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Showing items 1 through 9 of 367.
  1. Library Resource
    Journal Articles & Books
    December, 2010

    Estimates of the percent of Earth's land surface that has either been transformed or degraded by human activity range between 39 and 50 percent, with agriculture accounting for the vast majority of these changes. Although much of the focus of research on land use and cover change in the tropics has been on deforestation, ongoing socioeconomic changes both locally and globally have made land transitions in the tropics extremely fluid. In addition, feedbacks between land cover change and human behavior constrain the extent and trajectories of land transitions.

  2. Library Resource
    Journal Articles & Books
    December, 2012
    United States of America

    1. Little is known about the diversity and land management response of native solitary bees in globally rare barrens restricted to the northeastern United States. Herein we assess solitary bee diversity in a scrub oak barrens 2 years after a mow and herbicide treatment. 2. Standard bowl‐trap and sweep‐net surveys were repeated six times during June–August in four treated scrub oak patches and a nearby untreated scrub oak patch. 3. Bee richness and total abundance (all specimens) did not differ appreciably between the treated and untreated scrub oak.

  3. Library Resource
    Journal Articles & Books
    December, 2012

    1. Arctic vegetation tends to be spatially heterogeneous and can have large areas of mixed ‘transition zone’ vegetation between stands dominated by a single or few species. If plant photosynthesis and growth within these transition zones differs significantly from main vegetation stands, and if transition zones are not considered when extrapolating stand‐level findings to larger scales in space, then transition zones will provide considerable error to landscape‐level estimates of gross primary productivity (GPP).

  4. Library Resource
    Journal Articles & Books
    December, 2014
    United States of America, Northern America

    AIM: The geographical expansion of white‐winged doves (Zenaida asiatica) in North America has attracted the attention of biologists and sportsmen because of their recreational and aesthetic value; however, data on factors driving the spatial spread of this species are lacking. We examined spatial and temporal patterns of range expansion for white‐winged doves along the northern edge of their geographical range from 1979 to 2007 and used a dynamic occupancy model to estimate when and where doves would be found along an expansion gradient. LOCATION: Southern half of the USA.

  5. Library Resource
    Journal Articles & Books
    December, 2007
    Tanzania

    Livestock encroachment is threatening the populations of large wild mammals in Tanzania. Competition for quality grazing land by domestic stocks is one of the main factors impacting wild species during this encroachment. In the Kilombero Game Controlled Area (KGCA), extensive livestock husbandry is negatively associated with wildlife populations, especially outside the hunting season. This study assessed the relationship between livestock number and the abundance of three wild species: puku, buffalo and elephant.

  6. Library Resource
    Journal Articles & Books
    December, 2007
    Australia

    Offsets (also known as mitigation banks, compensatory habitat, set-asides) is a policy instrument recently introduced in several States in Australia to permit some land clearing while striving for no net loss in the extent and condition of native vegetation overall. Offsetting is criticized with respect to the amount of gain required to compensate for losses from clearing, the equivalence of losses and gains, the time lag between losses and gains and a poor record of compliance.

  7. Library Resource
    Journal Articles & Books
    December, 2006

    This article examines economic efficiency (EE) of crop production of Russian corporate farms for 1993-1998. EE declined over the period, due to declines in both technical and allocative efficiency. Technical efficiency (TE) results indicate that output levels could have been maintained while reducing overall input use by an average of 29-31% in 1998, depending on the method used, while the allocative efficiency (AE) results show that costs could have been reduced about 30%.

  8. Library Resource
    Journal Articles & Books
    December, 2015

    Projections of the response of crop yield to climate change at different spatial scales are known to vary. However, understanding of the causes of systematic differences across scale is limited. Here, we hypothesize that heterogeneous cropping intensity is one source of scale dependency. Analysis of observed global data and regional crop modelling demonstrate that areas of high vs. low cropping intensity can have systematically different yields, in both observations and simulations.

  9. Library Resource
    Journal Articles & Books
    December, 2015
    China

    Organic carbon (OC) sequestration in degraded semi‐arid environments by improved soil management is assumed to contribute substantially to climate change mitigation. However, information about the soil organic carbon (SOC) sequestration potential in steppe soils and their current saturation status remains unknown. In this study, we estimated the OC storage capacity of semi‐arid grassland soils on the basis of remote, natural steppe fragments in northern China. Based on the maximum OC saturation of silt and clay particles

  10. Library Resource
    Journal Articles & Books
    December, 2015
    Finland

    Quantifying landscape‐scale methane (CH₄) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH₄ emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH₄ uptake, in controlling landscape‐level fluxes.

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