Si, Bingcheng2019-09-192019-09-192019-082019-09-19August 201http://hdl.handle.net/10388/12336This research was conducted in a native jack pine stand within Narrow Hills Provincial Park, Saskatchewan, Canada. The goals of this research were to 1) compare jack pine sap flow with environmental parameters (volumetric water content of the soil [VWC], net radiation, air humidity, air temperature, and wind speed) and internal water storage in the tree under pre-augmented (normal) conditions and augmented (drought) conditions, and 2) demonstrate that at a sandy site under drought conditions jack pine trees facilitate hydraulic redistribution of soil water. Net radiation, air humidity, and VWC were the primary drivers of sap flow within jack pine trees in this study. Net radiation was the primary driver of sap flow throughout the day. Air humidity was important for inducing sap flow. The VWC was influential on the volume of water being transported up the tree to support transpiration. Sap flow was found to have hysteretic relationships with all environmental parameters except VWC. Throughout the diurnal cycle, sap flow and the tree trunk circumference have a divergent and hysteretic relationship. The daily amplitude of the change in tree trunk circumference was primarily controlled by sap flow, however the overall circumference of the tree trunk was controlled by the VWC and internal water storage. Jack pine trees only exhibited tree growth under normal conditions on days where sap did not flow. Jack pine tree trunk circumference contracted under drought conditions as the tree used internal water storage to supply evapotranspiration. The movement of an isotopically labelled solution was used to demonstrate that at a sandy site under drought conditions, jack pine trees facilitate hydraulic redistribution. After injecting the isotopically labelled solution to a depth of 100 cm below the soil surface, soil water collected from 0 cm – 20 cm and 80 cm – 120 cm had statistically significantly higher δ2H values compared to baseline δ2H values. At the same time, the δ2H values of soil water collected from 20 cm – 80 cm were statistically not different compared to baseline δ2H values. The presence of the isotopically labelled solution at 0 cm – 20 cm and 80 cm – 120 cm, and absence of it between 20 cm – 80 cm, indicated jack pine trees facilitated hydraulic redistribution using their taproot and lateral roots.application/pdfJack pine treeshydraulic redistributionwater storagehysteresisdendrometers, heat pulse probesdroughtThesis2019-09-19