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Showing items 1 through 9 of 38.
  1. 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.

  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, 2007
    United States of America

    We examine the incentives of atomistic producers to differentiate and collectively market products. We analyze market and welfare effects of alternative producer organizations, discuss circumstances under which they will evolve, and describe implications for the ongoing debate between the EU and the United States. As fixed costs of development and marketing increase and the anticipated market size falls, it becomes essential to increase the producer organization's ability to control supply to cover the fixed costs associated with the introduction of differentiated products.

  4. Library Resource
    Journal Articles & Books
    December, 2010
    Canada

    Feedbacks between climate warming and fire have the potential to alter Arctic and sub-Arctic vegetation. In this paper we assess the effects and interactions of temperature and wildfire on plant communities across the transition between the Arctic and sub-Arctic. Mackenzie Delta region, Northwest Territories, Canada. We sampled air temperatures, green alder (Alnus viridis ssp. fruticosa) cover, growth, reproduction and age distributions, and overall plant community composition on burned and unburned sites across a latitudinal gradient.

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

    Accurate assessment of changing fire regimes is important, since climatic change and people may be promoting more wildfires. Government wildland fire policies and restoration programmes in dry western US forests are based on the hypothesis that high‐severity fire was rare in historical fire regimes, modern fire severity is unnaturally high and restoration efforts should focus primarily on thinning forests to eliminate high‐severity fire.

  6. Library Resource
    Journal Articles & Books
    December, 2011
    Canada

    Drought-induced, regional-scale dieback of forests has emerged as a global concern that is expected to escalate under model projections of climate change. Since 2000, drought of unusual severity, extent, and duration has affected large areas of western North America, leading to regional-scale dieback of forests in the southwestern US. We report on drought impacts on forests in a region farther north, encompassing the transition between boreal forest and prairie in western Canada.

  7. Library Resource
    Journal Articles & Books
    December, 2009
    Canada

    We investigated whether accounting for land cover could improve bioclimatic models for eight species of anurans and three species of turtles at a regional scale. We then tested whether accounting for spatial autocorrelation could significantly improve bioclimatic models after statistically controlling for the effects of land cover. Nova Scotia, eastern Canada. Species distribution data were taken from a recent (1999-2003) herpetofaunal atlas. Generalized linear models were used to relate the presence or absence of each species to climate and land-cover variables at a 10-km resolution.

  8. Library Resource
    Journal Articles & Books
    December, 2014
    Canada

    Conservation programs often manage populations indirectly through the landscapes in which they live. Empirically, linking reproductive success with landscape structure and anthropogenic change is a first step in understanding and managing the spatial mechanisms that affect reproduction, but this link is not sufficiently informed by data. Hierarchical multistate occupancy models can forge these links by estimating spatial patterns of reproductive success across landscapes.

  9. Library Resource
    Journal Articles & Books
    December, 2015
    United States of America

    Reforestation of formerly cultivated land is widely understood to accumulate above‐ and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above‐ and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0–7.5 cm) were offset by significant SOM losses in subsoils (35–60 cm).

  10. Library Resource
    Journal Articles & Books
    December, 2015
    Northern America

    AIM: Deterministic niche theory predicts that increasing environmental heterogeneity increases species richness. In contrast, a recent stochastic model suggests that heterogeneity has a unimodal effect on species richness since high levels of heterogeneity reduce the effective area available per species, thereby increasing the likelihood of stochastic extinction (the ‘area–heterogeneity trade‐off’). We tested these contrasting predictions using data on bird distributions in North America. LOCATION: North America.

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