Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought
Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought
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DOI：
10.1073/pnas.0901438106
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发表时间：
2009-04-28
影响因子：
11.1
通讯作者：
Huxman, Travis E.
中科院分区：
文献类型：
--
作者：
Adams, Henry D.;Guardiola-Claramonte, Maite;Huxman, Travis E.
大规模的植被地理变化的预测，以响应与全球气候变化相关的降水和温度制度的改变。植被变化通过改变地表的碳、水和能量交换，产生深刻的生态影响，是重要的气候-生态系统反馈。特别令人关切的是，气温升高可能会加剧日益严重的干旱的影响，通过木本植物死亡引发广泛的植被变化。树木死亡率对温度的敏感性取决于2种非互斥机制中的哪一种占主导地位--温度敏感的碳饥饿，以响应一段时间的长期水分胁迫或温度不敏感的极端水分胁迫下的突然水力故障（空化）。在这里，我们表明，实验诱导的温暖的温度（约4摄氏度）缩短了近三分之一的时间，干旱诱导的死亡率在紫松树（松树缩短松树）树木，与温度相关的差异，在累积呼吸成本牵连碳饥饿的主要机制死亡。将这种温度效应外推到美国西南部缺水的历史频率，预测仅由于温度，该物种的区域规模树木死亡事件的频率增加了5倍。由于降水量的变化和生物因子造成的压力的增加，预计干旱频率将增加。例如，在一个实施例中，树皮甲虫）将进一步加剧死亡率。我们的研究结果表明，变暖的温度加剧了最近的区域死亡事件和背景死亡率的机制。由于普遍预计温度升高，我们的结果预示着植被死亡的范围和频率普遍增加。
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 (approximate to 4 degrees C) shortened the time to drought-induced mortality in Pinus edulis (pinon 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.