不同混交比例对杉木和大叶榉幼苗功能性状的影响

了解林木功能性状在不同培育模式下的变异和关联，对揭示林木生态适应性及其生态功能具有重要意义。选取了亚热带地区两种常见人工林树种杉木、大叶榉幼苗为研究对象，设置4种不同栽培模式的盆栽试验：单一杉木（4C），单一大叶榉（4Z）和杉木、大榉树3种混栽模式（1C3Z、2C2Z、3C1Z），研究不同混交比例对其叶、茎、根功能性状的影响。结果表明：（1）杉木总叶面积、叶干物质含量、净光合速率、蒸腾速率和气孔导度在混栽模式下显著减小，而比叶面积显著增大；根长和比根长在不同处理间无显著差异；叶、茎、根生物量和单株总生物量在混栽模式下显著低于4C处理，不同混栽模式之间差异不显著。（2）大叶榉单叶面积在3C1Z处理下最高，总叶面积随大叶榉在树种组成中所占比例的降低而逐渐增大，比叶面积在不同处理间无显著差异，叶干物质含量、净光合速率、蒸腾速率和气孔导度均在2C2Z处理下最大，而瞬时水分利用效率在2C2Z处理下最小；根长在3C1Z处理下显著增大，比根长在不同处理间无显著差异；叶、茎、根生物量和单株总生物量随大叶榉在树种组成中所占比例的降低而逐渐增大。综合来看，杉木和大叶榉混合处理中杉木种间竞争大于种内竞争，而大叶榉相反；随杉木在混栽处理中比例减少，其主要通过增加比叶面积，提高净光合速率，减少茎生物量积累来适应种间竞争关系；而大叶榉随其在混栽处理中比例的减少，显著增加叶面积和根长来提高资源利用率，减少地下资源分配，提高地上茎生物量积累。因此，树种混交比例将显著影响林木功能性状及其生物量积累，选择适宜混交比例对混交林可持续经营具有重要意义。

Effects of mixing proportion on functional traits of Cunninghumia lanceolata and Zelkova schneideriana seedling

Understanding the variation and correlation of plant functional traits among different planting patterns is of great importance to reveal the ecological adaptability and function of different tree species. The variations of functional traits in two common tree species'' seedlings (Cunninghamia lanceolata and Zelkova schneideriana) in subtropical area were studied among different mixing proportions based on pot experiment. These mixing proportions included a single-species C. lanceolata planting pattern (4C), a single-species Z. schneideriana planting pattern (4Z) and three mixed treatments (1C3Z, 2C2Z, and 3C1Z). The results showed that:(1) total leaf area, leaf dry matter content, net photosynthetic rate, transpiration rate and stomatal conductance of C. lanceolata decreased significantly in the mixed treatments compared to 4C treatment, while specific leaf area increased significantly. Root length and specific root length were no difference among different treatments. Leaf biomass, stem biomass, root biomass and total biomass per plant of C. lanceolata among different treatments were significantly lower than in the 4C treatment, and these variables were no significant difference among mixed treatments. (2) mean leaf area of Z. schneideriana was the highest in the 3C1Z treatment. Total leaf area increased gradually with the decrease of the proportion of Z. schneideriana in tree species composition, specific leaf area was no significant difference among treatments, leaf dry matter content was the highest in the 2C2Z treatment. Net photosynthetic rate, transpiration rate and stomatal conductance of Z. schneideriana were the highest in the 2C2Z treatment, while the instantaneous water use efficiency was the lowest in the 2C2Z treatment. Root length of Z. schneideriana increased significantly in the 3C1Z treatment, while specific root length showed less variation among different treatments. Leaf biomass, stem biomass, root biomass and total biomass per plant of Z. schneideriana increased gradually with the decrease of the proportion of Z. schneideriana in tree species composition. Overall, interspecific competition was greater than intraspecific competition for C. lanceolata in mixed C. lanceolata and Z.schneideriana treatments, while the pattern was opposite for Z. schneideriana. With the decrease of the proportion of C. lanceolata in mixed treatments, C. lanceolata enhanced interspecific competition by increasing specific leaf area and net photosynthetic rate and reducing stem biomass accumulation. While with the decrease of the proportion of Z. schneideriana in mixed treatments, Z. schneideriana significantly increased leaf area and root length to improve resource utilization, and reduced underground resource allocation and increased aboveground stem biomass accumulation. Therefore, mixing proportion of tree species will significantly affect functional traits and biomass accumulation. Determining appropriate mixing proportion is of great significance for sustainable management of mixed-plantation.