Early above- and belowground biomass fractionation, root diameter composition and allocation of cumulated fine root length per total leaf area of Populus clones have been measured for a pre-assessment of the risk for plantation establishment during spring drought conditions. Four clones of Populus × euramericana, and one P. nigra × P. maximowiczii clone (cv. Max 3), were planted in sandy mix substrate and were exposed to one normal and one deficit watering regime over 65-day greenhouse experiments conducted during early summer. The P. × euramericana hybrids showed plasticity of their root biomass fractions. Although clone Max 3 was among the productive clones, even under deficit watering, it was not able to respond plastically to deficit watering. It showed no increase in the root biomass fraction and no increase in the ratio of cumulated fine root length per total leaf area. Therefore, the clone Max 3 should not be planted under high risk for spring drought. Planting the investigated P. × euramericana clones under water deficit likely involves a lower risk, but clone differences within this group must be considered. It can be concluded that the water deficit response of biomass allocation to roots and of the ratio of fine root length per unit leaf area is suitable traits to improve drought risk assessments that are based on yield response of poplar clones to drought. Percent plant loss data and the yield at the end of the first SRC rotation will be suitable to verify the present greenhouse assessment.

已经测量了早期的地上和地下生物量分级，根直径组成以及胡杨无性系的每片叶总面积的累积细根长的分配，以便对春季干旱条件下建立人工林的风险进行预先评估。在沙质混合基质中种植了四个胡杨（Populus×euramericana）和欧洲黑杨（P. nigra × P. maximowiczii）克隆（cv。Max 3），并在早期的65天温室试验中，分别暴露于一种正常和一种亏水状态。夏天。该P.×欧美黑杂种表现出其根生物量部分的可塑性。尽管克隆Max 3属于高产克隆，即使在亏水情况下，它也无法对亏水进行塑性响应。它没有显示出根生物量分数的增加，并且累积的细根长度/总叶面积的比率没有增加。因此，克隆Max 3不应在春季干旱的高风险下种植。种植被调查的P.×euramericana缺水条件下的无性系可能具有较低的风险，但是必须考虑这一组内无性系的差异。可以得出结论，基于杨树无性系对干旱的产量响应，生物量分配对根的水分亏缺响应和每单位叶面积细根长度的比值是改善干旱风险评估的合适特征。在第一次SRC轮换结束时，植物损失百分比数据和单产将适合验证当前的温室评估。