A 7-year study was conducted to examine the growth (diameter and root) response of Norway spruce (Picea abies (L.) Karst.) seedlings to elevated CO₂ (CO_2ELV, 770 μmol (CO₂) mol⁻¹) in different mixture types (monospecific (M): a Norway spruce seedling surrounded by six spruce seedlings, group-admixture (G): a spruce seedling surrounded by three spruce and three European beech seedlings, single-admixture (S): a spruce seedling surrounded by six beech seedlings). After seven years of treatments, no significant effect from elevated CO₂ was found on the root dry mass (p = 0.90) and radial growth (p = 0.98) of Norway spruce. Neither did we find a significant interaction between [CO₂] × mixing treatments (p = 0.56), i.e. there was not a significant effect of CO₂ concentrations [CO₂] in all the admixture types. On the contrary, spruce responses to admixture treatments were significant under CO_2AMB (p = 0.05), which demonstrated that spruce mainly increased its growth (diameter and root) in M and neighbouring with beech was not favourable for spruce seedlings. In particular, spruce growth diminished when growing beside high proportions/numbers of European beech (S). Here, we also evaluated the association between tree-ring formation and climatic variables (precipitation and air temperature) in different admixture types under elevated and ambient CO₂ (CO_2AMB, 385 μmol (CO₂) mol⁻¹). Overall, our result suggests that spruce responses to climate factors can be affected by tree species mixing and CO₂ concentrations, i.e. the interaction between climatic variables × admixture types × [CO₂] could alter the response of spruce to climatic variables.

进行了一项为期 7 年的研究，以检查挪威云杉 ( Picea abies (L.) Karst.) 幼苗对升高的 CO ₂ (CO _2ELV , 770 μmol (CO ₂ ) mol ^-1 )的生长（直径和根）响应不同的混合物类型（单种（M）：挪威云杉幼苗被六棵云杉幼苗包围，组混合物（G）：云杉幼苗被三棵云杉和三棵欧洲山毛榉幼苗包围，单一混合物（S）：云杉幼苗被包围由六棵山毛榉幼苗）。经过 7 年的处理，未发现CO ₂升高对根干质量 ( p  = 0.90) 和径向生长 ( p = 0.98) 的挪威云杉。我们也没有发现 [CO ₂ ] × 混合处理之间的显着相互作用（p  = 0.56），即在所有混合物类型中 CO ₂浓度 [CO ₂ ]没有显着影响。相反，在 CO _2AMB ( p = 0.05），这表明云杉主要增加了其在 M 中的生长（直径和根），而与山毛榉相邻的则不利于云杉幼苗。特别是，当与高比例/数量的欧洲山毛榉 (S) 一起生长时，云杉的生长会减弱。在这里，我们还评估了在升高和环境 CO ₂ (CO _2AMB , 385 μmol (CO ₂ ) mol ^-1 )下不同混合物类型中树木年轮形成与气候变量（降水和气温）之间的关联。总体而言，我们的结果表明，云杉对气候因素的响应会受到树种混合和 CO ₂浓度的影响，即气候变量之间的相互作用 × 混合物类型 × [CO ₂] 可以改变云杉对气候变量的响应。