Short rotation coppices play an important role in providing biomass for energetic use. Mixing fast-growing tree species in short rotation coppices may show complementarity effects and increased yield. The aim of this study was to analyze the effect of species interaction in mixed short rotation coppices with fast-growing Populus spp.-hybrids and the N-fixing Robinia pseudoacacia. Four different Populus-hybrids (AF2, Fritzi Pauley, Hybride 275 and Max 1), planted alternately in pure and mixed stands with R. pseudoacacia were used for the analysis. Height and root collar diameter were measured once a year, over a period of four years (2014–2017). Additionally, in the third year, aboveground competition was surveyed with a terrestrial laser scanner and root biomass was analyzed to assess belowground competition. Soil nitrogen was also determined in order to verify enrichment properties of mixtures compared to pure stands. Populus-hybrids’ stem volume showed no significant differences between stand types in the first year after planting. In the second and third year, however, two Populus-hybrids (AF2 and Max 1) had a higher stem volume increment of up to 3.8 times than stem volume increment in pure stands. This may be related to the fact that soil nitrogen was 39% higher in the mixtures than in pure stands. However, in the 4th year after stand establishment, R. pseudoacacia’s crowns were so massive and broad, that this species was far more competitive than the Populus-hybrids. With the exception of P. ‘Fritzi Pauley’, which showed no significant differences between stand types, growth rates reversed for the other three Populus-hybrids. AF2, Max 1 and Hybride 275 showed up to 75% lower stem volume increment in mixtures compared to pure stands. We assume that, in spite of the initially observed facilitation between the species, the competition exerted by R. pseudoacacia started dominating after 4 years and began to surpass the benefits of facilitation.

短周期旋转coppepices在提供高能生物质方面起着重要作用。将快速生长的树种混入短轮作中可能显示出互补效应并增加了产量。这项研究的目的是分析物种混合在具有快速增长的胡杨（Populus spp.-hybrids）和固氮刺槐（Robinia pseudoacacia）的混合短轮作中的相互作用。四个不同的胡杨-hybrids（AF2，Fritzi波利，杂合275和Max 1），为纯的和混合的看台与交替种植刺槐被用于分析。在四年（2014-2017）期间，每年测量一次身高和牙根直径。此外，在第三年，使用地面激光扫描仪对地上竞争进行了调查，并对根生物量进行了分析以评估地下竞争。还确定了土壤氮，以验证与纯林相比混合物的富集特性。种植后第一年，胡杨的茎干体积在林分类型之间没有显着差异。但是在第二年和第三年，有两个胡杨杂交种（AF2和Max 1）的茎体积增量比纯林中的茎体积增量高3.8倍。这可能与以下事实有关：混合物中的土壤氮含量比纯林分高39％。但是，在林分建立后的第4年，假阿拉伯树冠的冠是如此之大和宽阔，以至于该物种比胡杨杂种更具竞争性。除了P. “ Fritzi Pauley”（林分类型没有显着差异）外，其他三个杨树的生长速度都相反-杂种。与纯林相比，AF2，Max 1和Hybride 275在混合物中的茎体积增量最多降低了75％。我们假设，尽管最初观察到了物种之间的促进作用，但假想叶罗非鱼所施加的竞争在4年后开始占主导地位，并开始超越促进作用。