763,232 research outputs found

    Diffusion-driven instabilities and emerging spatial patterns in patchy landscapes

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    Spatial variation in population densities across a landscape is a feature of many ecological systems, from self-organised patterns on mussel beds to spatially restricted insect outbreaks. It occurs as a result of environmental variation in abiotic factors and/or biotic factors structuring the spatial distribution of populations. However the ways in which abiotic and biotic factors interact to determine the existence and nature of spatial patterns in population density remain poorly understood. Here we present a new approach to studying this question by analysing a predator–prey patch-model in a heterogenous landscape. We use analytical and numerical methods originally developed for studying nearest- neighbour (juxtacrine) signalling in epithelia to explore whether and under which conditions patterns emerge. We find that abiotic and biotic factors interact to promote pattern formation. In fact, we find a rich and highly complex array of coexisting stable patterns, located within an enormous number of unstable patterns. Our simulation results indicate that many of the stable patterns have appreciable basins of attraction, making them significant in applications. We are able to identify mechanisms for these patterns based on the classical ideas of long-range inhibition and short-range activation, whereby landscape heterogeneity can modulate the spatial scales at which these processes operate to structure the populations

    Lines and patterns in the Frisian landscape

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    Valuing Natural Space and Landscape Fragmentation in Richmond, VA

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    Hedonic pricing methods and GIS (Geographic Information Systems) were used to evaluate relationships between sale price of single family homes and landscape fragmentation and natural land cover. Spatial regression analyses found that sale prices increase as landscapes become less fragmented and the amount of natural land cover around a home increases. The projected growth in population and employment in the Richmond, Virginia region and subsequent increases in land development and landscape fragmentation presents a challenge to sustaining intact healthy ecosystems in the Richmond region. Spatial regression analyses helped illuminate how land cover patterns influence sale prices and landscape patterns that are economically and ecologically advantageous

    Gravity model explained by the radiation model on a population landscape

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    Understanding the mechanisms behind human mobility patterns is crucial to improve our ability to optimize and predict traffic flows. Two representative mobility models, i.e., radiation and gravity models, have been extensively compared to each other against various empirical data sets, while their fundamental relation is far from being fully understood. In order to study such a relation, we first model the heterogeneous population landscape by generating a fractal geometry of sites and then by assigning to each site a population independently drawn from a power-law distribution. Then the radiation model on this population landscape, which we call the radiation-on-landscape (RoL) model, is compared to the gravity model to derive the distance exponent in the gravity model in terms of the properties of the population landscape, which is confirmed by the numerical simulations. Consequently, we provide a possible explanation for the origin of the distance exponent in terms of the properties of the heterogeneous population landscape, enabling us to better understand mobility patterns constrained by the travel distance.Comment: 14 pages, 4 figure

    The fourth dimension in landscape analysis: changing of heritage and ecological values in the Évora cultural landscapes.

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    Time is one of the most important driving forces in Landscape Ecology. Time along with geosystem, biosystem and socialsystem determines landscape heterogeneity which reveals itself in different patterns and functions. Cultural Landscapes are the result of the interactions between man and environment along time

    Modelling and simulating change in reforesting mountain landscapes using a social-ecological framework

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    Natural reforestation of European mountain landscapes raises major environmental and societal issues. With local stakeholders in the Pyrenees National Park area (France), we studied agricultural landscape colonisation by ash (Fraxinus excelsior) to enlighten its impacts on biodiversity and other landscape functions of importance for the valley socio-economics. The study comprised an integrated assessment of land-use and land-cover change (LUCC) since the 1950s, and a scenario analysis of alternative future policy. We combined knowledge and methods from landscape ecology, land change and agricultural sciences, and a set of coordinated field studies to capture interactions and feedback in the local landscape/land-use system. Our results elicited the hierarchically-nested relationships between social and ecological processes. Agricultural change played a preeminent role in the spatial and temporal patterns of LUCC. Landscape colonisation by ash at the parcel level of organisation was merely controlled by grassland management, and in fact depended on the farmer's land management at the whole-farm level. LUCC patterns at the landscape level depended to a great extent on interactions between farm household behaviours and the spatial arrangement of landholdings within the landscape mosaic. Our results stressed the need to represent the local SES function at a fine scale to adequately capture scenarios of change in landscape functions. These findings orientated our modelling choices in the building an agent-based model for LUCC simulation (SMASH - Spatialized Multi-Agent System of landscape colonization by ASH). We discuss our method and results with reference to topical issues in interdisciplinary research into the sustainability of multifunctional landscapes

    Landscape Preferences and Patterns of Residential Development

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    I analyze a model of residential location choice in which people derive utility from their proximity to open space. When people have such landscape preferences a new residential development contains more people, more tightly packed than is optimal. More surprising, in a model where new residents arrive simultaneously, I find that land price gradients are highly non-monotonic and do correctly reflect the value of open space. On the other hand, when new residents arrive sequentially, land price gradients are nearly monotonic but do not correctly reflect the value of open space. Finally, dynamic equilibria generally have the property that more remote areas are developed before more central areas. These results have a number of interesting implications for policy. In particular; (1) the creation of central city parks is welfare improving, (2) infill development of central city open space is not welfare improving, (3) the ability of regulation to restrict development at the city s limit, greenbelts , to improve welfare does not derive from a taste for nearby open space, and (4), creating small parks in undeveloped areas before they are subject to development pressure may deter leapfrogging development. Finally, the fact that land prices need not reflect the value of open space suggests that hedonic estimates may understate the value of such open space.Sprawl, Landscape preferences.

    Analysis of urban sprawl at mega city Cairo, Egypt using multisensoral remote sensing data, landscape metrics and gradient analysis

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    This paper is intended to highlight the capabilities of synergistic usage of remote sensing, landscape metrics and gradient analysis. We aim to improve the understanding of spatial characteristics and effects of urbanization on city level. Multisensoral and multitemporal remotely sensed data sets from the Landsat and TerraSAR-X sensor enable monitoring a long time period with area-wide information on the spatial urban expansion over time. Landscape metrics aim to quantify patterns on urban footprint level complemented by gradient analysis giving insight into the spatial developing of spatial parameters from the urban center to the periphery. The results paint a characteristic picture of the emerging spatial urban patterns at mega city Cairo, Egypt since the 1970s

    Globalisation - a threat to traditional landscapes and local identity?

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    Traditional landscapes could be considered as one of the most apparent carriers of local identities. They act as memory of previous human activities. During the 1990s the economic changes have had a drastic influence on the appearance of these landscapes. On one hand, local people are keen to keep the existing patterns that indicate their feeling of belonging. On the other hand, there is a desire to introduce new patterns dictated by new technologies, economic conditions, enlarged knowledge. This might lead to a kind of standardized landscape so that one cannot distinguish between, e.g., Denmark and western Estonia. The presentation will focus on the local identities in three Estonian counties. We deal with locals' preferences and ideas concerning their landscapes. Based on some 400 interviews we try to investigate which is the role of traditional landscape in local life, what kind of landscape changes are seen by locals as acceptable, what trade-offs are possible on landscape development, how could local people be involved in landscape planning, do current economic policies support or harm the maintenance of the traditional landscape.
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