关键词: 沙柳, 光合速率, 日变化, 季节变化, 环境因子

Abstract: [Objective] The objective of this case was to understand the diurnal and seasonal dynamics of net photosynthetic rate of Salix psammophila,and to explore the main environmental factors that influence photosynthesis of Salix psammophila.[Method] Li-6400 portable photosynthesis system was used to measure photosynthetic parameters,environmental factors change of the shaliu;Soil temperature and humidity probe (TDT) was used to measure soil temperature and humidity.[Results] The result indicated that:① The diurnal dynamics and peak time of Salix psammophila were influenced by environmental factor.Diurnal changes of the net photosynthetic rate (P_n) were one-peak curve that is at 8:30-10:30.Seasonal change of net photosynthesis rate was in sequence of late August to middle September > late June to early July > middle July to middle August;② Diurnal changes of transpiration rate (T_r) were also one-peak curve.The peak was detected between 10:30-14:30,which belongs to ecological type of a "non-transpiration middle depression" because no significant peak was found;③ The direct path coefficient of environmental factors was in sequence of VWC_soil > RH > T_soil > P_ar > T_air > CO₂;the sum of indirect path coefficient was in sequence of T_soil > T_air > VWC_soil> RH > CO₂ > P_ar,VWC_soil,RH are the main limiting factors that influence the photosynthetic of Salix psammophila.[Conclusion] Diurnal changes of net photosynthetic rates of Salix psammophila could be interpreted as one-peak curves.But when it is under bad environmental conditions,such as intensive solar,high temperature,drought and other harsh environments,the type of diurnal dynamics may change while peak time may happen early.Moisture is the major environmental factor influencing net photosynthetic rate of Salix psammophila.

Key words: Salix psammophila, photosynthetic rate, diurnal changes, seasonal changes, environmental factors