fail to take the embeddedness of his theories in a complex theological–political–spatial triangle into account. This article aims at joining these readings of Schmitt with regard to the current debate about contestation and space by analyzing the idiosyncratic connection between Carl Schmitt’s Catholic faith, especially in the figure of the katechon, his theory of the political and his conceptualization(s) of space. The underlying logic of his worldview becomes explicit by reviewing his concepts of (a) the nomos, (b) land and sea, (c) the Großraumordnung, as well as (d) the Partisan, which form the benchmarks of his work between the 1930s and the 1960s. Against this background we analyze the value of Schmitt’s work for the ongoing debate about contestation and space. Our core argument is that his understanding of the spatial–political nexus and his metaphysical worldview stand in contrast to contemporary conceptualizations of spatial–political relationships.     

Sediment waves on the Moroccan continental rise

A nearly continuous zone of sediment waves is present on the lower continental rise off western Morocco which parallels the regional bathymetric trends. The individual sediment waves within the zone migrate upslope with time and, in general, also trend parallel to the regional bathymetric contours. These observations suggest that geostrophic contour currents are responsible for the formation of sediment waves. Physical oceanographic measurements and sea-floor photographs indicate only a very weak bottom circulation in this region. This suggests either that strong bottom currents are not essential for the formation of sediment waves or that relatively stronger bottom currents flowed along the continental margin of Morocco in the recent past. Turbidity flows may also influence the distribution of these sediment waves.     

Climate change in Yellowstone National Park: Is the drought-related risk of wildfires increasing?

The increased frequency of wildfires in the United States has become a common prediction associated with the build-up of greenhouse gases. In this investigation, variations in annual wildfire data in Yellowstone National Park are compared to variations in historical climate conditions for the area. Univariate and multivariate analytical techniques reveal that (a) summer temperatures in the Park are increasing, (b) January-June precipitation levels are decreasing, and (c) variations in burn area within the Park are significantly related to the observed variations in climate. Outputs from four different general circulation model simulations for 2 × CO₂ are included in the analyses; model predictions for increasing aridity in the Yellowstone Park area are generally in agreement with observed trends in the historical climate records.