| To examine spatial-temporal dynamic patterns of tree water relations and their controlling factors, we transplanted 8-year-old Dahurian larch (Larix gmelinii Rupr.) trees to the southern boundary of its distribution area from four locations, i. e., Tahe (52°31′N, 124°39′E), Songling (50°43′N, 124°25′E), Sunwu (49°13°N, 127°12′E) and Dailing (47°05′N, 128°54′E), comprising four experimental treatments. The heat balance method was applied to measure stem sap flow for the larch trees, while an automatic weather station with Campbell Scientific dataloggers was used to measure associated environmental factors. The sap flow density basically showed a bell-shaped diurnal pattern, but the daily maximum value of sap flow density occurred at different times depending on growing seasons and experimental treatments. The mean sap flow flux per unit sapwood area of the four treatments varied 26.24～54.45 g·cm-2·d-1, 114.33～355.39 g·cm-2·d-1 and 58.32～304.03 g·cm-2·d-1 during prior to foliar expanding, foliar expanding, and posterior to foliar expanding periods, respectively. The amount of daily water assumption was significantly positively correlated to stem diameter at 10 cm above ground surface; while sap flow flux per unit sapwood area was significantly correlated to the length of needles during the foliar expanding period. The environmental factors influencing sap flow density, including solar radiation, vapor pressure deficit, relative humidity, air temperature and wind speed, changed with the growing periods and treatments, among which the solar radiation was usually the key factor. Water potential of leaf in four experimental treatments in May more than in June to September, it arrived peak at 3:00～5:00 and got low at 12:00～14:00. while sap flow flux per unit sapwood area was significantly correlated to the Water conductivity during the foliar expanding period. Water comsumption in the growing season order: Sunwu (280.44 kg)＞Dailing (245.13 kg)＞Songling (90.17 kg)＞Tahe (24.29 kg).
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