基于离体测量估计长白落叶松原位最大净光合速率的方法

Estimating in situ maximum net photosynthetic rate of Larix olgensis based on abscised measurement

以黑龙江省帽儿山林场15年生长白落叶松人工林为研究对象,通过对针叶进行原位及离体测量获取其原位最大净光合速率(SP_(n max))及离体最大净光合速率(AP_(n max)),分析AP_(n max)随离体时间(t_a)的变化规律,建立SP_(n max)与AP_(n max)和t_a的函数关系,并分析了林木大小及环境因子对AP_(n max)下降过程的影响,构建了长白落叶松SP_(n max)预估模型.结果表明:在不恢复水分供应的条件下,针叶AP_(n max)随t_a的增加而降低,且水汽压亏缺(VPD)和叶片温度(T_(leaf))越高,AP_(n max)的下降速度越快、幅度越大.以VPD和t_a为自变量的线性预估模型对SP_(n max)的拟合效果最好(Ra^2为0.774,RMSE为20.73),模型的预估精度随着t_a的增加而降低,t_a超过20min后,模型预估精度稳定在97%左右.本文采用离体测量方法通过建立回归模型估计长白落叶松的SP_(n max),不仅具有较好的预估能力和相对稳定的估计精度,同时大大提高了SP_(n max)的测定效率,具有较高的应用价值.

The data of needle in situ maximum net photosynthetic rate（ SP（n max）） and abscised maximum net photosynthetic rate（ AP（n max）） were measured for the 15 year-old planted Larix olgensis stand in the Maoershan Forest Farm,Heilongjiang Province,China. The change pattern between AP（n max）and abscised time（ ta） was analyzed and the functional relationship between SP（n max）and AP（n max）with ta was also established. Finally,the prediction model of SP（n max）for planted L. olgensis trees was developed by analyzing the effect of tree size and environmental factors on the decline of AP（n max）. The results showed that needle AP（n max）decreased with the increase of ta without restoring water supply. The higher vapor pressure deficit（ VPD） and the leaf temperature（ T（leaf）） would lead to faster and lager reduction of AP（n max）. Taking VPD and ta as the independent variables of the linear regression model had the best goodness-of-fit for SP（n max）（ Ra^2 were 0. 774 and RMSE was 20. 73）.The model prediction precision decreased with the increase of ta,but after 20 min it would be stabilized at 97%. Overall,estimating SP（n max）of L. olgensis trees by developing regression model based on abscised measurement not only had a well predictive ability but also had a stable predictive precision,and greatly improved the efficiency of field measurement. The results of this study could be suitably applied to measure SP（n max）in practice.