沙柳光合速率动态变化及其主要环境因子

【目的】了解沙柳(Salix psammophila)净光合速率(Pn)的日动态和生长季节动态规律,探索影响其光合作用的主要环境因子。【方法】使用Li-6400便携式光合测定系统,测定沙柳叶片光合参数及环境因子变化;使用土壤温湿度探头(TDT)测定土壤温湿度。【结果】①沙柳净光合速率日变化类型及峰值出现时间受环境因素影响。试验中表现为单峰型,峰值出现在8:30-10:30;净光合速率季节变化表现为:8月下旬-9月中旬>6月下旬-7月上旬>7月中旬-8月中旬;②蒸腾速率(Tr)日变化为单峰曲线,在10:30-14:30之间出现峰值,但峰值不明显,属"非蒸腾午休型"的水分生态类型;③环境影响因子直接通径系数大小为:VWCsoil>RH>Tsoil>Par>Tair>CO2,间接通径系数之和大小为:Tsoil>Tair>VWCsoil>RH>CO2>Par,VWCsoil、RH是影响其光合作用的主要因子。【结论】沙柳净光合日变化为单峰曲线,在高光强、高温、干旱等恶劣环境下沙柳日变化类型会发生变化,峰值会提前。水分是沙柳光合作用的主要环境影响因子。

Photosynthetic Dynamics and to the Relevant Environmental Factors of Salix psammophila

【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(Pn) 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(Tr) 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 VWCsoil > RH > Tsoil > Par > Tair > CO2;the sum of indirect path coefficient was in sequence of Tsoil > Tair > VWCsoil> RH > CO2 > Par,VWCsoil,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.