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Interannual variation of evapotranspiration from forest and grassland ecosystems in western canada in relation to drought

机译:加拿大西部森林和草地生态系统蒸散量与干旱的年际变化

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Climate models predict rising temperatures and more frequent and prolonged droughts, particularly in the northern hemisphere and in the Canadian Prairies. However, few studies have examined the interannual variation in evapotranspiration (E) of northern terrestrial ecosystems in relation to drought. This study analyses multi-year (1998-2006), eddy-covariance measurements to quantify the seasonal and interannual variability in E from grassland and mature aspen, black spruce, and jack pine forest ecosystems in the dry interior plains of western Canada. It also investigates the response of E to the historic 2001-2003 drought in this region. Leaf area index (LAI) was a primary factor controlling the difference in E among different ecosystems in the same ecozone. Annual E was higher and more variable for the aspen forest (405 +/- 84 mm, mean +/- s.d.) and grassland (395 +/- 90 mm) than the black spruce (374 +/- 34 mm) and jack pine (300 +/- 20 mm) forests. Interannual variation of E was controlled by early spring soil temperature at all four sites, with warm springs enhancing annual E. Only the aspen forest and grassland showed a significant suppression of E by summer drought, related to reduced surface conductance at the aspen site, and to reduced surface conductance and early leaf senescence at the grassland. We conclude that the potential for drought impacts on annual E of northern ecosystems is greatest for grasslands, moderate for deciduous broadleaf aspen forests, and smallest for coniferous black spruce and jack pine forests. The forests of the Boreal Plains, adjacent to the prairie region, may ameliorate the onset of drought through the recycling of moisture to the atmosphere, whereas the prairie grasslands have only limited capacity to counteract drought through moisture recycling. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
机译:气候模型预测温度升高,干旱更加频繁和持续,特别是在北半球和加拿大大草原。但是,很少有研究研究与干旱有关的北方陆地生态系统蒸散量(E)的年际变化。这项研究分析了多年(1998-2006年)的涡度-协方差测量结果,以量化加拿大西部干燥的内陆平原草地和成熟的白杨,黑云杉和杰克松森林生态系统中E的季节性和年际变化。它还调查了E对该地区历史性2001-2003年干旱的响应。叶面积指数(LAI)是控制同一生态区中不同生态系统之间E差异的主要因素。白杨林(405 +/- 84毫米,平均+/-标准差)和草原(395 +/- 90毫米)的年E值高于黑云杉(374 +/- 34毫米)和杰克松树(300 +/- 20毫米)森林。在这四个地点,E的年际变化都受到早春土壤温度的控制,而温暖的泉水则提高了年度E。只有白杨林和草地由于夏季干旱而对E产生了显着的抑制作用,这与白杨处的地表电导降低有关,并且降低草地的表面电导和早期叶片衰老。我们得出的结论是,干旱对北部生态系统的年度E的影响最大的是草原,落叶阔叶白杨林适度,针叶黑云杉和杰克松林最小。毗邻草原地区的北方平原森林可以通过将水分循环到大气中来缓解干旱的发作,而草原草原通过水分循环来抵抗干旱的能力有限。官方版权(C)2010,Elsevier B.V.保留所有权利。

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