Due to its ubiquity across northern latitudes, silver birch (Betula pendula Roth) is an attractive model species for studying geographical trait variation and acclimation capacity. Six birch provenances from 60 to 67°N across Finland were grown in a common garden and studied for provenance and genotype variation. We looked for differences in height growth, photosynthetic gas exchange and chlorophyll content index (CCI) and compared the gas exchange of early and late leaves on short and long shoots, respectively. The provenances stratified into southern and northern groups. Northern provenances attained less height growth increment and had higher stomatal conductance (g_s) and lower intrinsic water-use efficiency (WUE, A_net/g_s) than southern provenances, whereas net photosynthesis (A_net) or CCI did not show clear grouping. Short shoot leaves had lower g_s and higher WUE than long shoot leaves in all provenances, but there was no difference in A_net between shoot types. The separation of the provenances into two groups according to their physiological responses might reflect the evolutionary history of B. pendula. Latitudinal differences in gas exchange and water use traits can have plausible consequences for global carbon and water fluxes in a warming climate.

中文翻译：

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北欧银桦（Betula pendula Roth）的南部和北部种源在生长和气体交换方面的差异

由于其在北纬地区的普遍性，白桦（Betula pendula Roth）是研究地理性状变异和适应能力的有吸引力的模式物种。在一个共同的花园中，有六种桦木种源在60至67°N的芬兰范围内种植，并研究了种源和基因型变异。我们寻找高度生长，光合气体交换和叶绿素含量指数（CCI）的差异，并分别比较了短枝和长枝上早叶和晚叶的气体交换。物源分为南部和北部组。北部种源的高度增长增量较小，气孔导度（g _s）较高，内在水分利用效率较低（WUE，A _net /g _s）高于南方种源，而净光合作用（A _net）或CCI没有显示清晰的分组。在所有种源中，短枝叶的g _s值和长枝叶的WUE值均高于长枝叶，但枝条类型之间的A_网没有差异。根据种源的生理反应将种源分为两组，可能反映了B. pendula的进化史。气体交换和用水特征的纬度差异可能会对气候变暖中的全球碳和水通量产生合理的影响。