Relationships among water dynamics, soil moisture and vapor pressure deficit in a Larix gmelinii stand, eastern boreal Siberia

To clarify the relationships among water dynamics, soil water content and vapor pressure deficit (VPD) in a Larix gmelinii stand, eastern boreal Siberia, seasonal fluctuation of the stand water use (SF) and environmental factors were measured. SF increased rapidly after the needle flushing and reached the maximum value (2.7 mm d^-1) around the middle of June, when needle expansion ceased. Thereafter, it decreased sharply and was maintained at about 75% level of the peak value till the end of July. The tendency for SF to level off at high VPD could be observed. From the analysis of the effect of soil water content (SWC) on canopy stomatal conductance, a close linear relation could be found between stomatal conductance and SWC at VPD<20 hPa. However, this relation was not so clear at VPD≥20 hPa due to the effect of VPD on SF. In order to survive under the semi-arid environment, L. gmelinii could minimize the water loss with transpiration and avoid the water stress by regulating its stomatal conductance in response to soil water conditions.