ZHANG Guiling1,2, LI Yanqin3, LUO Xuqiang2,3,4, MO Chou3, REN yan3, LU Hanzhi3, QIN Huibin3
（1. School of Chemistry and Materials Science, Guizhou Education University, Guiyang 550018, China;
2. Karst Ecosystem Observation Research Station in Puding, Chinese Academy of Sciences, Puding Guizhou 562100, China;
3. School of Geography and Resources, Guizhou Education University, Guiyang 550018, China;
4. Guizhou Provincial Key Laboratory of Geographic State Monitoring of Watershed, Guiyang 550018, China）
Abstract: 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/mmol during the day time. The leaf WUE of all the eight plant species peaked at 9 AM. The lowest leaf WUE value was observed at 3 PM for three species of Millettia pachycarpa, Celtis sinensis and Coriaria nepalensis, and at 5 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 AM, 11 AM and 3 PM, while it was significant at 1 PM and 5 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.
Key words: karst secondary forest; common plants; seasonal drought; water use efficiency; variety characteristics
EARTH AND ENVIRONMENT Vol.49, No.1, Tot No.339, 2021, Page 25-31