Research On Transpiration Of Larix Gmelinii In Northern Da Xing’an Mountains

In this study, by Granier thermal dissipation probe (TDP) method, Larix gmelinii transpiration were continuously observed in northern Da Xing’an Mountains from May to September in2012. Integrated with simultaneous environmental factors, transpiration of Larix gmelinii and its relationship with influencing factors were investigated. The results showed that1) Larix gmelinii transpiration rate showed significant diunal variations which presented unimodal curves in sunny and cloudy days, and bimodal or multimodal curves in rainy days, respectively. Transpiration rates of sunny and cloudy days were higher than those of rainy days. The list of ratio of night sap flow flux accounting for a full day’s flow flux was the sunny day(5.91%)> rainy day (4.88%)> cloudy day(2.57%). In the case of high temperature and no rain, the sap flow presented a decreasing trend with the rainless and hot days increasing.2) daily peak of Larix gmelinii sap flow rate was high in June to August, and it reached the highest value of23.62cm3/(cm2·h), the transpiration in June to August accounted for80%of the total water consumption during observation period. The daily peak in May was less and it got the lowest value of2.03cm3/(cm2·h) in September.3) Good correlation existed between the sap flow rate and environmental factors, just as the coefficient of determination of their multiple regression model was0.79. Further correlation analyses indicated that the main environmental factors influencing sap flow density in the growing season were vapor pressure deficit and photosynthetic active radiation.4) The total transpiration of the Larix gmelinii stand during the growing season was566.49t/hm2,that is56.65mm, accouting for12%of rainfall in the same period.