Tree Physiology Advance Access originally published online on September 28, 2009
Tree Physiology 2009 29(11):1341-1348; doi:10.1093/treephys/tpp079
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Low moisture availability inhibits the enhancing effect of increased soil temperature on net photosynthesis of white birch (Betula papyrifera) seedlings grown under ambient and elevated carbon dioxide concentrations
1 Faculty of Forestry and the Forest Environment, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada
2 Corresponding author (qdang{at}lakeheadu.ca)
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Abstract |
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White birch (Betula papyrifera Marsh.) seedlings were grown under two carbon dioxide concentrations (ambient: 360 µmol mol–1 and elevated: 720 µmol mol–1), three soil temperatures (5, 15 and 25 °C initially, increased to 7, 17 and 27 °C, respectively, 1 month later) and three moisture regimes (low: 30–40%; intermediate: 45–55% and high: 60–70% field water capacity) in greenhouses. In situ gas exchange and chlorophyll fluorescence were measured after 2 months of treatments. Net photosynthetic rate (An) of seedlings grown under the intermediate and high moisture regimes increased from low to intermediate Tsoil and then decreased to high Tsoil. There were no significant differences between the low and high Tsoil, with the exception that An was significantly higher under high than low Tsoil at the high moisture regime. No significant Tsoil effect on An was observed at the low moisture regime. The intermediate Tsoil increased stomatal conductance (gs) only at intermediate and high but not at low moisture regime, whereas there were no significant differences between the low and high Tsoil treatments. Furthermore, the difference in gs between the intermediate and high Tsoil at high moisture regime was not statistically significant. The low moisture regime significantly reduced the internal to ambient CO2 concentration ratio at all Tsoil. There were no significant individual or interactive effects of treatment on maximum carboxylation rate of Rubisco, light-saturated electron transport rate, triose phosphate utilization or potential photochemical efficiency of photosystem II. The results of this study suggest that soil moisture condition should be taken into account when predicting the responses of white birch to soil warming.
Keywords: boreal trees, chlorophyll fluorescence, CO2 enrichment, global change, stomatal and non-stomatal limitations
Received June 15, 2009; Accepted August 21, 2009