101 resultados para Birds of prey in a changing environment


Relevância:

100.00% 100.00%

Publicador:

Resumo:

The development of architecture and the settlement is central to discussions concerning the Neolithic transformation asthe very visible evidence for the changes in society that run parallel to the domestication of plants and animals. Architecture hasbeen used as an important aspect of models of how the transformation occurred, and as evidence for the sharp difference betweenhunter-gatherer and farming societies. We suggest that the emerging evidence for considerable architectural complexity from theearly Neolithic indicates that some of our interpretations depend too much on a very basic understanding of structures which arenormally seen as being primarily for residential purposes and containing households, which become the organising principle for thenew communities which are often seen as fully sedentary and described as villages. Recent work in southern Jordan suggests that inthis region at least there is little evidence for a standard house, and that structures are constructed for a range of diverse primary purposes other than simple domestic shelters.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The majority of the world’s population now live in cities. This poses great challenges, but also great opportunities in terms of tackling climate change, resource depletion and environmental degradation. Policy agendas have increasingly focused on how to develop and maintainintegrated sustainable urban development’, and a number of theoretical conceptualisations of urban transition have been formulated to help our thinking and understanding in both developed and developing countries. Drawing on examples around the world the paper aims to examine the key ‘critical success factors’ that need to be in place for cities to traverse a pathway to a more sustainable future in urban development terms by 2050. The paper explores how important the issues of ‘scale’ is in the context of complexity and fragmentation in the city’s built environment, identifies the lessons that can be learned for future sustainable urban development, and the further research which is needed to address future urban transitions to 2050.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

In Situ preservation is a core strategy for the conservation and management of waterlogged remains at wetland sites. Inorganic and organic remains can, however, quickly become degraded, or lost entirely, as a result of chemical or hydrological changes. Monitoring is therefore crucial in identifying baseline data for a site, the extent of spatial and or temporal variability, and in evaluating the potential impacts of these variables on current and future In Situ preservation potential. Since August 2009, monthly monitoring has taken place at the internationally important Iron Age site of Glastonbury Lake Village in the Somerset Levels, UK. A spatial, stratigraphic, and analytical approach to the analysis of sediment horizons and monitoring of groundwater chemistry, redox potential, water table depth and soil moisture (using TDR) was used to characterize the site. Significant spatial and temporal variability has been identified, with results from water-table monitoring and some initial chemical analysis from Glastonbury presented here. It appears that during dry periods parts of this site are at risk from desiccation. Analysis of the chemical data, in addition to integrating the results from the other parameters, is ongoing, with the aim of clarifying the risk to the entire site.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Resetting of previously accumulated optically stimulated luminescence (OSL) signals during transport of sediment is a fundamental requirement for reliable optical dating. The completeness of optical resetting of 46 modern-age quartz samples from a variety of depositional environments was examined. All equivalent dose (De) estimates were View the MathML source, with the majority of aeolian samples View the MathML source, and fluvial samples View the MathML source. The OSL signal of quartz originates from several trap types with different rates of charge loss during illumination. As such, incomplete bleaching may be identifiable as an increase in De from easy-to-bleach through to hard-to-bleach components. For all modern fluvial samples with non-zero De values, SAR De(t) analysis and component-resolved linearly modulated OSL (LM OSL) De estimates showed this to be the case, implying incomplete resetting of previously accumulated charge. LM OSL measurements were also made to investigate the extent of bleaching of the slow components in the natural environment. In aeolian sediments examined, the natural LM OSL was effectively zero (i.e. all components were fully reset). The slow components of modern fluvial samples displayed measurable residual signals up to 15 Gy.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Sensible heat fluxes (QH) are determined using scintillometry and eddy covariance over a suburban area. Two large aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 km and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 km2, whilst the long path extends from the rural outskirts to the town centre and has a source area of around 5-10 km2. These large-scale heat fluxes are compared with local-scale eddy covariance measurements. Clear seasonal trends are revealed by the long duration of this dataset and variability in monthly QH is related to the meteorological conditions. At shorter time scales the response of QH to solar radiation often gives rise to close agreement between the measurements, but during times of rapidly changing cloud cover spatial differences in the net radiation (Q*) coincide with greater differences between heat fluxes. For clear days QH lags Q*, thus the ratio of QH to Q* increases throughout the day. In summer the observed energy partitioning is related to the vegetation fraction through use of a footprint model. The results demonstrate the value of scintillometry for integrating surface heterogeneity and offer improved understanding of the influence of anthropogenic materials on surface-atmosphere interactions.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Building Information Modeling (BIM) is the process of structuring, capturing, creating, and managing a digital representation of physical and/or functional characteristics of a built space [1]. Current BIM has limited ability to represent dynamic semantics, social information, often failing to consider building activity, behavior and context; thus limiting integration with intelligent, built-environment management systems. Research, such as the development of Semantic Exchange Modules, and/or the linking of IFC with semantic web structures, demonstrates the need for building models to better support complex semantic functionality. To implement model semantics effectively, however, it is critical that model designers consider semantic information constructs. This paper discusses semantic models with relation to determining the most suitable information structure. We demonstrate how semantic rigidity can lead to significant long-term problems that can contribute to model failure. A sufficiently detailed feasibility study is advised to maximize the value from the semantic model. In addition we propose a set of questions, to be used during a model’s feasibility study, and guidelines to help assess the most suitable method for managing semantics in a built environment.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Possible future changes of clustering and return periods (RPs) of European storm series with high potential losses are quantified. Historical storm series are identified using 40 winters of reanalysis. Time series of top events (1, 2 or 5 year return levels (RLs)) are used to assess RPs of storm series both empirically and theoretically. Additionally, 800 winters of general circulation model simulations for present (1960–2000) and future (2060–2100) climate conditions are investigated. Clustering is identified for most countries, and estimated RPs are similar for reanalysis and present day simulations. Future changes of RPs are estimated for fixed RLs and fixed loss index thresholds. For the former, shorter RPs are found for Western Europe, but changes are small and spatially heterogeneous. For the latter, which combines the effects of clustering and event ranking shifts, shorter RPs are found everywhere except for Mediterranean countries. These changes are generally not statistically significant between recent and future climate. However, the RPs for the fixed loss index approach are mostly beyond the range of pre-industrial natural climate variability. This is not true for fixed RLs. The quantification of losses associated with storm series permits a more adequate windstorm risk assessment in a changing climate.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Studies of climate change impacts on the terrestrial biosphere have been completed without recognition of the integrated nature of the biosphere. Improved assessment of the impacts of climate change on food and water security requires the development and use of models not only representing each component but also their interactions. To meet this requirement the Joint UK Land Environment Simulator (JULES) land surface model has been modified to include a generic parametrisation of annual crops. The new model, JULES-crop, is described and evaluation at global and site levels for the four globally important crops; wheat, soybean, maize and rice. JULES-crop demonstrates skill in simulating the inter-annual variations of yield for maize and soybean at the global and country levels, and for wheat for major spring wheat producing countries. The impact of the new parametrisation, compared to the standard configuration, on the simulation of surface heat fluxes is largely an alteration of the partitioning between latent and sensible heat fluxes during the later part of the growing season. Further evaluation at the site level shows the model captures the seasonality of leaf area index, gross primary production and canopy height better than in the standard JULES. However, this does not lead to an improvement in the simulation of sensible and latent heat fluxes. The performance of JULES-crop from both an Earth system and crop yield model perspective is encouraging. However, more effort is needed to develop the parametrisation of the model for specific applications. Key future model developments identified include the introduction of processes such as irrigation and nitrogen limitation which will enable better representation of the spatial variability in yield.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Eddy covariance has been used in urban areas to evaluate the net exchange of CO2 between the surface and the atmosphere. Typically, only the vertical flux is measured at a height 2–3 times that of the local roughness elements; however, under conditions of relatively low instability, CO2 may accumulate in the airspace below the measurement height. This can result in inaccurate emissions estimates if the accumulated CO2 drains away or is flushed upwards during thermal expansion of the boundary layer. Some studies apply a single height storage correction; however, this requires the assumption that the response of the CO2 concentration profile to forcing is constant with height. Here a full seasonal cycle (7th June 2012 to 3rd June 2013) of single height CO2 storage data calculated from concentrations measured at 10 Hz by open path gas analyser are compared to a data set calculated from a concurrent switched vertical profile measured (2 Hz, closed path gas analyser) at 10 heights within and above a street canyon in central London. The assumption required for the former storage determination is shown to be invalid. For approximately regular street canyons at least one other measurement is required. Continuous measurements at fewer locations are shown to be preferable to a spatially dense, switched profile, as temporal interpolation is ineffective. The majority of the spectral energy of the CO2 storage time series was found to be between 0.001 and 0.2 Hz (500 and 5 s respectively); however, sampling frequencies of 2 Hz and below still result in significantly lower CO2 storage values. An empirical method of correcting CO2 storage values from under-sampled time series is proposed.