996 resultados para prescribed fire


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The EU’s October summit was dominated by one issue; the migration and refugee crisis, with EU leaders intent on putting on a public display of unity after weeks of bitter arguments, and concentrating on fire-fighting and immediate measures to tackle the most pressing reasons for, and impacts of, the crisis. Longer-term measures to address some of the root causes of increased migratory flows, support for the integration of newly arrived refugees or the introduction of new channels of legal migration, were not discussed. The Summit also spent little time on two issues that had originally been expected to be a key part of the agenda: the forthcoming British referendum on EU membership, where irritation with the slow pace of talks and British vagueness about its demands were in evidence; and the governance of Economic and Monetary Union (EMU), where EU leaders missed another opportunity for a thorough debate about future perspectives on the basis of the ‘Five Presidents’ Report’.

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We synthesize recent results from lake-sediment studies of Holocene fire-climate-vegetation interactions in Alaskan boreal ecosystems. At the millennial time scale, the most robust feature of these records is an increase in fire occurrence with the establishment of boreal forests dominated by Picea mariana: estimated mean fire-return intervals decreased from ≥300 yrs to as low as ∼80 yrs. This fire-vegetation relationship occurred at all sites in interior Alaska with charcoal-based fire reconstructions, regardless of the specific time of P. mariana arrival during the Holocene. The establishment of P. mariana forests was associated with a regional climatic trend toward cooler/wetter conditions. Because such climatic change should not directly enhance fire occurrence, the increase in fire frequency most likely reflects the influence of highly flammable P. mariana forests, which are more conducive to fire ignition and spread than the preceding vegetation types (tundra, and woodlands/forests dominated by Populus or Picea glauca). Increased lightning associated with altered atmospheric circulation may have also played a role in certain areas where fire frequency increased around 4000 calibrated years before present (BP) without an apparent increase in the abundance of P. mariana. When viewed together, the paleo-fire records reveal that fire histories differed among sites in the same modern fire regime and that the fire regime and plant community similar to those of today became established at different times. Thus the spatial array of regional fire regimes was non-static through the Holocene. However, the patterns and causes of the spatial variation remain largely unknown. Advancing our understanding of climate-fire-vegetation interactions in the Alaskan boreal biome will require a network of charcoal records across various ecoregions, quantitative paleoclimate reconstructions, and improved knowledge of how sedimentary charcoal records fire events.

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Jordan & Anderson, architect (1863); Spier & Rohns (1898). The old Law Building was renamed Haven Hall in 1933. It became one of the main buildings for LS&A used by Departments of History, Sociology and Journalism. The old Law Library became a study hall and Bureau of Government Library. Extension Division also had offices in Haven Hall.

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Jordan & Anderson, architect (1863); Spier & Rohns (1898). The old Law Building was renamed Haven Hall in 1933. It became one of the main buildings for LS&A used by Departments of History, Sociology and Journalism. The old Law Library became a study hall and Bureau of Government Library. Extension Division also had offices in Haven Hall.

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Jordan & Anderson, architect (1863); Spier & Rohns (1898). The old Law Building was renamed Haven Hall in 1933. It becomes one of the main buildings for LS&A used by Departments of History, Sociology and Journalism. The old Law Library became a study hall and Bureau of Government Library. Extension Division also had offices in Haven Hall.