The bioeconomy strategies in the EU are expected to lead to increased consumption of woody biomass. The empirical knowledge of asexually regenerated hybrid aspen (Populus tremula L. × P. tremuloides Michx.) coppice stand production and responses to silvicultural treatments is still poor. In hemiboreal Estonia, four different management treatments (corridor thinning with ~67% removal, cross-corridor thinning with ~89% removal, single-tree thinning with ~97% removal and control with no management activity) were applied in a 2-year-old hybrid aspen coppice stand, and effects on tree above-ground biomass and leaf characteristics were investigated during three post-thinning years. Hybrid aspen mean annual increment of above-ground biomass peaked at 6.3 (range: 3.6–8.5) Mg ha⁻¹ in year 4, suggesting 4–5 years as an optimal age for bioenergy harvest. The above-ground growth characteristics of dominant trees did not differ from control area. The current annual increment of the height, biomass and leaf growth efficiency (LGE) of dominant trees under single-tree thinning remained even lower compared with the other treatments. Dominant trees were more efficient in resource use, as their LGE values were 21–50% higher compared with the stand average value. Poor growth, high mortality and low LGE in single-tree thinning indicate that the low density of remaining trees created an imbalance between leaf area and parent root system. The hybrid aspen coppice stand showed a high biomass production during early development. We recommend modest early thinning in vegetative hybrid aspen stands to ensure a sufficient balance between leaf area and parent root system.

中文翻译：

---

早期间伐处理对杂交白杨矮林地上生长，生物量产生，叶面积指数和叶片生长效率的影响

欧盟的生物经济战略有望导致木质生物量的消费增加。无性繁殖的杂交白杨（Populus tremula L.× P. tremuloides Michx。）矮林林产量和对造林处理的反应的经验知识仍然很薄。在半波状爱沙尼亚，在2年内应用了四种不同的处理方法（去除约67％的走廊间苗，去除约89％的跨走廊间苗，去除约97％的单树间苗和无管理活动的对照）。在稀疏后的三年中研究了古老的杂种杨木小灌木林林分，以及对树地上生物量和叶片特性的影响。杂种白杨地上生物量的年平均增加量峰值为6.3（范围：3.6–8.5）Mg ha ^-1在第4年，建议4-5岁为生物能源收获的最佳年龄。优势树的地上生长特性与对照区没有差异。与其他处理相比，目前单株间伐后优势树的株高，生物量和叶片生长效率（LGE）的年增幅甚至更低。优势树的资源利用效率更高，因为它们的LGE值比林分平均值高21–50％。单棵树间伐的生长不良，高死亡率和低LGE表示剩余树木的低密度造成了叶面积和亲本根系之间的不平衡。混合白杨小灌木林林分在早期发育过程中显示出高生物量产量。