柯-青冈常绿阔叶林优势树种叶片性状变异及适应策略

厘清叶片功能性状的变异及性状间的权衡关系,对揭示植物对环境变化的响应及适应策略具有重要意义。以中亚热带柯(Lithocarpus glaber)-青冈(Cyclobalanopsis glauca)常绿阔叶林为对象,测量了1 hm²固定监测样地内6个优势树种的叶面积(LA)、比叶面积(SLA)、干物质含量(LDMC)、叶片厚度(LT)、叶片碳(LC)、叶片氮(LN)、叶片磷(LP)含量和叶片碳氮比(LC ∶ LN)8个功能性状,采用多重比较、主成分分析(PCA)法分析了群落叶片功能性状的生活型、种内和种间变异及性状间关系。结果表明：(1)群落内叶片功能性状种内、种间差异显著,变异中等(CV： 0.02-0.59),其结构性状的可塑性较化学性状保守,变异格局符合"性状空间变异分割假说";针叶树种的LA、SLA显著低于阔叶树种,常绿树种的LC和LDMC最小,而落叶树种的SLA、LN和LP最大以及LT和LC ∶ LN最小。(2)群落叶片功能性状变异主要来源于生活型和种间变异,种内变异亦有显著贡献;生活型对多数性状的贡献率较大,其对LDMC、LC ∶ LN的贡献分别高达93.11%和91.76%;种间变异(LDMC除外)对结构性状的贡献率均高于化学性状;种内变异对LP的贡献率(23.66%)较种间变异高。(3)叶片性状之间多表现出显著相关关系,针叶树和阔叶树在PCA排序图中聚集于不同区域,叶经济型谱在柯-青冈群落中具有适用性。不同树种通过叶片结构、化学性状之间的权衡策略来适应环境变化,从而实现群落物种共存。结果可为理解森林群落物种的环境适应策略、预测群落动态变化和制定植被恢复措施提供科学依据。

Variation in leaf functional traits and adaptation strategies of dominant tree species in a Lithocarpus glaber-Cyclobalanopsis glauca evergreen broad-leaved forest

Elucidating the variation in leaf functional traits and the trade-off relationships among those traits are of great significances to reveal the response mechanism''s and adaptation strategies of plants towards changing environment. The variation of plant functional traits organically links the species adaptation strategy with the ecosystem functions and processes, and the ranges including interspecific and intraspecific variations vary with species and are closely related to environmental gradients. Meanwhile, the leaf economics spectrum (LES) at the global scale can reflects the trade-off relationships between the main structural, chemical and physiological traits. However, local community puts environmental factors and functional traits in the same system, and the main reasons responsible for the variation in functional traits and the applicability of LES still need to be deeply investigated. In this study, we collected 8 leaf functional traits of 6 dominant tree species in a 1 ha permanent monitoring plot of a Lithocarpus glaber-Cyclobalanopsis glauca subtropical evergreen broad-leaved forest, and the studied traits included leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT), leaf carbon (LC), leaf nitrogen (LN), leaf phosphorus (LP) content and carbon-nitrogen ratio (LC :LN). We used multiple comparison and principal component analysis (PCA) to explore the variation in leaf functional traits at the interspecific, intraspecific and life form levels, and to analyze the relationship among those functional traits. The results showed that:(1) Leaf functional traits were significantly different at the intraspecific and interspecific levels in this community. There was a moderate variation with a coefficient variation (CV) ranging from 0.02 to 0.59, and the structural traits were more conservative than chemical traits. The variation pattern of leaf functional traits conformed to "a spatial trait variance partitioning hypothesis". Leaf functional traits significantly differed among life forms, with lower SLA and LA for coniferous tree species compared to those for broad-leaved tree species, lowest LC and LDMC for evergreen trees, yet the deciduous tree species exhibited the highest SLA, LN and LP along with the lowest LT and LC :LN. (2) Life form and interspecific differences contributed the most to the variation in leaf functional traits, and intraspecific differences also contribute significantly to those variations with lower contribution rate. Life forms had relative higher contribution to the variation in most functional traits with the contribution rate reaching 93.11% and 91.76% for LDMC and LC:LN, respectively. The contribution rate of interspecific variation (except LDMC) to structural traits was higher than that to chemical traits. Intraspecific variation had a higher contribution rate to LP (23.66%) than interspecific variation. (3) There was a significant correlation between leaf functional traits. Conifers and broad-leaved trees clustered in different areas of PCA ordination chart. The leaf economics spectrum was applicable in the subtropical evergreen broad-leaved forest, and diverse tree species could coexist in this community by the trade-off strategies among leaf structural and chemical traits. The results could provide a scientific basis for understanding the adaptation strategies of diverse tree species to environment, predicting the dynamic changes of community and formulating vegetation restoration strategy.