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The ecological impacts of regional-scale drought-induced tree die-off: implications and challenges for atmospheric sciences
David D. Breshears, University of Arizona, Tucson, AZ
Drought episodes can trigger tree mortality at landscape to regional scales. Such land surface changes have important implications for climate and weather modeling. Of particular concern are feedbacks that could occur between land surface changes and climate, especially under warmer temperatures. A recent drought triggered regional scale die-off of pinyon pine (Pinus edulis) across southwestern USA, with some sites experiencing more than 90% tree mortality. Notably, the ecological impacts of the recent drought apparently were more severe than that of a previous drought in the 1905s that also triggered tree die-off: even trees in the wettest, coolest sites experienced extensive mortality during the recent drought. Compared to the 1950s drought, the recent drought was not drier but it was warmer, suggesting that increased temperatures may have exacerbated the die-off. This response could be of particular relevance to the atmospheric sciences community because 1) the die-off was extensive (>12,000 km2), 2) it will be decades, at a minimum, before a similar overstory develops again, 3) such die-off can dramatically alter key land surface characteristics such as albedo, latent heat flux, sensible heat flux, and surface roughness, and 4) future droughts are likely to be accompanied by warmer temperatures, referred to here as global-change-type drought. Regional-scale tree die-off may become a major type of land surface change accompanying global warming that will need to be integrated into predictions of land surface–atmosphere interactions.
Session 1, Climate and Extreme Weather Events
Tuesday, 16 January 2007, 1:30 PM-5:30 PM, 214D
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