River systems and their sediment flux, Indo-Gangetic plains, Northern Bihar, India

River systems of part of the Himalayan foreland, northern Bihar plains, India, are described in terms of their channel morphology, hydrology and suspended sediment characteristics. A simple classification of the river systems based mainly on the source area characteristics is proposed: (i) mountain-fed, (ii) foothills-fed, (iii) plains-fed and (iv) mixed-fed rivers. Distinct differences are noted between these classes of river systems. Most rivers show evidence of channel movement, mainly by avulsion, but cut-offs also occur locally. The mountain-fed rivers are characterized by very high discharge and low suspended sediment concentration and the plains-fed rivers have relatively low discharge and high suspended sediment concentration. The foothill-fed rivers have moderate values of discharge and suspended sediment concentration. The mountain-fed rivers have built megafans of large extent, whereas the foothills-fed and plains-fed rivers have formed muddy interfan areas. Semi-quantitative estimates of water and sediment flux suggest that about 99·9% of the mass transfer into the plains is water, with the remaining 0·1% being sediment, and that 10% of the latter (0·01% of the total) is retained in the basin, the remainder being transferred to the Bengal Fan.     

DETERMINATION OF THIRTY-TWO MAJOR AND TRACE ELEMENTS IN THREE NIST SOIL SRMS USING ICP-AES AND WDXRF

The National Institute for Standards and Technology (NIST) has recently released three soil standard reference materials that are uncontaminated (SRM 2709), moderately contaminated (SRM 2711), and highly contaminated (SRM 2710) with metals. The SRMs were analyzed at the U.S. Geological Survey (USGS) for thirty two major, minor and trace elements using a combination of wavelength dispersive X-ray fluorescence spectroscopy (WDXRF) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Good agreement is observed between NIST certified values and USGS results. The wide concentration ranges for most transition metals should make these SRMs useful in assessing the accuracy of methods used in geochemical exploration and environmental studies.     

SHORT COMMUNICATION EFFECT OF STANDARDIZATION ON FRAGMENT-BASED MEASURES OF STRUCTURAL SIMILARITY

Substructural fragment occurrence data are widely used as the basis for measures of inter-molecularstructural similarity.This paper investigates the effect of standardization on the effectiveness of suchmeasures using eight data sets for which both structural and biological activity data are available.Eightdifferent standardization methods are studied and it is shown that there is no significant difference in theeffectivenesses of the various methods;accordingly,any of them can be used for the calculation ofintermolecular structural similarity.     

The Geography of Edible Insects in Sub-Saharan Africa: a study of the Mopane Caterpillar

Entomophagy, the human consumption of insects, has not received significant attention in Western literature, despite the critical role which it plays as a protein supplement in many parts of the world. This paper explores the importance of entomophagy in Africa within the context of food security and indigenous technical knowledge. These issues are further investigated through a case study of the mopane caterpillar in Southern Africa. The findings clearly indicate the contribution which insects make to the diet of rural Africans.     

TEMPERATURE PROXY RECORDS COVERING THE LAST TWO MILLENNIA: A TABULAR AND VISUAL OVERVIEW

Proxy data are our only source of knowledge of temperature variability in the period prior to instrumental temperature measurements. Until recently, very few quantitative palaeotemperature records extended back a millennium or more, but the number is now increasing. Here, the first systematic survey is presented, with graphic representations, of most quantitative temperature proxy data records covering the last two millennia that have been published in the peer-reviewed literature. In total, 71 series are presented together with basic essential information on each record. This overview will hopefully assist future palaeoclimatic research by facilitating an orientation among available palaeotemperature records and thus reduce the risk of missing less well-known proxy series. The records show an amplitude between maximum and minimum temperatures during the past two millennia on centennial timescales ranging from c. 0.5 to 4°C and averaging c. 1.5–2°C for both high and low latitudes, although these variations are not always occurring synchronous. Both the Medieval Warm Period, the Little Ice Age and the 20th century warming are clearly visible in most records, whereas the Roman Warm Period and the Dark Age Cold Period are less clearly discernible.     

STORURDI: A LATE HOLOCENE ROCK-SLOPE FAILURE (STURZSTROM) IN THE JOTUNHEIMEN, SOUTHERN NORWAY

An extensive accumulation of rock debris at the mouth of Urdadalen in the Jotunheimen, southern Norway, is interpreted as the deposit of a rock-slope failure (sturzstrom). This is the first large-scale rock-slope failure to be recognised in the Jotunheimen but is unlikely to be the only one. The debris descended to the valley floor, passed across the valley axis and moved 40 m up the opposite side of the valley. Some debris passed over the lip of Urdadalen and now forms a boulder tongue that extends for c. 800 m into Utledalen. A maximum velocity of 80 m s⁻¹ for debris movement from crest of hillside to toe of boulder tongue has been estimated, and a minimum velocity of 28 m s⁻¹ was required for the debris to run up the opposite side of Urdadalen. The degree of boulder hardness/weathering as determined by Schmidt hammer suggests the sturzstrom occurred in the Late Holocene (1.825 ± 0.76 cal. ka bp ), during a period of climatic deterioration. The localised geomorphological impact of the failure event has been to dam the valley and create a small lake, to cause valley widening, to produce a north-facing hillside embayment at 1200–1400 m above sea level with the potential to collect and retain snow that might, in future, lead to niche glacier development and cirque initiation, and to provide a large volume of rock debris for entrainment and onward transport in future glacial cycles.     

NORTH ATLANTIC OSCILLATION SIGNATURES IN WESTERN IBERIAN TREE-RINGS

Exactly dated ring-width chronologies derived from Pyrenean oak and sweet chestnut trees growing in northern Extremadura, Spain, were evaluated for their potential as proxies for regional precipitation and North Atlantic Oscillation variability. The relationships among tree-rings, instrumental climatic records, and three versions of the NAO index were computed for different time subperiods over the last century. The results indicate that tree-ring records reflect, with variable intensity, both short-term and long-term variations in climate. Multiple correlation and regression analysis revealed that summer precipitation appeared to be the major factor affecting tree growth at inter-annual timescales. Moreover, since fluctuations in accumulated variability in annual rainfall over southwest Iberia are controlled by winter precipitation, the accumulated rainfall (August of the year n -1 to July of year n ) and winter NAO indices are also strongly correlated with tree-ring records at interdecadal timescales. This relationship appears to be especially strong during the second half of the 20th century, which is consistent with an increase of the NAO signal in the annual precipitation during the later part of the century. These results indicate that tree-rings from western Iberia are potential proxies of the NAO variability, useful to be included in palaeoclimatic model studies.     

GLACIATION OF MT ALLEN, STEWART ISLAND (RAKIURA): THE SOUTHERN MARGIN OF LGM GLACIATION IN NEW ZEALAND

The origin of two ridges on the eastern slopes of Mt Allen, southern Stewart Island, has remained equivocal, with differences of opinion over the exact process-mechanisms of formation. A variety of approaches was used to test a number of possible hypotheses about the origin of the ridges. These include topographic and spatial positioning, geomorphology, sedimentology and palaeoclimatological extrapolations to reconstruct two small former cirque glaciers with equilibrium line altitudes (ELAs) of c. 600 m. It would appear the two ridges reflect a glacial origin, the glaciers interpreted as forming during the Last Glacial Maximum (LGM) in New Zealand. Whilst glaciation during this time (18–19 ka) was extensive in the Southern Alps, the restricted nature of glaciation on Mt Allen suggests the low altitude restricted glaciation to niche sites on the lee side of upland areas.     

STUDIES ON THE GROWTH OF RHIZOCARPON GEOGRAPHICUM IN NW SCOTLAND, AND SOME IMPLICATIONS FOR LICHENOMETRY

Scotland, a maritime subpolar environment (55–60°N), has seen relatively few applications of lichenometry – even though it offers much potential. Perhaps surprisingly, direct measurements of Rhizocarpon geographicum growth rates in Scotland are so far lacking. This study reports on the growth of this crustose areolate species from two sites in Assynt, NW Scotland, between 2002 and 2009. Repeat photography of 23 non-competing thalli growing under identical environmental conditions on a single vertical surface over 5 years at Inchnadamph showed growth rates to be a function of size – with larger thalli (10–30 mm) growing significantly faster than the smallest thalli (<10 mm). Mean diametral growth rates in thalli >10 mm are 0.67 mm yr⁻¹ (s.d. = 0.16). Studies on a second vertical surface near Lochinver, over 7 years, yielded complex growth data on a more mature population of R. geographicum thalli (<50 mm in diameter). Here, mean diametral growth rates in the larger thalli (>10 mm) are slower (0.29 mm yr⁻¹; s.d. = 0.12) than those at Inchnadamph. However, at this site, competition with other species rules out any meaningful comparison of growth rates between the two sites. Other growth processes were monitored over the five to seven-year study period, including hypothallus growth, areolae development, thallus coalescence, and inter-species competition – all have important implications for the use of Rhizocarpon species in lichenometry.     

SENSITIVITY OF AQUATIC ECOSYSTEMS TO CLIMATIC AND ANTHROPOGENIC CHANGES: THE BASIN AND RANGE,AMERICAN SOUTHWEST AND MEXICO

Variability and unpredictability are characteristics of the aquatic ecosystems, hydrological patterns and climate of the largely dryland region that encompasses the Basin and Range, American Southwest and western Mexico. Neither hydrological nor climatological models for the region are sufficiently developed to describe the magnitude or direction of change in response to increased carbon dioxide; thus, an attempt to predict specific responses of aquatic ecosystems is premature. Instead, we focus on the sensitivity of rivers, streams, springs, wetlands, reservoirs, and lakes of the region to potential changes in climate, especially those inducing a change in hydrological patterns such as amount, timing and predictability of stream flow. The major sensitivities of aquatic ecosystems are their permanence and even existence in the face of potential reduced net basin supply of water, stability of geomorphological structure and riparian ecotones with alterations in disturbance regimes, and water quality changes resulting from a modified water balance. In all of these respects, aquatic ecosystems of the region are also sensitive to the extensive modifications imposed by human use of water resources, which underscores the difficulty of separating this type of anthropogenic change from climate change. We advocate a focus in future research on reconstruction and analysis of past climates and associated ecosystem characteristics, long-term studies to discriminate directional change vs. year to year variability (including evidence of aquatic ecosystem responses or sensitivity to extremes), and studies of ecosystems affected by human activity. © 1997 John Wiley & Sons, Ltd.