The productivity of short‐rotation coppice (SRC) plantations with poplar (Populus spp.) strongly depends on soil water availability, which limits the future development of its cultivation, and makes the study of the transpirational water loss particularly timely under the ongoing climate change (more frequent drought and floods). This study assesses the transpiration at different scales (leaf, tree and stand) of four poplar genotypes belonging to different species and from a different genetic background grown under an SRC regime. Measurements were performed for an entire growing season during the third year of the third rotation in a commercial scale multigenotype SRC plantation in Flanders (Belgium). Measurements at leaf level were performed on specific days with a contrasted evaporative demand, temperature and incoming shortwave radiation and included stomatal conductance, stem and leaf water potential. Leaf transpiration and leaf hydraulic conductance were obtained from these measurements. To determine the transpiration at the tree level, single‐stem sap flow using the stem heat balance (SHB) method and daily stem diameter variations were measured during the entire growing season. Sap flow‐based canopy transpiration (E_c), seasonal dry biomass yield, and water use efficiency (WUE; g aboveground dry matter/kg water transpired) of the four poplar genotypes were also calculated. The genotypes had contrasting physiological responses to environmental drivers and to soil conditions. Sap flow was tightly linked to the phenological stage of the trees and to the environmental variables (photosynthetically active radiation and vapor pressure deficit). The total E_c for the 2016 growing season was of 334, 350, 483 and 618 mm for the four poplar genotypes, Bakan, Koster, Oudenberg and Grimminge, respectively. The differences in physiological traits and in transpiration of the four genotypes resulted in different responses of WUE.

中文翻译：

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短轮转生物能源培养第三次轮转期间小林杨蒸腾作用的基因型变化。

短轮伐期杨树（Populus spp.）林地的生产力强烈依赖于土壤水分的可用性，这限制了其栽培的未来发展，并且使得在持续的气候变化下蒸腾失水的研究显得尤为及时（更频繁的干旱和洪水）。本研究评估了在 SRC 制度下生长的四种杨树基因型在不同尺度（叶、树和林分）的蒸腾作用，这些基因型属于不同物种，具有不同的遗传背景。在佛兰德斯（比利时）商业规模的多基因型 SRC 种植园中，在第三次轮作的第三年对整个生长季进行了测量。在特定日期进行叶水平测量，对比蒸发需求、温度和传入的短波辐射，包括气孔导度、茎和叶水势。从这些测量中获得叶片蒸腾作用和叶片水力传导度。为了确定树木水平的蒸腾作用，使用茎热平衡（SHB）方法测量了单茎树液流量，并在整个生长季节测量了每日茎直径变化。还计算了四种杨树基因型的基于树液流的冠层蒸腾量（E c _{） 、季节性干生物量产量和水分利用效率（WUE；g地上干物质/kg蒸腾水）。}基因型对环境驱动因素和土壤条件具有截然不同的生理反应。树液流与树木的物候阶段和环境变量（光合有效辐射和蒸气压不足）密切相关。2016 年生长季四种杨树基因型 Bakan、Koster、Oudenberg 和 Grimminge 的总E _c分别为 334、350、483 和 618 mm。四种基因型的生理性状和蒸腾作用的差异导致了WUE的不同响应。