For floodplain forests such as bottomland hardwood forests, large fluctuations in moisture availability can lead to stress from both flooded as well as drought conditions. Likewise, these forests can be diverse in species composition and the water use and drought strategies of co-occurring species will impact surrounding hydrology, nutrient dynamics and productivity. Therefore, the objectives of this study were to compare water use, canopy stomatal conductance and its response to environmental drivers in co-occurring bottomland hardwood species from four genera (Carya, Fraxinus, Quercus, Ulmus) during a drought and average rainfall year. Water use was similar across years in cherrybark oak and winged elm. For swamp chestnut oak, willow oak and shagbark hickory water use was about two thirds in the drought year compared with the average rainfall year and in American elm and green ash it was about one half. Species also varied in their responses of water use to VPD, reference canopy stomatal conductance values, and the timing of leaf senescence during the drought and average rainfall year which will impact ecosystem processes based on drought conditions and species composition. Shagbark hickory, winged elm and swamp chestnut oak exhibited the most declines in water use due to soil saturation. In general, species exhibited a tradeoff between flood tolerance and drought tolerance as well as between maximal water use potential and drought tolerance. In total, differences in water use and its response to environmental drivers during drought and non-drought years for bottomland hardwood forests will depend on species composition and these findings can benefit modeling efforts in temperate floodplain forests.

对于诸如平原硬木林之类的洪泛区森林，水分供应的巨大波动可能导致洪水和干旱条件下的压力。同样，这些森林的物种组成可能多种多样，同时存在的物种的用水和干旱策略将影响周围的水文，养分动态和生产力。因此，本研究的目的是比较干旱和平均降雨年中来自四个属（山核桃，水曲柳，栎属，乌尔姆斯）的共生底层硬木树种的水分利用，冠层气孔导度及其对环境驱动因素的响应。樱桃树橡树和有翼榆树的多年用水量相似。沼泽栗子橡木 与干旱年相比，干旱年份的柳树橡木和sha皮山核桃的用水量约为三分之二，美国榆树和绿灰的用水量约为二分之一。物种对VPD的用水响应，冠层气孔参考电导率值以及干旱和平均降雨年期间叶片衰老的时间也各不相同，这将根据干旱条件和物种组成影响生态系统过程。由于土壤饱和度，Shagbark山核桃，翅榆和沼泽板栗橡木的用水量下降最多。一般而言，物种表现出在耐水和耐旱之间以及最大水利用潜力和耐旱之间的权衡。总共，