Abstract:

In this article, GREENSPAN sap flow system was used to monitor the dynamics of trunk sap flow of Ginkgo biloba. The results indicated that sap flow velocity was significantly different at different heights, depths and directions of the trunk. Sap flow velocity of upper position at the trunk was more than that of the middle and lower position. But cumulative flux was not significantly different at upper, middle and lower section. Sap flow velocity at 10 mm was the most and that at 20 mm was the least, but sap flow velocity at 5 mm and 15 mm was similar and took the second place among four depths. It also showed that sap flow velocity of the south was the most and that of the west was the second place among the different directions. And an Automatic Weather Station of HOBO was synchronously applied to measure meteorological parameters, which were used to analyze the relationship with changes of trunk sap flow velocity. The results indicated that change of sap flow velocity was a single-peak curve in fine day and multi-peak curve in cloudy and rainy day. In addition, Stepwise regression analyses revealed that PAR, temperature and wind speed were the main environmental factors affecting sap flow velocity. The efficient means to reduce water transpiration of the trees were tried to find through investigating the effect of techniques for inhibiting transpiration including pruning-leaf, overshadowing, spraying of antitranspirants. And the results indicated that spraying of antitranspirants, pruning-leaf and overshadowing could significantly reduce transpiration but the effect of pruning-leaf and overshadowing was far better than that of spraying of antitranspirants.

Key words: Ginkgo biloba, trunk sap flow, heat-pulse technique, transpiration