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| DOI：10.13522/j.cnki.ggps.2019472 |
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| The Response of Sap Flow in Young Acacia Mangium to Environmental Changes During Rainy Season in Hainan |
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NIU Yongqiang, WU Zheying, XU Wenxian, HAN Qi, ZHAO Congju
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1. Danzhou Forest Farm, Danzhou 571749, China; 2. School of Life Sciences, Hainan Normal University, Haikou 571158, China; 3. School of Geography and Environment Science, Hainan Normal University, Haikou 571158, China
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| Abstract: |
| 【Objective】Sap flow in plant is modulated by many biotic and abiotic factors, and the objective of this paper is to study how sap flow in young Acacia mangium responds to environmental changes during rainy season in Hainan province of south China. 【Method】The experiment was conducted at Danzhou forest farm in western Hainan; sap flow in young Acacia mangium and changes in its immediate surrounding environment were measured continuously using the Dynagage sap flow sensor and DL2e environmental data acquisition systems, respectively, from June to October in 2014. The relationship between the sap flow and the environmental factors was analyzed using different methods. 【Result】In sunny or cloudy days, the sap flow showed diurnal variation, increasing to a peak followed by a oscillating decline, with a daily average of 3.07 mL/(cm2·h) and 1.59 mL/(cm2·h) respectively. In contrast, the sap flow in rainy days varied gently with a daily average of 0.78 mL/(cm2·h). The sap flow peaked at 09:00 in the morning on sunny days characterized by a noticeable transpiration plateau, while cloudy or rainy days delayed the arrival of the sap-flow peak and blurred the transpiration plateau. Path analysis showed that in sunny days the change in sap flow was affected mainly by water vapor pressure deficit (VPD), air relative humidity (RH) and air temperature (Ta), while in cloudy days it was affected by Ta, VPD and photosynthetically active radiation (PAR) more. On rainy days, PAR and Ta impacted on the sap flow most.【Conclusion】The sap flow in young Acacia mangium shows diurnal variation, and it peaks ahead of PAR. The stronger the PAR is, the earlier the sap flow peaks. On sunny, cloudy or rainy days, the dominant factor affecting the sap flow is VPD, Ta, and PAR, respectively. |
| Key words: dynagage sap flow sensors; Acacia mangium; sap flow velocity; environmental factors |
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