闽楠叶片功能性状及表型可塑性对其与杉木混交的响应

慢生（闽楠）与速生（杉木）树种混交后，植物是如何改变功能性状来适应环境，在资源获取与分配权衡中来实现共存？是人工林精准提质改造过程中的关键问题，研究了闽楠（Phoebe bournei）与杉木（Cunninghamia lanceolate）混交后，其叶厚（LT）、叶面积（LA）、比叶面积（SLA）、碳含量（LC）、氮含量（LN）、磷含量（LP）和氮磷比（N：P）7项性状指标的差异，探讨其各性状间的变异大小及其相关关系。结果表明：（1）与闽楠纯林相比，混交林闽楠叶片叶面积、比叶面积、叶碳含量、叶氮含量和氮磷比分别增加了16.78%、8.50%、3.12%、21.38%和17.61%，而叶厚与叶磷含量减少了8.80%和25.87%，除叶碳含量差异不显著，其他6项功能性状差异性均达到显著（P<0.05）。（2）混交使闽楠叶LC、LN、LP含量与LT、LA、SLA相关性均发生明显的变化，对其叶厚、叶面积、比叶面积及其交互作用对叶片C：N、C：P、N：P产生一定的影响，表明混交闽楠叶功能性状间的相关关系发生了适应性调整；（3）闽楠主要叶片功能性状的表型可塑性指数分布在0.04-0.33之间，叶厚、叶面积、比叶面积和氮磷比的可塑性变化不敏感（PPI<0.20），叶氮含量、磷含量的可塑性变化较敏感（PPI>0.20），其大小排序为LP > LN > N：P > LA > SLA > LT > LC。以上结果表明了闽楠杉木混交造林模式对闽楠叶形态性状可塑性变化影响较小，没有受到生长空间和光资源的限制，混交是一种较好的造林模式。但闽楠叶氮、磷含量可塑性变化在混交模式中十分敏感，表明生长过程中可能会受到N、P的限制，在培育过程中应注意N肥和P肥的及时补充。这一研究结果，将为今后速生树种与珍贵树种混交造林模式研究提供理论与数据支撑。

Response of Phoebe bournei leaf functional traits and phenotypic plasticity to its mixture with the Chinese fir

It is a key issue in the improvement of plantation quality that how slow-growing Phoebe bournei species change their functional traits to adapt to the environment and achieve coexistence in the trade-off of resource acquisition and distribution after mixed with fast-growing Chinese fir species. In this paper, we selected Phoebe bournei pure forest and Phoebe bournei-Chinese fir mixed forest with the same initial conditions and similar ages in the Jindong State-owned Forest Farm in Qiyang County, Yongzhou City, Hunan Province as the research objects. Samples were collected in different seasons to calculate the responses of the leaf functional traits to the mixed pattern, and compared the differences of Phoebe bournei leaf functional traits between the mixed forest and the pure forest. We mainly studied 7 traits including the leaf thickness (LT), leaf area (LA), specific leaf area (SLA), leaf carbon content (LC), leaf nitrogen content (LN), leaf phosphorus content (LP), and nitrogen-phosphorus ratio (N:P) of Phoebe bournei leaves in both Phoebe bournei pure forest and forest mixed with Cunninghamia lanceolata in Jindong National Forest Farm in Hunan Province, and also discussed the correlations and plasticity of these traits. The results indicated that (1) comparing with Phoebe bournei pure forest, LA, SLA, LC, LN, and N:P of Phoebe bournei leaves in mixed forest increased by 16.78%, 8.50%, 3.12%, 21.38%, and 17.61%, respectively, while the leaf thickness and phosphorus content reduced by 8.80% and 25.87%. All of the functional traits had significant differences (p<0.05) except the LC. (2) Phoebe bournei hybridization led to significant changes of the correlations between LC, LN, LP and LT, LA, SLA traits. There is also a certain impact on LT, LA, SLA and their interactions as well as leaf C:N, C:P, N:P, which means that the correlations between the Phoebe bournei leaf functional traits have been adjusted adaptively. (3) The phenotypic plasticity index of the main Phoebe bournei leaf functional traits was distributed between 0.04 and 0.33. LT, LA, SLA and N:P were not sensitive to plasticity changes (PPI<0.20), while leaf nitrogen and phosphorus contents were more sensitive to plasticity changes (PPI> 0.20). And the order was LP > LN > N:P > LA > SLA > LT > LC. The results above showed that the mixed mode had non-significant effect on the plasticity changes of Phoebe bournei leaf morphological traits, which was not limited by growth space and light resource. However, the plasticity changes of LN and LP were sensitive to mixing. In this case, the growth process may be restricted by N and P. As there is also an obvious interspecific competition in mixed forest, nitrogen and phosphate fertilizers should be applied during the cultivation process. This research result will provide theoretical and data support for the future research on mixed afforestation model of fast-growing and precious tree species.