中文摘要：

许多研究近似在生长和树的 ecophysiological 特点估计了低土壤温度的阀值的范围，但是困难地决定了准确价值。为了解决这个问题，黑云杉(Picea mariana ) 和杰克松(Pinus banksiana ) ，幼苗在温室暴露于 5， 10， 15， 20， 25， 30 和 35 ° C 土壤温度。在 90 天处理以后，捕捞光合的率(A) ，有气孔的传导力(g _s ), 蒸发率(E) ，水使用效率(WUE ) 和特定的叶区域(SLA ) 被测量。这研究证明所有特点与改变土壤温度有一种不均匀的山峰关系，关系很好用一个立方的曲线的模型被模仿，并且准确阀值能从模型的第二衍生物被导出。结果表明阀值在 ecophysiological 特点之中并且在树种类之间变化了。在黑云杉，阀值是为 A 的 14.1， 14.7， 10.7， 14.4 和 16.2 ° C， g _s , E， WUE 和 SLA；为在杰克松的相应特点的 15.4， 10.4， 14.7， 16.9 和 10.5 ° C。在黑云杉和 g _{在杰克松的 s} 是为生态生理学的常规过程代表土壤温度的最小的要求的指示物。在黑云杉的 SLA 和在杰克松的 WUE 的最高的阀值建议他们对减少的土壤温度最敏感并且可以在环境适应起一个重要作用。平均阀值在为黑云杉和杰克松的 14.0 和 13.6 ° C，建议到低土壤温度的种类的敏感是相当靠近的。

英文摘要：

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.