Phenotypic Variation in Climate-Associated Traits of Red Spruce (Picea rubens Sarg.) along Elevation Gradients in the Southern Appalachian Mountains

Red spruce (Picea rubens) is a long-lived tree species that thrives in cool, moist environs. Its ability to adapt to rapidly changing climate is uncertain. In the southern Appalachian Mountains, red spruce reaches its greatest abundance at high elevations, but can also occur across a range of mid and lower elevations, suggesting the possibility of a correlation between genetic variation and habitat. To assess clinal phenotypic variation in functional traits related to climate adaptation, we collected seed from 82 maternal sib families located along replicated elevational gradients in the Great Smoky Mountains National Park, TN (GSMNP) and Mount Mitchell State Park, NC (MMSP). The percentage of filled seeds and seed mass increased with elevation, indicating that successful pollination and seed development was greatest at the highest elevations. Seedlings sourced from GSMNP displayed a strong relationship between elevation and bud set when grown under common garden conditions. High elevation families set bud as many as 10 days earlier than low elevation families, indicating adaptation to local climate. Across parks, no effect of elevation was noted for bud flush. Our results demonstrate that red spruce in the southern Appalachian Mountains displays clinal variation in bud set that may reflect local adaptation to climate, although this varied between the two parks sampled. We suggest that genetic adaption of red spruce to different climate regimes, at both local and broad spatial scales, is in need of more intensive study, and should be carefully considered when selecting seed sources for restoration.

红云杉（Picea Rubens）是一种长寿命的树种，在凉爽潮湿的环境中壮成长。它适应快速变化的气候的能力尚不确定。在阿巴拉契亚南部的山脉中，红云杉在高海拔时达到了最大的丰度，但也可以发生在一系列中和较低海拔的范围内，这表明遗传变异与栖息地之间存在相关性。为了评估与气候适应相关的功能性状中的clinal表型变化，我们从沿田纳西州大烟山国家公园（GSMNP）和NC（MMSP）的大烟山国家公园（GSMNP）和米切尔山州立公园（GSMNP）和NC（MMSP）中的82个母体SIB家族收集了种子。填充的种子和种子质量的百分比随海拔高度增加，表明在高海拔地区，成功的授粉和种子发育最大。源自GSMNP的幼苗在常见的花园条件下生长时，海拔和芽套之间表现出牢固的关系。高海拔家族的芽比低海拔家族早10天，表明适应当地气候。在整个公园中，没有发现海拔的影响。我们的结果表明，阿巴拉契亚南部山脉的红云杉显示出芽组中的狭窄变化，这可能反映了局部对气候的适应，尽管这两个公园在两个公园之间有所不同。我们建议，在局部和广泛的空间尺度上，红云杉对不同气候状态的遗传适应需要更深入的研究，在选择恢复种子来源时，应仔细考虑。