Features and Influence Fectors of the Sugar Maple Sap Flow in the Non-growing Seasons

In order to understand the dynamics variation characteristics of Acer saccharum sap flow of during 4 years, the sap flow rate was measured from September 2016 to March 2017 by the Sap Flow Set EMS 62, and environmental factors were recorded by the automatic meteorological station. The results showed that (1) diurnal changes of A. saccharum sap flow were of multiple peak types in different months, the high peak happened in daytime and low peak in nighttime. There were obvious characteristics of night sap flow and the durations of zero-rate sap flows varied. (2) The sap flow rate decreased generally from September 2016 to March 2017. (3) In September, the diurnal changes of the sap flow of A. saccharum displayed a single peak type. The order of the sap flow rate in different weather conditions were as follows:sunny > cloudy > rainy day. (4) The sap flow rate of main trunks were higher than that of branches in all weather conditions. But the peak value varied. (5) During the non-growing season, there was a significantly positive correlation between sap flow and light radiation or air temperature, and a significantly negatively correlated with the air humidity or soil moisture.