Showing papers by "University of East Anglia published in 1985"

Glacial geology and glaciology of the last mid-latitude ice sheets

Abstract: Satellite imagery and data from ground surveys are used to reconstruct the integrated pattern of the principal longitudinal and transverse features produced on a continent-wide scale by the last ice sheets in Europe and North America. From modern analogues, it is argued that most longitudinal features reflect flow in the outer zone of the ice sheet, and that most major transverse features reflect relatively stable ice-sheet margins. These principles are tested and, using them alone, detailed patterns for the decay of the last ice sheets in North America, Europe and the British Isles are produced, and periods during which they attained near steady-states identified. These patterns can be calibrated by dated sequences to yield deglaciation isochrons. Application of glaciological models to these geological reconstructions generates detailed prediction of net ablation for the period of ice-sheet decay and, by using evidence of last glaciation stratigraphy, models of the dynamic behaviour of the ice sheets throughout the last glacial period are constructed. These enable volumetric changes, oceanic isotopic changes and erratic dispersal pathways to be reconstructed. Erratic dispersal patterns give a good indication of the long-term distribution of centres of ice sheet mass. Discrepancies between predicted and empirical oceanic isotopic records indicate ways in which the conventional continental timescale of glacial change must be altered to fit the better-dated deep ocean record. In addition discrepancies between predicted and empirical erratic dispersal patterns suggest that conventional views of ice-sheet behaviour based on high latitude models may be inappropriate to the dynamically more active mid-latitude ice sheets based in large part on deformable sediment beds.

A systemic pathway in the infection of oilseed rape plants by Leptosphaeria maculans

Abstract: In growth room regimes arranged to simulate field conditions which coincide with natural infection of oilseed rape by Leptosphaeria maculans, leaf inoculation resulted in systemic infection. After colonizing intercellular spaces in the spongy mesophyll of the lamina, the fungus reached a vascular strand and spread down the petiole mainly in xylem vessels or between cells of the xylem parenchyma and cortex, eventually invading and killing cells of the stem cortex and causing the stem canker symptom. The intercellular systemic phase of growth, which was biotrophic and virtually sytnptomless, occurred under a wide range of temperatures.

Democracy at Work

Abstract: Tom Schuller takes as a starting point his belief that there should be a more equitable distribution of power between management and work-force. He reviews the variety of conceptual approaches to industrial democracy and proposes a simple framework for analysis. He concludes that democracy at work necessarily involves the articulation of collective interests, and suggests dimensions in terms of which these interests can most usefully be defined.

Influences of precipitation changes and direct CO2 effects on streamflow

Abstract: Increasing atmospheric carbon dioxide concentrations are expected1 to cause major changes in the world's climate over the next 50–100 yr. The impact of such changes on water resources, through changing precipitation and evaporation, will, however, be complicated by the direct effects of increasing CO2 on vegetation. In controlled environment experiments, higher CO2 levels cause the stomata of plants to close down, decreasing their rate of transpiration and increasing their water use efficiency2. Reduced evapotranspiration would make more water available as runoff and could tend to offset the effects of any CO2-induced reductions in precipitation or enhance the effects of precipitation increases. We consider here, in a simple but revealing analysis, the relative sensitivity of runoff to these two processes, changes in precipitation and changes in evapotranspiration. We show that, for low runoff ratios, small changes in precipitation may cause large changes in runoff. The magnitude and direction of these changes is, however, strongly dependent on the magnitude of the direct CO2 effect on plant evapotranspiration.

Information Systems Definition: The Multiview Approach

Abstract: Multiview - an introduction: A framework for information systems definition. Multiview Stage 1: Analysis of human activity systems The human activity system - perceiving the problem situation The human activity system - defining for further evolution The human activity system - building a conceptual model. Multiview Stage 2: Information modelling: Functions and events Analysis of entities for the information model. Multiview Stage 3: The analysis and design of socio-technical systems The people using the system. Multiview Stage 4: The design of the human-computer interface Human computer interaction Strategies for design. Multiview Stage 5: Designing technical subsystems Design of the technical subsystem Acceptance, maintenance and development. Multiview: Conclusion - Theory and practice.

Analytical solution for the effect of increasing CO2 on global mean temperature

Abstract: Increasing atmospheric carbon dioxide concentration is expected to cause substantial changes in climate1. Recent model studies suggest that the equilibrium warming for a CO2 doubling (Δ T2×) is about 3–4°C2–4. Observational data show that the globe has warmed by about 0.5°C over the past 100 years5,6. Are these two results compatible? To answer this question due account must be taken of oceanic thermal inertia effects, which can significantly slow the response of the climate system to external forcing. The main controlling parameters are the effective diffusivity of the ocean below the upper mixed layer (κ) and the climate sensitivity (defined by Δ T2×). Previous analyses of this problem have considered only limited ranges of these parameters. Here we present a more general analysis of two cases, forcing by a step function change in CO2 concentration and by a steady CO2 increase. The former case may be characterized by a response time which we show is strongly dependent on both κ and Δ T2×. In the latter case the damped response means that, at any given time, the climate system may be quite far removed from its equilibrium with the prevailing CO2 level. In earlier work this equilibrium has been expressed as a lag time, but we show this to be misleading because of the sensitivity of the lag to the history of past CO2 variations. Since both the lag and the degree of disequilibrium are strongly dependent on κ and Δ T2×, and because of uncertainties in the pre-industrial CO2 level, the observed global warming over the past 100 years can be shown to be compatible with a wide range of CO2-doubling temperature changes.

The statistical debate on the net barter terms of trade between primary commodities and manufactures: a comment and some additional evidence*

Abstract: (I950) [P-S] hypothesis. According to this hypothesis, the net barter terms of trade (NBTT) between primary products and manufactures have, over the longrun, exhibited a downward trend.' Spraos presented a detailed and thorough analysis of both the adequacy of the various statistical series available to proxy the NBTT's behaviour over the long-run and the wide range of conceptual (including quality) problems involved in such an exercise. On the basis of his analysis, Spraos concluded that the balance of the evidence for the seventy-year period ending with the outbreak of World War II supported the P-S hypothesis of a secular deterioration in the NBTT. It should, however, be noted that the evidence also suggested that the particular series cho-sen for analysis by Prebisch (I950) himself did appear to exaggerate, possibly to a large extent, the rate of deterioration. However, when the analysis was extended to include the post World War II period, Spraos found that 'while the deteriorating tendency cannot be decisively refuted, it is open to doubt... when the record up to the I970S is taken into account' (i980, p. I26). As we shall see in this paper, closer scrutiny reveals a statistical problem with Spraos's analysis and the purpose of this paper is to show that, once appropriate action is taken to overcome this problem, some quite strong evidence in support of the P-S hypothesis emerges. The paper is organised as follows: Section I briefly discusses Spraos's methodology and Section II discusses an econometric issue arising from this analysis. Section III presents our empirical evidence, while Section IV summarises the main findings of the paper.

Measurements of various sulphur gases in a coastal marine environment

Abstract: Measurements of several sulphur gases have been made in coastal seawaters (including microlayers) and marine air off Great Yarmouth, U.K., and in a freshwater lake. The results show dimethyl sulphide to be the dominant sulphur gas in all the waters examined, with lesser amounts of carbonyl sulphide and carbon disulphide. For the marine air and water samples carbonyl sulphide showed no significant seasonal variation in concentration. The seawater was always supersaturated with respect to the carbonyl sulphide concentration in the air; the mean saturation value being 4.6. Likewise the seawater was always supersaturated with dimethyl sulphide, but for this gas the concentrations in the water showed substantial seasonal variation (× 40), with a maximum value of about 500 ng(S) l-1 in late June, approximately contemporaneous with the second plankton bloom in the region. Sea surface microlayers harvested cryogenically showed a mean enrichment of 2.4 relative to subsurface water for carbonyl sulphide. Some part of the observed microlayer enrichment for this gas may be due to freezing-on of atmospheric carbonyl sulphide onto the frozen microlayer sample. In general, microlayer samples did not exhibit a significant enrichment for dimethyl sulphide. However, under conditions of high biological production, enrichments of several-fold were found, but may be attributable, at least in part, to biological production of dimethyl sulphide in the microlayer water in the period between collection and analysis.

An interhemispheric comparison of the concentrations of bromine compounds in the atmosphere

Abstract: At least seven organic bromine compounds have been positively identified in the atmosphere1,2 (CH3Br, CH2Br2, CHBr3, CH2BrCl, CF3Br, CF2BrCl and C2H4Br2) and others have been observed in coastal seawater samples (C2H5Br, C3H7Br and CHBr2Cl) (S. A. P. and R. A. Rasmussen, unpublished data). The atmospheric chemistry of bromine compounds has considerable consequence in the stratosphere, where bromine acts as a more efficient catalyst than chlorine in removing ozone3,4. Several bromine compounds also fulfil an important role in the geochemical cycling of the element through the troposphere5. Here we present measurements of four bromine compounds (CF3Br, CH3Br, CH2Br2 and CHBr3) over a large latitudinal range (40° N to 75° S). These data suggest that the major source of bromine in the atmosphere could be bromoform (CHBr3), probably emitted from the ocean and with a short lifetime due to photolysis. Our data also suggest that the major emission of methyl bromide (CH3Br), and hence most bromine entering the stratosphere, will be anthropogenic.

Liberty, Preference, and Choice

Abstract: Ever since its first publication in 1970, Amartya Sen's paper “The Impossibility of a Paretian Liberal” (reprinted in Sen, 1982) has served as the starting point for almost all discussions of liberty in social choice theory However, a number of people, myself included, have argued that Sen's theorem rests on a misleading characterization of liberty (Nozick, 1974, pp 164–166; Bernholz, 1974; Sugden, 1978, 1981, pp 193–198; Garden-fors, 1981; Levi, 1982) In a recent paper, addressed to a philosophical audience, Sen (1983) has provided a careful defence of his theorem against this charge I shall argue that this defence does not work

Relocation and Preferential Elution of Acidic Solute through the Snowpack of a Small, Remote, High-Altitude Scottish Catchment

Abstract: This isolated snowpack shows wide spatial variability in composition, with 15 samples from a 700 m transect giving coefficients of variance of more than 50% for most of the major ions Cations showed somewhat less variability than anions Preferential elution, ie the more rapid loss of some ions from the pack than others, was more readily observed in the composition of meltwaters because of the high variability in snowpack composition Preferential elution could be found in the snowpack where it was possible to resample a well-defined surface during a period of ablation The elution sequence established from these surfaces was although the position of the hydrogen and ammonium ions may be affected by buffering The sequence compares reasonably well with a generalized one assembled from earlier studies, where is usually eluted quickly and sodium and chloride rather slowly The evolution of the snowpack composition towards solute depletion, but relative richness in chloride, is clearly represented in triangular diagrams

Population biology of salt marsh and sand dune annuals

Abstract: Annuals represent a significant component of the vegetation of coastal salt marshes and sand dunes. From many points of view, the two habitats might appear to have little in common. Yet both are characterized by episodes of low water potential, marked spatial and temporal heterogeneity and a zonation which, within certain limits, reflects successional change.

The predatory Chironomidae of an iron-rich stream: feeding ecology and food web structure

Abstract: . 1. Three species of Tanypodinae (Chironomidae) were found in an acid and iron-rich stream in southern England. Maximum abundance was achieved in summer and they were sparse at other times. Individuals were aggregated on the stream bed and were overrepresented in accumulations of leaf litter. 2. The diets of all three species consisted of a mixture of prey (prominently detritivorous chironomid larvae) and detritus. More detritus and fewer prey were taken in winter than in summer. 3. When comparing large tanypod species with small and, intraspecifically, late instars with early, the proportion of guts containing prey increased with increasing body size. 4. Stonefly larvae were more prominent in the diet of Zavrelimyia barbatipes (Kieffer) in summer than in winter but for the other two species the reverse was true. A bigger proportion of Trissopelopia longimana (Staeger) guts contained prey in early summer than in August whereas more Macropelopia goetghebueri (Kieffer) guts contained prey in August. This was apparently a consequence of seasonal differences in the distribution of body size among the populations of these two species. 5. The stream contains two further common predators, Plectrocnemia conspersa (Curtis) and Sialis fuliginosa Pict. These are important predators of tanypod larvae but might also compete with them since they severely deplete populations of prey taken in common. 6. Analysis of the food-web in Broadstone Stream reveals remarkably high values of connectance (C and Cmax) and of species richness times connectance (SCmax). Such characteristics are theoretically associated with fragile and dynamically unstable food webs, and may be found in ‘constant’ environments. There is also an apparently unusual prevalence of omnivory in the community.

The elution of ions through field and laboratory snowpacks

Abstract: It has been recognised for many years that the first fraction of meltwater from a melting snowpack contains a much higher concentration of ions than that of the bulk (or average) snow of which the pack is comprised (Foster 1978, Johannessen and Henriksen 1978). This process leads to the so called “acid flush” in the spring and can have severe ecological effects on lakes and streams (Hagen and Langeland 1973, Leivestad and Muniz 1976, National Research Council of Canada 1981). We have studied elution of ions through a snowpack on Folgefonna near Bergen, Norway, and in the laboratory. In the field we collected meltwater samples at hourly intervals for a period of 4 d at the start of the melt season, and analyzed them for pH, , Cl−, Na+, Mg2+, Ca2+ and K+. 2 m cores were also collected at the beginning and end of the experiment in order to study bulk changes in snow composition. The meltwaters showed a diurnal cycle with high ionic concentrations around noon, with and levels rising by factors of up to four and six-fold compared to the average concentrations on the first day. Cl− levels peaked much later, after the and levels had decreased, and only reached 2.3 times their lowest concentrations. pH values were strongly correlated with and levels, suggesting that a significant proportion of these anions were in the form of strong acids. The laboratory experiments involved slow melting of snow samples collected in the Cairngorm mountains, Scotland, and also showed that and (and also Mg2+ and K+) ions were removed from the snow preferentially whilst Na+ and Cl− tended to remain longer. The position of H+ within the ion elution sequence is unclear due to uncertainties in the absolute determination of pH in the field measurements, but the laboratory experiments confirm the differential rates of elution shown in the Norwegian snowpack and reaffirms its importance in the acidification of streams during spring.

Plant structure and the foraging success of Aphidius rhopalosiphi (Hymenoptera: Aphidiidae)

Abstract: . 1. A study of searching behaviour on wheat and host preference of Aphidius rhopalosiphi (DeStefani-Perez) is described. 2. Parasitoids divided their time equally between the leaves but spent very little time on the ear. 3. After contact with honeydew or an aphid host, parasitoids were arrested in a particular area and increased the time spent searching. 4. Aphids feeding on the ear were parasitized less successfully, since their position between the grains protected them from parasitoid attacks. 5. A.rhopalosiphi exhibited no preference for Metopolophium dirhodum (Walker) or Sitobion avenae (Fabricius), although the handling time for the latter was significantly longer; this resulted in fewer S.avenae being parasitized when it was abundant. Parasitoids did not switch between hosts in these experiments. 6. As a result of its searching behaviour, A.rhopalosiphi will encounter and parasitize M.dirhodum feeding on the leaves more frequently than S.avenae, which feeds on the ear. This will limit the parasitoid's ability to regulate populations of the cereal aphid S. avenae.

A hybrid zone between Chorthippus parallelus parallelus and Chorthippus parallelus erythropus (Orthoptera: Acrididae): behavioural characters

Abstract: Two subspecies of the grasshopper Chorthippus parallelus have ranges that abut in the Pyrenees. Males produce two types of song—calling song and courtship song. We have examined the use and structure of these songs in males from nine sites near Mont-Louis, Pyrenees-Onentales, France. These sites were previously used to identify the position of the hybrid zone on morphological characters. The subspecies differ in the use and structure of both types of song. Clines in these characters correspond in position with the morphological cline. At least one character may be relevant to mate choice but none of the characters show evidence of reinforcement.

A hybrid zone between Chorthippus parallelus parallelus and Chorthippus parallelus erythropus (Orthoptera: Acrididae): morphological and electrophoretic characters

Abstract: Two subspecies of the grasshopper Chorthippus parullelus have distributions that abut in the Pyrenees. We have studied morphological and electrophoretic variation in II populations near Mont Louis, Pyrenees-Orientales, France. The two subspecies differ in several morphological characters and at one enzyme locus, esterase-2, and in this area they hybridize forming a cline in morphology less than 5 km wide. Examination of museum specimens suggests that this hybrid zone extends for most of the length of the Pyrenees, possibly breaking down in the extreme west. As the two subspecies are known to differ in mating behaviour this hybrid zone is well suited to the study of reinforcement.