The regression tree method is used to upscale evapotranspiration (ET) measurements at eddy-covariance (EC) towers to the grassland ecosystems over the Dryland East Asia (DEA). The regression tree model was driven by satellite and meteorology datasets, and explained 82% and 76% of the variations of ET observations in the calibration and validation datasets, respectively. The annual ET estimates ranged from 222.6 to 269.1 mm yr−1 over the DEA region with an average of 245.8 mm yr−1 from 1982 through 2009. Ecosystem ET showed decreased trends over 61% of the DEA region during this period, especially in most regions of Mongolia and eastern Inner Mongolia due to decreased precipitation. The increased ET occurred primarily in the western and southern DEA region. Over the entire study area, water balance (the difference between precipitation and ecosystem ET) decreased substantially during the summer and growing season. Precipitation reduction was an important cause for the severe water deficits. The drying trend occurring in the grassland ecosystems of the DEA region can exert profound impacts on a variety of terrestrial ecosystem processes and functions.
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机译:回归树方法用于对旱地东亚(DEA)上的草地生态系统的涡度-协方差(EC)塔进行高级蒸散(ET)测量。回归树模型由卫星和气象数据集驱动,分别解释了校准和验证数据集中ET观测值的82%和76%。从1982年到2009年,DEA地区的年度ET估计值范围从222.6到269.1 mm yr -1 sup>,平均为245.8 mm yr -1 sup>。生态系统ET呈下降趋势在此期间,DEA区域超过61%,尤其是在蒙古和内蒙古东部的大多数地区,这是由于降水减少所致。 ET增加主要发生在西部和南部DEA地区。在整个研究区域,夏季和生长季节的水平衡(降水量与生态系统ET之间的差异)大大降低。减少降水是造成严重缺水的重要原因。 DEA地区草地生态系统中发生的干旱趋势可能对各种陆地生态系统过程和功能产生深远影响。
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