季节性干旱下喀斯特次生林不同树种水分利用效率变化

Change of Water Use Efficiency of Different Species in Karst Secondary Forest under Seasonal Drought

植物叶片水分利用效率(WUE)对环境变化的响应特征和机制是理解生态系统碳循环和水循环及其耦合关系的基础。为探讨季节性干旱下喀斯特次生林中不同植物的WUE变化,以普定次生林通量观测站内的喀斯特次生林为例,在连续干旱背景下分别对8种常见植物的叶片WUE进行了测定分析。结果表明:(1)研究区常见植物的叶片WUE日间主要在0.65~7.73μmol/mmol之间变化。8种植物的叶片WUE均以上午9点最大,厚果崖豆藤(Millettia pachycarpa)、朴树(Celtis sinensis)和马桑(Coriaria nepalensis)的WUE均在下午3点就降到最低,而铁线莲(Clematis florida)、木通(Akebia quinata)、石岩枫(Mallotus repandus)、梓树(Catalpa ovata)和构树(Broussonetia papyrifera)的WUE则在下午5点才降到最低。厚果崖豆藤、铁线莲、石岩枫、朴树、构树的WUE日间变化均较显著。(2)研究区植物叶片的WUE以藤本植物最高。上午9点、11点和下午3点,植物叶片WUE的种间差异均不显著,而在下午1点、5点,植物叶片WUE在种间均存在显著差异。(3)石岩枫和木通的叶片WUE与环境光照强度均呈显著正相关关系。朴树和铁线莲的叶片WUE与环境相对湿度均呈极显著正相关关系。厚果崖豆藤的叶片WUE与环境空气温度间也呈现出极显著的正相关关系。朴树、构树、马桑、石岩枫、铁线莲、厚果崖豆藤的叶片WUE与净光合速率均显著正相关,木通的叶片WUE与蒸腾速率显著负相关。研究区8种植物叶片WUE与叶面水汽压亏缺间的相关性均不显著。(4)植物种和外部环境对研究区植物叶片的WUE均有显著影响,木通、厚果崖豆藤、铁线莲在遭遇连续干旱后叶片WUE均较高,对生境恶劣的喀斯特环境具有较强的适应能力。

The response characteristics and mechanisms of water use efficiency( WUE) of plant leaves under the environmental changes are the basis for understanding the carbon and water cycles in the ecosystem and their coupling relationships.In order to investigate the leaf WUE changes of different plants under seasonal drought in the karst secondary forest,the Puding karst secondary forest flux observation station was taken as an example with the leaf WUE of eight common plants been measured and analyzed under the background of continuous drought.The results showed that:( 1) The leaf WUE of the common plant in the study area varied from 0.65 to 7.73 μmol/mmolduring the day time.The leaf WUE of all the eight plant species peaked at 9: 00 AM.The lowest leaf WUE value was observed at 3: 00 PM for three species of Millettia pachycarpa, Celtis sinensis and Coriaria nepalensis, and at 5: 00 PM for Clematis florida, Akebia quinata, Mallotus repandus, Catalpa ovata, and Broussonetia papyrifera.The diurnal variation of leaf WUE of five plant species, including M.pachycarpa, C.florida, M.repandus, C.sinensis, and B.papyrifera, was significant.( 2) The leaves of liana had the highest WUE in the study area.The difference of leaf WUE between species was not significant at 9: 00 AM, 11: 00 AM and3: 00 PM, while it was significant at 1: 00 PM and 5: 00 PM.( 3) The leaf WUE of M.repandus and A.quinata showed a significant positive correlation with the illumination intensity.The leaf WUE of C.sinensis and C.florida showed a significant positive correlation with the environmental relative humidity.The leaf WUE of M.pachycarpa exhibited a significant positive correlation with the air temperature.The leaf WUE of C.sinensis, B.papyrifera, C.nepalensis, M.repandus, and M.pachycarpa demonstrated significant positive correlations with the net photosynthetic rate,while the leaf WUE of C.sinensis and the transpiration rate was significantly negative correlated.The correlation between leaf WUE and vapor pressure deficit at the leaf surface was not significant for all eight plant species in the study area.( 4) Plant species and external environment have significant effects on the leaf WUE in the study area.A.quinata, M.pachycarpa, and C.florida had high leaf WUE after continuous drought, indicating they have strong adaptabilities to the harsh environment in karst area.