Abstract Evapotranspiration (ET) typically accounts for 60–70% of precipitation in rural basins of the Southeastern United States. Since 1930, substantial reforestation of former croplands has occurred in the Piedmont and Appalachian Highlands in this area, leading to an expected increase in ET and reduction in baseflow. This study examines relationships between basin vegetative cover, abiotic factors, and water-budget partitioning in 45 USGS-gaged rural basins in the Southeastern US. Data are for the 1982–2014 water years with watersheds having ≥40% forest cover, crystalline-rock aquifers, minimal basin water export, and no large reservoirs. Long-term annual ET is calculated using the water-budget equation (ET = P-Q), which ranges from 641 to 971 mm/yr. (median 824). Vegetative cover and other basin variables are regressed against ET to quantify the effects of vegetative and forest types. Budyko analysis is employed to compare the watersheds and to evaluate factors affecting residuals. Regression analysis indicates that ET behavior is best explained by abiotic factors (i.e., precipitation and temperature) but forest-cover type also has some effect. Evergreen forest cover is less common than deciduous or mixed forest but has a positive relationship with ET, while deciduous and total forest have negative relationships with ET. Comparison of water-balance and Budyko-estimated ET indicates that deciduous and total forest are associated with negative residuals while evergreen is not significant. These results show that: forest cover effects on basin ET are complicated; forest-cover type is important for water-yield management in this region, and abiotic basin characteristics exert stronger control than forest cover on ET.

中文翻译：

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美国东南部农村流域森林类型、流域特征和流域ET之间的关系

摘要 蒸散量 (ET) 通常占美国东南部农村盆地降水量的 60-70%。自 1930 年以来，该地区的皮埃蒙特和阿巴拉契亚高地大量重新造林以前的农田，导致预计的 ET 增加和基流减少。本研究调查了美国东南部 45 个 USGS 计量的农村流域中流域植被覆盖、非生物因素和水预算分配之间的关系。数据来自 1982-2014 水年，流域森林覆盖率≥40%，结晶岩含水层，流域水出口最少，没有大型水库。使用水预算方程 (ET = PQ) 计算长期年度 ET，其范围为 641 至 971 毫米/年。（中位数 824）。植被覆盖度和其他盆地变量对 ET 进行回归，以量化植被和森林类型的影响。Budyko 分析用于比较流域并评估影响残差的因素。回归分析表明，ET 行为最好用非生物因素（即降水和温度）来解释，但森林覆盖类型也有一些影响。常绿林覆盖率低于落叶林或混交林，但与 ET 呈正相关，而落叶林和总林与 ET 呈负相关。水平衡和 Budyko 估计的 ET 的比较表明，落叶林和总林与负残差相关，而常绿林不显着。这些结果表明：森林覆盖对盆地ET的影响是复杂的；