Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black sp...Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.展开更多
基金supported by the Lakehead University Graduate Fellowship, Nature Science and Engineer Research Council Scholarship of Canada (NSERC) PGS A,the National Natural Science Foundation of China (Grant No. 30872000)K. C. Wong Education Foundation of Hong Kong (2008) and the funding initiative of Institute of Mountain Hazards and Environment, Chinese Academy of Sciences to the author and NSERC research grant to Qing-Lai Dang
文摘Many studies have estimated approximately ranges of thresholds of low soil temperature in the growth and ecophysi-ological traits of trees, but difficultly determined the exact values. To resolve the problem, black spruce （Picea mariana） and jack pine （Pinus banksiana） seedlings were exposed to 5, 10, 15, 20, 25, 30 and 35℃ soil temperature in greenhouses. After 90 days of the treatment, net photosynthetic rate （A）, stomatal conductance （gs）, transpiration rate （E）, water use efficiency （WUE） and specific leaf area （SLA） were measured. This study showed that all the traits had an asymmetrical peak relationship with changing soil temperature, the relationship was well simulated using a cubic curvilinear model, and the exact thresholds could be derived from the second derivative of the model. The results revealed that the thresholds varied among ecophysiological traits and between tree species. In black spruce, the thresholds were 14.1, 14.7, 10.7, 14.4 and 16.2℃ forA, gs, E, WUE and SLA; 15.4, 10.4, 14.7, 16.9 and 10.5℃ for the corresponding traits in jack pine. The lowest thresholds of E in black spruce and gs in jack pine were an indicator representing the minimum requirement of soil temperature for the regular processes of ecophysiology. The highest thresholds of SLA in black spruce and WUE in jack pine suggest they are the most sensitive to decreasing soil temperature and may play an important role in the acclimation. The averaged thresholds were at 14.0 and 13.6℃ for black spruce and jack pine, suggesting that the sensitivity of both species to low soil temperature was quite close.
