Abstract：
Climate change (CC) necessitates reforestation/afforestation programs to mitigate its impacts and maximize carbon sequestration. But comprehending how tree growth, a proxy for fitness and resilience, responds to CC is critical to maximize these programs\' effectiveness. Variability in tree response to CC across populations can notably be influenced by the standing genetic variation encompassing both neutral and adaptive genetic diversity. Here, a framework is proposed to assess tree growth potential at the population scale while accounting for standing genetic variation. We applied this framework to black spruce (BS, Picea mariana [Mill] B.S.P.), with the objectives to (1) determine the key climate variables having impacted BS growth response from 1974 to 2019, (2) examine the relative roles of local adaptation and the phylogeographic structure in this response, and (3) project BS growth under two Shared Socioeconomic Pathways while taking standing genetic variation into account. We modeled growth using a machine learning algorithm trained with dendroecological and genetic data obtained from over 2600 trees (62 populations divided in three genetic clusters) in four 48-year-old common gardens, and simulated growth until year 2100 at the common garden locations. Our study revealed that high summer and autumn temperatures negatively impacted BS growth. As a consequence of warming, this species is projected to experience a decline in growth by the end of the century, suggesting maladaptation to anticipated CC and a potential threat to its carbon sequestration capacity. This being said, we observed a clear difference in response to CC within and among genetic clusters, with the western cluster being more impacted than the central and eastern clusters. Our results show that intraspecific genetic variation, notably associated with the phylogeographic structure, must be considered when estimating the response of widespread species to CC.
摘要：
气候变化（CC）需要重新造林/造林计划，以减轻其影响并最大程度地吸收碳。但是理解树木是如何生长的，健身和复原力的代表，对CC的响应对于最大限度地提高这些计划的有效性至关重要。跨种群的树木对CC的反应的变异性可能会受到包括中性和适应性遗传多样性的站立遗传变异的影响。这里,提出了一个框架，以评估种群规模的树木生长潜力，同时考虑到长期遗传变异。我们将这个框架应用于黑云杉(BS，PiceaMariana[Mill]B.S.P.），目标是（1）确定1974年至2019年影响BS生长响应的关键气候变量，（2）检查本地适应和该响应中的系统地理结构的相对作用，（3）在考虑遗传变异的同时，在两个共享的社会经济途径下预测BS的增长。我们使用机器学习算法对生长进行建模，该算法使用了从四个48岁的普通花园中的2600多棵树（62个种群分为三个遗传簇）获得的树状生态学和遗传数据进行了训练。并在共同的花园位置模拟生长直到2100年。我们的研究表明，夏季和秋季的高温对BS的生长产生了负面影响。由于变暖，预计到本世纪末，该物种的生长将下降，表明对预期CC的适应不良，并对其固碳能力构成潜在威胁。话虽如此，我们观察到遗传簇内和遗传簇之间对CC的反应有明显差异，西部集群比中部和东部集群受到的影响更大。我们的结果表明，种内遗传变异，特别是与系统地理结构相关的，在估计广泛物种对CC的反应时必须考虑。
