木兰科常绿与落叶物种叶片构建策略的差异

Different Leaf Construction Strategies in Evergreen and Deciduous Species of Magnoliaceae

摘要:

为探究木兰科（Magnoliaceae）常绿与落叶物种叶片构建的生理生态策略，选取黄山木兰（Yulania cylindrica）、玉兰（Y. denudata）和鸡公山玉兰（Y. jigongshanensis）3种落叶物种，以及荷花玉兰（Magnolia grandiflora）、含笑花（Michelia figo）、石碌含笑（M. shiluensis）3种常绿物种，对其叶片构建成本和叶片寿命相关的性状进行比较。结果表明，木兰科3落叶种的单位叶片面积成本（CC_area）显著低于3常绿种，但落叶和常绿物种的叶片质量成本（CC_mass）差异不显著。落叶物种的叶氮、磷含量（N_mass，P_mass）和比叶面积（SLA）均显著高于常绿物种，而叶片寿命（LLS）显著低于常绿物种。CC_area与LLS呈显著正相关，N_mass、P_mass和SLA均与LLS呈显著负相关。这说明木兰科玉兰属落叶物种单位面积叶片构建成本小于常绿物种；落叶物种叶片寿命短，但采取低成本构建策略，提高比叶面积获得更多光资源，增加营养积累，也揭示了玉兰属落叶物种适应北亚热带较短的生长季和较低水热条件的生理生态策略。

Abstract:

In order to reveal the ecophysiological strategies of leaf construction in Magnoliaceae evergreen and deciduous species, the characters related with leaf lifespan and leaf construction cost of six Magnoliaceae species, including three deciduous species, Yulania cylindrical, Y. denudate and Y. jigongshanensis, and three evergreen species, Magnolia grandiflora, Michelia figo and M. shiluensis were compared. The results showed that construction cost per leaf area (CC_area) of deciduous species was significantly lower than that of evergreen species, but their construction cost per leaf dry mass (CC_mass) was similar. Nitrogen and phosphorous concentration (N_mass, P_mass) in leaves of deciduous species were significantly higher than that of evergreen species. Evergreen species had significantly low specific leaf area (SLA) but long leaf lifespan (LLS). There were a negative correlation between CC_area and LLS, whereas other three traits (SLA, N_mass and P_mass) had a positive correlation with LLS. In conclusion, deciduous species adopted the low-cost strategy, with short leaf lifespan and high SLA to obtain more light source and nutrition storage compared to evergreen species. It was revealed the ecophysiological strategy of deciduous species of Magnoliaceae to adapt short growth season and low hydrothermal condition in north subtropics.