LAUSR

Trees may migrate northward in response to climate change and become exposed to new photoperiod and soil moisture regimes. This study assessed the impacts of photoperiod and its interaction with soil moisture and carbon dioxide concentration ([CO2]) on the hydraulic conductivity in jack pine and its vulnerability to xylem embolism. Seedlings were exposed to 400 vs. 950 µmol mol-1 [CO2], 60–70% vs. 30–40% (of field capacity) soil moisture and photoperiods of seed origin, and 5o and 10o north of seed origin in greenhouses. Cavitation vulnerability curves were measured for determining the xylem pressure at which 50% hydraulic conductivity was lost (ΨPLC50). It was found that elevated [CO2] significantly increased hydraulic conductivity while low soil moisture decreased it. Under elevated [CO2], the xylem became progressively more vulnerable to embolism with changes in photoperiod regime from the seed origin to 10o north of the seed origin, as indicated by the progressively less negative ΨPLC50. However, no s...