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Lower Productivity (lower + productivity)
Selected AbstractsPaleoindian environmental change and landscape response in Barger Gulch, Middle Park, ColoradoGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2005James H. Mayer Middle Park, a high-altitude basin in the Southern Rocky Mountains of north-central Colorado, contains at least 59 known Paleoindian localities. At Barger Gulch Locality B, an extensive Folsom assemblage (,10,500 14C yr B.P.) occurs within a buried soil. Radiocarbon ages of charcoal and soil organic matter, as well as stratigraphic positions of artifacts, indicate the soil is a composite of a truncated, latest-Pleistocene soil and a younger mollic epipedon formed between ,6000 and 5200 14C yr B.P. and partially welded onto the older soil following erosion and truncation. Radiocarbon ages from an alluvial terrace adjacent to the excavation area indicate that erosion followed by aggradation occurred between ,10,200 and 9700 14C yr B.P., and that the erosion is likely related to truncation of the latest-Pleistocene soil. Erosion along the main axis of Barger Gulch occurring between ,10,000 and 9700 14C yr B.P. was followed by rapid aggradation between ,9700 and 9550 14C yr B.P., which, along with the erosion at Locality B, coincides with the abrupt onset of monsoonal precipitation following cooling in the region ,11,000,10,000 14C yr B.P. during the Younger Dryas oscillation. Buried soils dated between ,9500 and 8000 14C yr B.P. indicate relative landscape stability and soil formation throughout Middle Park. Morphological characteristics displayed by early Holocene soils suggest pedogenesis under parkland vegetation in areas currently characterized by sagebrush steppe. The expansion of forest cover into lower elevations during the early Holocene may have resulted in lower productivity in regards to mammalian fauna, and may partly explain the abundance of early Paleoindian sites (,11,000,10,000 14C yr B.P., 76%) relative to late Paleoindian sites (,10,000,8000 14C yr B.P., 24%) documented in Middle Park. © 2005 Wiley Periodicals, Inc. [source] Avian productivity in urban landscapes: a review and meta-analysisIBIS, Issue 1 2009D. E. CHAMBERLAIN There is an urgent need to thoroughly review and comprehend the effects of urbanization on wildlife in order to understand both the ecological implications of increasing urbanization and how to mitigate its threat to biodiversity globally. We examined patterns in comparative productivity of urban and non-urban passerine birds, using published estimates from paired comparisons, and by reviewing and developing explanations in terms of resources, competitors, predators and other specifically urban environmental factors. The most consistent patterns were for earlier lay dates, lower clutch size, lower nestling weight and lower productivity per nesting attempt in urban landscapes; these were supported by a formal meta-analysis. Nest failure rates did not show consistent patterns across the species considered. We suggest that food availability is a key driver of differences in passerine demography between landscapes. In urban habitats, human-provided food may improve adult condition over winter, leading to earlier lay dates and, in some species, to higher survival and higher breeding densities, but paucity of natural food may lead to lower productivity per nesting attempt. We demonstrate that additional comparative research is needed on a wider range of species, on the effects of natural and human-provided food availability, and on the differences in survival and dispersal between urban and non-urban populations. Importantly, better-targeted research and monitoring is needed in areas that are at greatest threat from urbanization, especially in the developing world. [source] Site productivity and plant size explain the response of annual species to grazing exclusion in a Mediterranean semi-arid rangelandJOURNAL OF ECOLOGY, Issue 2 2004Yagil Osem Summary 1The response of an annual plant community to protection from grazing as a function of variation in site productivity was studied in a semi-arid Mediterranean rangeland in Israel over 4 years (1996,99). The abundance of species was compared in grazed vs. ungrazed plots (exclosures) in four neighbouring topographic sites (south- and north-facing slopes, hilltop and Wadi shoulders), representing a gradient of resource availability and productivity. 2Above-ground potential productivity at peak standing crop in spring (i.e. inside exclosures) varied considerably between years and topographic sites. Productivity was similar among the hilltop, south- and north-facing slopes, and was typical of semi-arid ecosystems (10,200 g,2). Productivity in the Wadi was consistently greater (up to 700 g,2) and reached the range of subhumid grassland ecosystems. 3The effect of grazing exclusion on the composition of the annual vegetation was productivity-dependent. Lower similarity (Sorenson's quantitative similarity index) between grazed and ungrazed subplots was observed in the productive Wadi compared with the less productive sites. The small-scale variation in grazing impact on species composition, due to differences in productivity, is consistent with models predicting similar trends in perennial grasslands across larger scale gradients. 4The relationship between plant size (above-ground dry-weight), site productivity and response to fencing was analysed for the 36 most abundant annual species. Large species were more abundant in more productive sites, and small species at lower productivity, although few species were restricted to particular productivity levels. The response of individual species to protection from grazing was productivity dependent, with plant size playing a central role. Larger species tended to increase and small ones to decrease in abundance after fencing, with a mixed response in species with intermediate size. 5A conceptual model is presented relating the response to protection from grazing along gradients of productivity to species plant size. [source] Changing marine productivity off northern Chile during the past 19,000 years: a multivariable approachJOURNAL OF QUATERNARY SCIENCE, Issue 4 2004M. Mohtadi Abstract A multivariable approach utilising bulk sediment, planktonic Foraminifera and siliceous phytoplankton has been used to reconstruct rapid variations in palaeoproductivity in the Peru,Chile Current System off northern Chile for the past 19,000,cal.,yr. During the early deglaciation (19,000,16,000,cal.,yr,BP), our data point to strongest upwelling intensity and highest productivity of the past 19,000,cal.,yr. The late deglaciation (16,000,13,000,cal.,yr,BP) is characterised by a major change in the oceanographic setting, warmer water masses and weaker upwelling at the study site. Lowest productivity and weakest upwelling intensity are observed from the early to the middle Holocene (13,000,4000,cal.,yr,BP), and the beginning of the late Holocene (<4000,cal.,yr,BP) is marked by increasing productivity, mainly driven by silicate-producing organisms. Changes in the productivity and upwelling intensity in our record may have resulted from a large-scale compression and/or displacement of the South Pacific subtropical gyre during more productive periods, in line with a northward extension of the Antarctic Circumpolar Current and increased advection of Antarctic water masses with the Peru,Chile Current. The corresponding increase in hemispheric thermal gradient and wind stress induced stronger upwelling. During the periods of lower productivity, this scenario probably reversed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Estimating net primary production of boreal forests in Finland and Sweden from field data and remote sensingJOURNAL OF VEGETATION SCIENCE, Issue 2 2004Daolan Zheng We calculated annual mean stem volume increment (AMSVI) and total litter fall to produce forest net primary production (NPP) maps at 1-km2 and half-degree resolutions in Finland and Sweden. We used a multi-scale methodology to link field inventory data reported at plot and forestry district levels through a remotely sensed total plant biomass map derived from 1-km2 AVHRR image. Total litter fall was estimated as function of elevation and latitude. Leaf litter fall, a surrogate for fine root production, was estimated from total litter fall by forest type. The gridded NPP estimates agreed well with previously reported NPP values, based on point measurements. Regional NPP increases from northeast to southwest. It is positively related to annual mean temperature and annual mean total precipitation (strongly correlated with temperature) and is negatively related to elevation at broad scale. Total NPP (TNPP) values for representative cells selected based on three criteria were highly correlated with simulated values from a process-based model (CEVSA) at 0.5° × 0.5° resolution. At 1-km2 resolution, mean above-ground NPP in the region was 408 g/m2/yr ranging from 172 to 1091 (standard deviation (SD) = 134). Mean TNPP was 563 (252 to 1426, SD = 176). Ranges and SD were reduced while the mean values of the estimated NPP stayed almost constant as cell size increased from 1-km2 to 0.5° × 0.5°, as expected. Nordic boreal forests seem to have lower productivity among the world boreal forests. [source] Corruption, Productivity and SocialismKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 2 2003Geoffrey Wyatt Summary The level of productivity is correlated across countries with measures of (lack of) corruption, but this appears to be due to a common association of these variables with measures of civil infrastructure, here measured by a combination of governance indexes labelled ,rule of law' and ,government effectiveness'. New instruments based on the size- and spatial-distributions of cities within the countries of the world were constructed in order to explore the causal relationships between civil infrastructure and productivity. Civil infrastructure accounts for a substantial fraction of the global variation in output per worker across countries. Within this empirical pattern there is a systematic deviation associated with the current and former socialist states, which have both lower productivity and inferior civil infrastructure than would be predicted for otherwise similar non-socialist states. However, for a given level of the index of civil infrastructure these states are also shown to have a higher level of productivity than otherwise similar non-socialist states. The unconditionally low productivity of socialist states is attributed entirely to the indirectly deleterious effects that socialism had on civil infrastructure, which more than offset its directly positive effect on output. [source] Effect of agro-forestry and landscape changes on common buzzards (Buteo buteo) in the Alps: implications for conservationANIMAL CONSERVATION, Issue 1 2005Fabrizio Sergio In Italy, pre-Alpine forests, once managed through coppice silviculture, are being converted to mature woodland, while land abandonment is causing woodland expansion and erosion of open habitats. Based on habitat-selection analyses, we predicted the impact of such changes on common buzzards (Buteo buteo), which depend on forested and open areas for nesting and foraging. Compared to availability, at a micro-scale buzzards selected nests higher above ground and on trees frequently covered by ivy. At the landscape-scale, buzzards avoided roads and conspecifics, while selecting rugged areas with high habitat heterogeneity, probably related to a varied food supply. Productivity was related to the availability of arid habitats, probably because of their richness in main prey species. Finally, population density was negatively related to the abundance of eagle owls (Bubo bubo), a potential predator of adults and nestlings, and positively related to the availability of woodland, a low predation-risk habitat rich in food and nest-sites. Therefore, buzzard settlement, density and productivity depended on the complex interplay of food availability, human persecution and predation risk. Thus, the current landscape changes would benefit buzzards by providing more nest-sites, but would be detrimental because of the lower productivity associated with the disappearance of dry open areas. Proposed conservation guidelines focus on conversion of coppice woodland to mature forests and active management of dry heath, a conservation sensitive habitat, through controlled burning. [source] R&D INVESTMENTS AND SEQUENTIAL WAGE NEGOTIATIONS,AUSTRALIAN ECONOMIC PAPERS, Issue 3 2009JUAN CARLOS BÁRCENA-RUIZ This paper analyses how the structure of wage bargaining affects R&D investment by firms that increases the productivity of labour in a Cournot duopoly. We find that total expenditure on R&D is greater when wages are set simultaneously than when they are set sequentially. Thus sequential wage negotiations reduce the incentive for firms to innovate and affect the productivity of labour. When wage negotiations are sequential the productivity of labour is greater (lower) in the follower (leader) firm than when negotiations are simultaneous. We also obtain that for same parameter values it is possible for the firm with the lower productivity to end up paying a higher wage than the firm with the higher level of labour productivity. [source] | ||||||||||||||||