Journal Article

Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought

Troch, Peter A, Grupo de Ingeniería y Gestión Ambiental (GIGA), Breshears, David D, Huxman, Travis E, Barron Gafford, Greg A, Zou, Chris B, Guardiola Claramonte, Maite, Villegas Palacio, Juan Camilo

2009

Overview

Large-scale biogeographical shifts in vegetation are predicted in response to the altered precipitation and temperature regimes associated with global climate change. Vegetation shifts have profound ecological impacts and are an important climate-ecosystem feedback through their alteration of carbon, water, and energy exchanges of the land surface. Of particular concern is the potential for warmer temperatures to compound the effects of increasingly severe droughts by triggering widespread vegetation shifts via woody plant mortality. The sensitivity of tree mortality to temperature is dependent on which of 2 non-mutually-exclusive mechanisms predominates—temperature-sensitive carbon starvation in response to a period of protracted water stress or temperature-insensitive sudden hydraulic failure under extreme water stress (cavitation). Here we show that experimentally induced warmer temperatures ( 4 °C) shortened the time to droughtinduced mortality in Pinus edulis (pin˜ on shortened pine) trees by nearly a third, with temperature-dependent differences in cumulative respiration costs implicating carbon starvation as the primary mechanism of mortality. Extrapolating this temperature effect to the historic frequency of water deficit in the southwestern United States predicts a 5-fold increase in the frequency of regional-scale tree die-off events for this species due to temperature alone. Projected increases in drought frequency due to changes in precipitation and increases in stress from biotic agents (e.g., bark beetles) would further exacerbate mortality. Our results demonstrate the mechanism by which warmer temperatures have exacerbated recent regional die-off events and background mortality rates. Because of pervasive projected increases in temperature, our results portend widespread increases in the extent and frequency of vegetation die-off.

• Publisher: National Academy of Sciences,Estados Unidos,National Acad Sciences
• Subject: air temperature / Bark / Biogeography / Biological Sciences / Carbon / Carbon - metabolism / Cavitation / Climate change / Die off / Drought / Droughts / environmental impact / forest decline / Forest ecosystems / forest trees / Global climate / Global climate models / global warming / Mortality / Pinus - growth & development / Pinus - metabolism / Pinus edulis / Plant Leaves - metabolism / Respiration / Scolytidae / Sensitivity and Specificity / Temperature / Temperature effects / Time Factors / tree mortality / Trees / Trees - growth & development / Trees - metabolism / Vegetation / Water deficit / Water stress / Water temperature / Woody plants