Planform Island change assessment for inhabited Lakshadweep Islands

Natural Hazards - Impacts of coastal processes and anthropogenic activities threaten the archipelago of low-lying reef islands. In this study, long-term (1972–2015) and short-term...     

Canopy structure metrics governing stemflow funnelling differ between leafed and leafless states: Insights from a large-scale rainfall simulator

An increasing number of studies have examined the effects of various biotic and abiotic factors on stemflow production. Of those that have ascribed the importance of canopy structure to stemflow production, there has been a bias towards field studies. Coupling Bayesian inference with the NIED (National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan) large-scale rainfall simulator, this study leveraged a unique opportunity to control rainfall amounts and intensities to pinpoint the canopy structural metrics that differentially influence stemflow funnelling ratios for three common tree species between leafed and leafless canopy states. For the first time, we examined whether canopy structure metrics exert a static control on stemflow funnelling ratios or whether different elements of canopy structure are more or less important under leafed or leafless states, thereby allowing us to determine if tacit assumptions about the static influence of canopy structure on stemflow production (and funnelling) are valid (or not). Rainfall simulations were conducted at 15, 20, 30, 40, 50, and 100 mm h⁻¹ under both leafed and leafless tree conditions (12 simulations in total) to detect any differential effects on the presence or absence of foliage on stemflow funnelling ratios. For leafed conditions, the highest percentages of best-fitting models (ΔDIC ≤2) indicated that stemflow funnelling ratios were mainly controlled by total dry aboveground biomass (B_all), diameter at breast height (D_BH), total dry foliar biomass (B_f), tree height (H), and woody to foliar dry biomass ratio (BR). Whilst for the leafless state, the highest percentages of best-fitting models (ΔDIC ≤2) indicated that total dry branch biomass (B_br) was relatively dominant as was the interaction effects between crown projection area and species (CPA:species). These results compel us to reject any assumption of a static effect of different elements of canopy structure on stemflow funnelling.     

GGR Biennial Critical Review: Analytical Developments Since 2010

Advances in the chemical and isotopic characterisation of geological and environmental materials can often be ascribed to technological improvements in analytical hardware. Equally, the creation of novel methods of data acquisition and interpretation, including access to better reference materials, can also be crucial components enabling important breakthroughs. This biennial review highlights key advances in either instrumentation or data acquisition and treatment, which have appeared since January 2010. This review is based on the assessments by scientists prominent in each of the given analytical fields; it is not intended as an exhaustive summary, but rather provides insight from experts of the most significant advances and trends in their given field of expertise. In contrast to earlier reviews, this presentation has been formulated into a unified work, providing a single source covering a broad spectrum of geoanalytical techniques. Additionally, some themes that were not previously emphasised, in particular thermal ionisation mass spectrometry, accelerator‐based methods and vibrational spectroscopy, are also presented in detail.     

Metamorphic reaction rate controlled by fluid pressure not confining pressure: implications of dehydration experiments with gypsum

Pressure is a key control on the progress of metamorphic reactions. When fluids are present in rocks, the fluid pressure is commonly different to the load supported by the solid framework. Here, we show experimentally that, when the two pressures are varied independently, fluid pressure exerts the dominant control on reaction rate, even when the rock is compacting. We present 35 experiments on gypsum dehydration with independently controlled confining pressure, pore fluid pressure and temperature. Results show that a pore fluid pressure decrease at constant confining pressure has a strong effect on the average rate of the reaction. A decrease in confining pressure at constant pore fluid pressure has relatively little effect. Our results have implications for reaction kinetics: even though the product phase is supporting more and more load as reaction proceeds, that load does not appear to exert a chemical effect. On the large scale, our results imply that changes in fluid pressure will drive or stop the progress of metamorphic reactions. When estimating depth at which a metamorphic devolatilization reaction occurs, knowledge of the pore fluid pressure may be necessary rather than commonly used lithostatic pressure. This is relevant for basin diagenesis, mineralization in hydrothermal systems and chemical evolution after pore fluid pressure is perturbed by earthquakes.     

Stumbling upon history: collective memory and the urban landscape

Notable historical events are most commonly commemorated by state-sanctioned monumental structures designed as collective memorials. In contrast, this essay attends to Gunter Demnig’s Stumbling Stones, a countermemorial to the Holocaust, set in the vernacular landscape of cities throughout Europe. As participants in a trip sponsored by the German government, bringing American Jews to the capital city of Berlin, we reflect upon our experiences as we question the narrative differences between monumental memorials and countermemorials. This ethnographic study moves the reader through the crowded boulevards of Germany’s capital city, past historical sites and into museums where we share space and commune with the voices of the past that have come to define individual and collective memory in Berlin.     

Environmental fate of fungicides and other current-use pesticides in a central California estuary

The current study documents the fate of current-use pesticides in an agriculturally-dominated central California coastal estuary by focusing on the occurrence in water, sediment and tissue of resident aquatic organisms. Three fungicides (azoxystrobin, boscalid, and pyraclostrobin), one herbicide (propyzamide) and two organophosphate insecticides (chlorpyrifos and diazinon) were detected frequently. Dissolved pesticide concentrations in the estuary corresponded to the timing of application while bed sediment pesticide concentrations correlated with the distance from potential sources. Fungicides and insecticides were detected frequently in fish and invertebrates collected near the mouth of the estuary and the contaminant profiles differed from the sediment and water collected. This is the first study to document the occurrence of many current-use pesticides, including fungicides, in tissue. Limited information is available on the uptake, accumulation and effects of current-use pesticides on non-target organisms. Additional data are needed to understand the impacts of pesticides, especially in small agriculturally-dominated estuaries.     

Cichlid species diversity in naturally and anthropogenically turbid habitats of Lake Victoria, East Africa

During the past decades, major anthropogenic environmental changes occurred in Lake Victoria, including increased predation pressure due to Nile perch introduction, and decreases in water transparency and dissolved oxygen concentrations due to eutrophication. This resulted in a collapse of the haplochromine cichlids in the sub-littoral waters of the Mwanza Gulf in 1986–1990, followed by a recovery of some species in the 1990s and 2000s, when Nile perch densities declined. We studied two data sets: (1) haplochromines from sand and mud bottoms in the pre-collapse period; (2) haplochromines from sub-littoral areas during the pre-collapse, collapse and recovery periods. Water over mud is murkier and poorer in oxygen than water over sand, and differences in haplochromine communities in these natural habitats during the pre-collapse period may predict the effects of anthropogenic eutrophication during the collapse and recovery periods. In the pre-collapse period, haplochromine densities over sand and mud did not differ, but species richness over sand was 1.6 times higher than over mud bottoms. Orange- and white-blotched colour morphs were most common at the shallowest sand station. More specifically, insectivores and mollusc-shellers had higher numbers of species over sand than over mud, whereas for mollusc-crushers no difference was found. Laboratory experiments revealed that mollusc shelling was more affected by decreased light intensities than mollusc crushing. During the pre-collapse period, spawning occurred year-round in shallow areas with hard substrates and relatively clear water. In deeper areas with mud bottoms, spawning mainly occurred during months in which water clarity was high. No effects of hypoxia on spawning periods were found. It follows that clearer water seems to support differentiation in feeding techniques as well as year-round spawning, and both may facilitate species coexistence. Water clarity is also known to be important for mate choice. These observations may explain why, since the decline of Nile perch, haplochromine densities have recovered, the numbers of hybrids increased and species diversity in the current eutrophic sub-littoral waters has remained 70 % lower than before the environmental changes.     

A Comparison of Design-Based and Model-Based Analysis of Sample Surveys in Geography

Sample surveys are routinely used to gather primary data in human geography research. We highlight the difference between design-based analysis and model-based analysis of sample surveys and emphasize the advantages of using the design-based approach with these data. As an example, we demonstrate differences in results from model-based and design-based analyses of cancer prevalence in a population of predominantly minority women in North Carolina and South Carolina. The results from the two approaches reveal differences in population estimates of numerous variables and a different conclusion regarding the significance of an explanatory variable in a logistic regression model to explain colon cancer prevalence.     

EVALUATION OF BOTANICAL METHODS OF DATING DEBRIS FLOWS AND DEBRIS-FLOW HAZARD IN THE CANADIAN ROCKY MOUNTAINS

The vegetation on debris flow deposits is examined at seven sites in the Canadian Rocky Mountains. Plant cover, colonizing tree ages, species' presence and abundance, and new stem ages on buried willows are vegetation parameters evaluated for the purpose of dating debris flows. The results indicate that general trends of vegetation development on debris flow deposits can be used to date recent events, at least relatively. The use of several methods to corroborate estimations of deposit age is usually necessary. An optimal approach is to combine absolute and relative dating techniques in evaluating debris flow occurrence, extent, and potential hazard.     

RIVER FLOW EVENTS AND VEGETATION COLONIZATION OF POINT BARS IN IOWA

Vegetation on point bars must be adapted to changing hydrological and geomorphological conditions. Detailed population data are gathered for 106 1 m² quadrats on two point bars on the Cedar River, Iowa, in the year following a major establishment event when a brief steady river stage coincided with the dispersal period for common riparian pioneer species (Salix interior, S. nigra, Populus deltoides) during a drought year. Significant differences were found in the location of seedlings and different forms of sprouts on a gradient of elevation. Most seedlings, mostly Salix interior, established in a very narrow range that produced a band along the edge of the river. While density in this band is in part related to sediment texture, it is clear that the densities found (e.g., > 500 m^-2) must result from dispersal by water to the strand line. [Key words: establishment, point bar, riparian, Salix, seedling.]