Résultats de la recherche | Land Portal

Résultats de la recherche

Showing items 1 through 9 of 372.
  1. Library Resource
    Articles et Livres
    décembre, 2014
    Allemagne

    The National Forest Soil Inventory (NFSI) provides the Greenhouse Gas Reporting in Germany with a quantitative assessment of organic carbon (C) stocks and changes in forest soils. Carbon stocks of the organic layer and the mineral topsoil (30� cm) were estimated on the basis of ca. 1.800 plots sampled from 1987 to 1992 and resampled from 2006 to 2008 on a nationwide grid of 8� � 8� km. Organic layer C stock estimates were attributed to surveyed forest stands and CORINE land cover data.

  2. Library Resource
    Articles et Livres
    décembre, 2016

    Although agriculture is amongst the world's most widespread land uses, studies of its effects on stream ecosystems are often limited in spatial extent. National monitoring data could extend spatial coverage and increase statistical power, but present analytical challenges where covarying environmental variables confound relationships of interest. Propensity modelling is used widely outside ecology to control for confounding variables in observational data.

  3. Library Resource
    Articles et Livres
    décembre, 2016

    Increasing community dissimilarity across geographic distance has been described for a wide variety of organisms and understanding its underlying causes is key to understanding mechanisms driving patterns of biodiversity. Both niche‐based and neutral processes may produce a distance decay relationship; however, disentangling their relative influence requires simultaneous examination of multiple potential drivers.

  4. Library Resource
    Articles et Livres
    décembre, 2014
    Suède

    Increasing landscape heterogeneity and organic farming practices are known to enhance species richness in agroecosystems. However, little is known about the consequences of these management options on other biodiversity components such as community composition, phylogenetic structure and functional diversity which may be more closely linked to ecosystem functioning. We surveyed semi‐natural plant communities within the uncultivated field margins of 18 arable farms in Skåne, south Sweden.

  5. Library Resource
    Articles et Livres
    décembre, 2006
    Espagne

    Question: Small and marginal forest populations are a focus of attention because of their high biodiversity value as well as the risk of population decline and loss. In this context, we ask to what extent a small, marginal Quercus suber (Cork oak) population located in the eastern Iberian Peninsula (Valencia, Spain) has the capacity for self‐regeneration and what are the factors that determine its recruitment variability. Location: Quercus suber forest in Pinet (Valencia, Spain).

  6. Library Resource
    Articles et Livres
    décembre, 2009

    Plant extinctions from urban areas are a growing threat to biodiversity worldwide. To minimize this threat, it is critical to understand what factors are influencing plant extinction rates. We compiled plant extinction rate data for 22 cities around the world. Two-thirds of the variation in plant extinction rates was explained by a combination of the city's historical development and the current proportion of native vegetation, with the former explaining the greatest variability.

  7. Library Resource
    Articles et Livres
    décembre, 2015
    Espagne

    AIM: Efforts to adapt conservation to climate change are hampered by a scarcity of studies of community‐level ecological responses. We examined temporal (40 years) and spatial (1700 m elevational gradient) variation in butterfly communities, aiming to test whether the composition of communities in terms of species' thermal envelopes tracked regional warming, and whether local habitat influenced community responses to climate variation. LOCATION: Sierra de Guadarrama (central Spain).

  8. Library Resource
    Articles et Livres
    décembre, 2014
    Europe

    AIM: Remote sensing coupled with direct observation allows recent changes in vegetation to be investigated but, in order to extend our understanding of land‐cover change further back in time, different proxies for vegetation are required. The pseudobiomization (PBM) approach has been developed to transform fossil pollen data into land‐cover classes (LCCs) in order to reconstruct broad‐scale anthropogenic land‐use change through time.

  9. Library Resource
    Articles et Livres
    décembre, 2011
    Madagascar, Kenya, Afrique

    Protected Areas (PAs) form a core component of efforts to conserve biodiversity, but are designated for a variety of reasons. We assessed the effectiveness of PAs in covering the ranges of 157 globally threatened terrestrial bird species in mainland Africa and Madagascar. To reduce commission errors, rather than using Extent of Occurrence (EOO) as a measure of distribution, we estimated the Extent of potentially Suitable Habitat (ESH) for each species within its EOO, using data on habitat preferences and land cover.

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