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Regional Trends (regional + trend)
Selected AbstractsChanges in seasonal and annual high-frequency air temperature variability in the Arctic from 1951 to 1990INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2002Rajmund Przybylak Abstract A detailed analysis of intraseasonal (within season) and interannual (between years) temperature variability for the whole Arctic for the period 1951,90 is provided. For this purpose four temperature variables were used: average (TMEAN), maximum (TMAX) and minimum (TMIN) temperatures, and the diurnal temperature range (DTR). The source data for the analysis were the daily TMAX and TMIN for ten stations representing almost all climatic regions in the Arctic. The methods of calculation of temperature variability were mostly taken from Plummer (1996; Australian Meteorological Magazine45: 233). Thus the results presented for the Arctic can be fully compared with existing results for the other parts of the world (China, the former USSR, the USA and Australia). Regional trends in intraseasonal and interannual temperature variability were mixed and the majority of them were insignificant. Trends in intraseasonal variability were positive in the Norwegian Arctic and eastern Greenland and negative in the Canadian and Russian Arctic. Small increases in interannual variability for all temperature variables were observed annually in the Norwegian Arctic and eastern Greenland, and in the Canadian Arctic. These were largely a result of increases in winter and transitional seasons respectively. On the other hand, opposite tendencies, both on a seasonal and an annual basis, occurred in the Russian Arctic. Statistically significant negative trends in intraseasonal variability were noted mainly in the Canadian Arctic, whereas such trends in interannual variability were noted mainly in the Russian Arctic. The absence of significant changes in intraseasonal and interannual variability of TMEAN, TMAX, TMIN and DTR is additional evidence (besides the average temperature) that in the Arctic in the period 1951,90 no tangible manifestations of the greenhouse effect can be identified. Copyright © 2002 Royal Meteorological Society. [source] Network-magnetotelluric method and its first results in central and eastern Hokkaido, NE JapanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2001Makoto Uyeshima Summary A new field observation technique based on the magnetotelluric (MT) method has been developed to determine deep and large-scale 3-D electrical conductivity distributions in the Earth. The method is named ,Network-MT', and employs a commercial telephone network, to measure voltage differences with long dipole lengths ranging from 10 to several tens of kilometres. This observation configuration enables us to obtain the telluric field distribution with nearly continuous coverage over a target region. Response functions are estimated between the respective voltage differences and the horizontal magnetic fields at a reference point. Owing to the long electrode spacing, the observed responses are relatively free from the effects of small-scale near-surface heterogeneity with a scalelength shorter than the typical electrode spacing. Therefore, physically meaningful direct comparison between the observations and model responses is feasible even if the fine-scale features of near-surface heterogeneity are ignored. This extensively reduces the difficulty, especially in 3-D MT interpretation. The first Network-MT experiment was performed in central and eastern Hokkaido, NE Japan, in 1989. It took about five months to complete all of the measurements, and used 209 dipoles to cover the target area of 200(EW) × 200(NS) km2. The long electrode spacing enabled us to obtain the voltage differences with a high signal-to-noise ratio. For 175 dipoles, the squared multiple coherency between the voltage difference and the horizontal magnetic field at Memambetsu Geomagnetic Observatory was determined to be more than 0.9 in the period from 102 to 104 s. 193 MT impedances were computed in tensor form by linear combination of the response functions. The estimated impedances generally possessed smooth period dependence throughout the period range. No drastic spatial change was observed in the characteristics of the tensors for neighbouring sites, and some regional trend could be detected in the spatial distribution. Thus, we confirmed the merit of the Network-MT method, that its responses are little affected by small-scale near-surface structures. The regional feature of the response implied a significant influence of the coast effect, and was well correlated with the regional geological setting in Hokkaido. Conventional Groom,Bailey tensor decomposition analysis revealed that the target region is not regionally one- or two-dimensional. Therefore, we developed a 3-D forward modelling scheme specially designed for the Network-MT experiment, and tried to reproduce the Network-MT responses directly. In the 3-D model, a realistic land,sea distribution was considered. The resistivity of sea water was fixed to be 0.25 , m and, as a first trial of 3-D modelling, the resistivity of the land was assumed to be uniform and its value was determined to be 200 , m by a simple one-parameter inversion. Overall agreements between the observations and the best-fit model responses indicated the importance of the 3-D coast effect in the target region. However, there remained significant discrepancies, especially in the phase of the responses, which provide a clue to determining a regional deep 3-D structure. [source] Employment Deconcentration: A New Perspective on America's Postwar Urban EvolutionJOURNAL OF REGIONAL SCIENCE, Issue 3 2002Gerald Carlino In this study we show that during the postwar era the United States experienced a decline in the share of urban employment accounted for by the relatively dense metropolitan areas and a corresponding rise in the share of relatively less dense ones. This trend, which we call employment deconcentration, is distinct from the other well,known regional trend, namely, the postwar movement of jobs and people from the frostbelt to the sunbelt. We also show that deconcentration has been accompanied by a similar trend within metropolitan areas, wherein employment share of the more dense sections of MSAs has declined and that of the less dense sections risen. We provide a general equilibrium model with density,driven congestion costs to suggest an explanation for employment deconcentration. [source] Mollusk species diversity in the Southeastern Pacific: why are there more species towards the pole?ECOGRAPHY, Issue 2 2003Claudio Valdovinos The most ubiquitous and well recognized diversity pattern at large spatial scales is the latitudinal increase in species richness near the equator and decline towards the poles. Although several exceptions to this pattern have been documented, shallow water mollusks, the most specious group of marine invertebrates, are the epitome of the monotonic decline in species diversity toward higher latitudes along the Pacific and Atlantic coasts of North America. Here we analyze the geographic diversity of 629 mollusk species along the Pacific South American shelf. Our analyses are based on the most complete database of invertebrates assembled for this region of the world, consisting of latitudinal ranges of over 95% of all described mollusks between 10° and 55°S. Along this coast, mollusk diversity did not follow the typical latitudinal trend. The number of species remained constant and relatively low at intermediate latitudes and sharply increased toward higher latitudes, south of 42°S. This trend was explained by changes in shelf area, but not by sea surface temperature, unlike the pattern documented for Northern Hemisphere mollusks. Direct sampling of soft bottom communities along the gradient suggests that regional trends in species richness are produced by increased alpha diversity, and not only by artifacts produced by the increase in sampling area. We hypothesize that increased shelf area south of 42°S, geographic isolation produced by divergence of major oceanic currents, and the existence of refugia during glaciations, enabled species diversification. Radiation could have been limited by narrow continental shelves between 10°,42°. Asymmetries in latitudinal diversity trends between hemispheres show that there is not a single general factor determining large-scale diversity patterns. [source] Influence of contamination by organochlorine pesticides and polychlorinated biphenyls on the breeding of the Spanish Imperial Eagle (Aquila adalberti)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2008Mauro Hernández Abstract We evaluated temporal and regional trends of organochlorine (OC) pesticide (including polychlorinated biphenyl [PCB]) levels in eggs of the Spanish Imperial Eagle (Aquila adalberti) collected in Spain between 1972 and 2003. Levels of p,p,-dichlorodiphenyldichloroethylene (DDE) and PCBs varied significantly (p = 0.022) among regions (central, western, and Doñana), being higher in Doñana than in the central and western populations (DDE: 1.64 ± 5.56, 0.816 ± 1.70, and 1.1 ± 2.66 ,g/g, respectively; PCBs: 1.189 ± 5.0, 0.517 ± 1.55, and 0.578 ± 1.75 ,g/g, respectively). Levels of DDE decreased with time, but a significant interaction was observed between region and time. In Doñana, egg volume and breadth as well as Ratcliffe Index were significantly lower after DDT use (p = 0.0018) than during the pre-DDT period (p = 0.0018); eggs were significantly smaller overall than in the other two regions (p = 0.04) and were smaller when DDE levels increased, even when controlling for regional differences (p = 0.04). Productivity in Doñana was significantly lower than in the other regions (p < 0.001). Clutch size in Doñana varied according to DDE concentrations (p = 0.01), with the highest DDE concentrations found in clutches consisting of one egg. When considering eggs with DDE levels greater than 3.5 ,g/g, a significant effect of DDE on fertility was found (p = 0.03). Clutches with DDE levels greater than 4.0 ,g/g had a higher probability of hatching failure (p = 0.07) and produced fewer fledglings (p = 0.03). If we consider 3.5 ,g/g as the lowest-observable-adverse-effect level, the proportion of sampled clutches that exceeded that level in Doñana (29%) was significantly higher than in other regions (p < 0.001). These eggs showed a mean percentage of thinning of 16.72%. Contamination by OCs, mainly DDE, could explain, at least in part, the low productivity of the Spanish Imperial Eagles in Doñana. [source] Assessment of salmon stocks and the use of management targets; a case study of the River Tamar, EnglandFISHERIES MANAGEMENT & ECOLOGY, Issue 1 2007K. HENDRY Abstract, Over recent years the rod and net catch of Atlantic salmon, Salmo salar L., on the River Tamar in south-west England has decreased markedly, resulting in a consistent failure to meet the minimum egg deposition target (conservation limit). Compliance with the target is by annual assessment using rod catch as the major input variable. Further analysis suggested a disproportionate deterioration in the rod fishery performance of the Tamar compared with rivers locally, regionally and nationally. A concomitant decrease in rod licence sales and fishing effort, above both national and regional trends was also evident. However, examination of juvenile electric fishing and adult fish counter data revealed a different trend for the past 10 years, indicating a stable fish population, albeit at a lower level of abundance than previously. The analyses suggested that without consideration of changes in effort and rod exploitation rate, rod catch alone is not a reliable indicator of stock abundance and hence should not be used as such in stock assessment. [source] Loss of forb diversity in relation to nitrogen deposition in the UK: regional trends and potential controlsGLOBAL CHANGE BIOLOGY, Issue 10 2006CARLY J. STEVENS Abstract In this study we investigate the impact of nitrogen (N) deposition on the diversity of three different vegetation functional groups , forbs, grasses and mosses , using a field survey of acid grasslands across Great Britain. Our aim is to identify the vegetation types that are most vulnerable to enhanced N deposition, and to shed light on the mechanisms that may be driving N-initiated species changes in the UK. Sixty-eight randomly selected grasslands belonging to the UK National Vegetation Classification group U4 (Festuca ovina,Agrostis capillaris,Galium saxatile grassland) were studied along a gradient of atmospheric N deposition ranging from 6 to 36 kg N ha,1 yr,1. At each site, vegetation was surveyed and samples were taken from the topsoil and subsoil. Aboveground plant material was collected from three species: a forb, grass and moss. Both the species richness and cover of forbs declined strongly with increasing N deposition, from greater than eight species/20% cover per m2 quadrat at low levels of N to fewer than two species/5% cover at the highest N deposition levels. Grasses showed a weak but significant decline in species richness, and a trend toward increasing cover with increasing N input. Mosses showed no trends in either species richness or cover. Most of the decline in plant species richness could be accounted for by the level of ammonium deposition. Soil KCl-extractable ammonium concentration showed a significant positive correlation with N input, but there was no relationship between N deposition and extractable nitrate. In the soil O/A horizon, there was no relationship between N deposition and %N, and only a very weak positive relationship between the level of N deposition and the C : N ratio. Finally, in the vegetation, there was no relationship between N deposition and either shoot tissue N concentration or N : P ratio for any of the three reference species. Combining our regional survey with the results of published N-addition experiments provides compelling evidence that there has been a significant decline in the species richness and cover of forbs across Great Britain, and that the primary cause is competition due to an increase in the cover of grasses in response to enhanced deposition of reactive N, primarily NH4+. [source] Lifestyle, occupation, and whole bone morphology of the pre-Hispanic Maya coastal population from Xcambó, Yucatan, MexicoINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 3 2007Isabel S. Wanner Abstract The present bioarchaeological study examines the external diaphyseal geometric properties of humeri, radii, femora and tibiae of the Classic period skeletal population of Xcambó, Yucatan, Mexico. The diaphysial proportions are evaluated using a biomechanical approach together with data from the material context and other osteological information. Our intent is to provide new answers to questions concerning lifestyle, domestic labour division and subsistence strategies of this coastal Maya settlement that was inhabited from the Late and Terminal Preclassic (300 BC,350 AD) to the Postclassic Period (900,1500 AD). Our results provide evidence for a marked sexual division of labour when compared with values from contemporaneous inland populations. The overall male and female loading patterns differ remarkably in terms of form and in bilateral comparison. A high directional asymmetry in the upper limbs is evident among males, a condition related to maritime transportation and trading activities. On the other hand, female upper limbs are characterized by very low side differences. Forces on the arms of women were probably dominated by food processing, in particular the grinding of grains or seeds. In the lower limbs, males show significantly higher anteroposterior bending strengths, which can be explained by greater engagement in transportation tasks and carrying heavy loads. In the course of the Classic period (350,900 AD), diachronic changes affect the male sample only, which suggests a shift of occupational pattern and physical demands. This shift, in turn, reflects Xcambó's changing role as the centre of a densifying settlement area and its place in the trading activities of northern Yucatan. Other topics of discussion relate to general regional trends and local prehispanic subsistence strategies. Our conclusions emphasize the value of geometric long bone analysis in the reconstruction of activity patterns and lifestyles in ancient coastal settlements. Copyright © 2007 John Wiley & Sons, Ltd. [source] Stream Restoration in the Upper Midwest, U.S.A.RESTORATION ECOLOGY, Issue 4 2006Gretchen G. Alexander Abstract Restoration activities intended to improve the condition of streams and rivers are widespread throughout the Upper Midwest, U.S.A. As with other regions, however, little information exists regarding types of activities and their effectiveness. We developed a database of 1,345 stream restoration projects implemented from the years 1970 to 2004 for the states of Michigan, Ohio, and Wisconsin in order to analyze regional trends in goals, presence of monitoring, spatial distribution, size, and cost of river restoration projects. We found that data on individual projects were fragmented across multiple federal, state, and county agencies, as well as nonprofit groups and consulting firms. The most common restoration goals reported for this region were in-stream habitat improvement, bank stabilization, water-quality management, and dam removal. The former two were most common in Michigan and Wisconsin, where salmonid fisheries enhancement appeared to be an important concern, whereas water-quality management was most frequent in Ohio. The most common restoration activities were the use of sand traps and riprap, and other common activities were related to the improvement of fish habitat. The median cost was $12,957 for projects with cost data, and total expenditures since 1990 were estimated at $444 million. Over time, the cost of individual projects has increased, whereas the median size has decreased, suggesting that restoration resources are being spent on smaller, more localized, and more expensive projects. Only 11% of data records indicated that monitoring was performed, and more expensive projects were more likely to be monitored. Standardization of monitoring and record keeping and dissemination of findings are urgently needed to ensure that dollars are well spent and restoration effectiveness is maximized. 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