Abstract：
Tree seedlings from populations native to drier regions are often assumed to be more drought tolerant than those from wetter provenances. However, intraspecific variation in drought tolerance has not been well-characterized despite being critical for developing climate change mitigation and adaptation strategies, and for predicting the effects of drought on forests. We used a large-scale common garden drought-to-death experiment to assess range-wide variation in drought tolerance, measured by decline of photosynthetic efficiency, growth, and plastic responses to extreme summer drought in seedlings of 73 natural populations of the two main varieties of Douglas-fir (Pseudotsuga menziesii var. menziesii and var. glauca). Local adaptation to drought was weak in var. glauca and nearly absent in menziesii. Var. glauca showed higher tolerance to drought but slower growth than var. menziesii. Clinal variation in drought tolerance and growth species-wide was mainly associated with temperature rather than precipitation. A higher degree of plasticity for growth was observed in var. menziesii in response to extreme drought. Genetic variation for drought tolerance in seedlings within varieties is maintained primarily within populations. Selective breeding within populations may facilitate adaptation to drought more than assisted gene flow.
摘要：
通常认为，从原生种群到较干燥地区的树苗比来自潮湿来源的树苗更具耐旱性。然而,尽管对制定缓解和适应气候变化的战略至关重要，但耐旱性的种内变异尚未得到很好的表征，预测干旱对森林的影响。我们使用了大规模的普通花园干旱至死亡实验来评估耐旱性的大范围变化，通过光合效率的下降来衡量，增长,道格拉斯冷杉两个主要品种（Pseudotsugamenziesiivar）的73个自然种群的幼苗对夏季极端干旱的塑性响应。menziesii和var.glauca）。var地区对干旱的适应较弱。glauca和几乎不在门齐西伊。VAR。与var相比，glauca表现出更高的耐旱性，但生长较慢。Menziesii.耐旱性和整个物种生长的临床变化主要与温度而不是降水有关。在var中观察到更高的生长可塑性。menziesii应对极端干旱。品种内幼苗耐旱性的遗传变异主要在种群内维持。种群内的选择性育种可能比辅助基因流更有利于适应干旱。
