Tree-ring anatomy to study two thousand years of climate variability and black spruce adaptations

树木年轮常被用来重建过去的气候和分析森林生态系统对干扰和气候变化的响应。然而，使用传统的研究方法，我们不能利用树木年轮中包含的所有信息，我们有可能获得有偏见的解释。另一方面，同时使用几个树木年轮特征和年度内分辨率分析，即每个年轮不止一次测量，可以为我们提供更精确和详尽的气候变率和树木生态生理信息。在这个研究项目中，我们将测量过去两千年来树轮年表的战略网络样本的多个树轮解剖特征，这些样本是由来自魁北克北方森林的亚化石和活黑云杉产生的。解剖特征将以年内分辨率进行分析，包括气管管腔面积、气管壁厚度和解剖密度等。这些特征具有特定的气候敏感性，并与生长季节影响树木生长的水和热约束直接相关。此外，我们将利用我们的解剖数据来改进气候变化背景下北方乔木木材生物量积累的生态生理模型。这个研究项目具有创新潜力，因为我们将开发高通量的解剖测量系统，目前只有极少数实验室在世界上管理。然后，我们将利用最有希望的解剖学特征，并将它们与我们已经测量过的树木年轮特征（宽度、密度、纤维素的稳定同位素）结合起来，显著改善魁北克北方地区的气候重建。我们的年内解剖特征也将首次允许重建过去的季节湿度和温度变化，并评估它们对北方森林树木功能的影响。最后，我们将使用基于已开发的生态生理模型反演的新技术来验证考虑树功能规则是否会修改传统方法获得的树气候重建结果。我们所有的数据都将提供给其他用户，并将为气候重建提供新的参考，因为目前，尽管树突解剖学的潜力得到了认可，但尚未开发出涵盖过去两千年的解剖特征年表。

Tree-rings are often used to reconstruct past climate and analyze forest ecosystem responses to disturbances and climate change. However, with traditional research methods we do not exploit all the information contained in tree-rings and we risk to obtain biased interpretations. The use of several tree-ring traits simultaneously and of intra-annual resolution analyses, i.e. more than one measurement per each annual growth ring, may on the other hand give us more precise and exhaustive information on climate variability and tree ecophysiology. For this research program, we will measure multiple tree-ring anatomical traits on the samples of a strategic network of tree-ring chronologies spanning the last two millennia and produced with subfossil and living black spruce trees from the Quebec boreal forest. The anatomical traits will be analyzed with intra-annual resolution and will include, for example, the tracheid lumen area, the tracheid wall thickness and the anatomical density. These traits have a specific climatic sensitivity and are directly related to water and thermal constraints that influence tree growth during the growing season. In addition, we will use our anatomical data to improve the ecophysiological modeling of wood biomass accumulation in boreal trees in the context of climate change. This research program has innovative potential because we will develop high throughput systems for anatomical measurements which are currently managed only by very few laboratories in the world. Then, we will significantly improve the climate reconstructions for the Quebec boreal region by using the most promising anatomical traits and by combining them with the tree-ring traits that we have already measured (width, density, stable isotopes of cellulose). Our intra-annual anatomical traits will also allow, for the first time, the reconstruction of past seasonal changes in humidity and temperature and the assessment of their impact on tree functioning in the boreal forest. Finally, we will use new techniques based on the inversion of the developed ecophysiological models to verify if the consideration of tree functional rules modifies the results of dendroclimatic reconstructions obtained with traditional methods. All our data will be made available to other users and will represent a novel reference for climate reconstructions because currently, despite the recognized potential of dendroanatomy, no chronology of anatomical traits covering the last two millennia has yet been developed.