Data_Sheet_1_Non-linear Response to Cell Number Revealed and Eliminated From Long-Term Tracheid Measurements of Scots Pine in Southern Siberia.PDF

Dendroclimatic research offers insight into tree growth–climate response as a solution to the forward problem and provides reconstructions of climatic variables as products of the reverse problem. Methodological developments in dendroclimatology have led to the inclusion of a variety of tree growth parameters in this field. Tree-ring traits developed during short time intervals of a growing season can potentially provide a finer temporal scale of both dendroclimatic applications and offer a better understanding of the mechanisms of tree growth reaction to climatic variations. Furthermore, the transition from classical dendroclimatic studies based on a single integral variable (tree-ring width) to the modern multitude of quantitative variables (e.g., wood anatomical structure) adds a lot of complexity, which mainly arises from intrinsic feedbacks between wood traits and muddles seasonality of registered climatic signal. This study utilized life-long wood anatomical measurements of 150- to 280-year-old trees of Pinus sylvestris L. growing in a moisture-sensitive habitat of the forest-steppe of Southern Siberia (Russia) to investigate and eliminate legacy effect from cell production in tracheid traits. Anatomical parameters were calculated to describe the results of the three main subsequent stages of conifer xylem tracheid development, namely, cell number per radial file in the ring, mean and maximum cell radial diameter, and mean and maximum cell-wall thickness. Although tree-ring width was almost directly proportional to cell number, non-linear relationships with cell number were revealed in tracheid measurements. They exhibited a stronger relationship in the areas of narrow rings and stable anatomical structure in wider rings. The exponential models proposed in this study demonstrated these relationships in numerical terms with morphometric meaning. The ratio of anatomical measurements to their modeled values was used to develop long-term anatomical chronologies, which proved to retain information about climatic fluctuations independent of tree-ring width (cell number), despite decreased common signal.

树木气候学研究（dendroclimatic research）既可通过正问题求解以揭示树木生长-气候响应关系，又可通过逆问题推演以重建气候变量序列。树木气候学（dendroclimatology）的方法学进展使得该领域纳入了多样的树木生长参数。在生长季短时段内形成的年轮性状（tree-ring traits），有望为树木气候学应用提供更精细的时间尺度，同时增进对树木生长响应气候变异的机制理解。此外，从基于单一整合变量（single integral variable）的经典树木气候学研究，转向涵盖多类定量变量（quantitative variables，如木材解剖结构（wood anatomical structure））的现代研究范式，大幅增加了研究复杂度——这一复杂度主要源于木材性状（wood traits）间的内在反馈机制，且会模糊所记录气候信号的季节性。本研究针对生长于俄罗斯西伯利亚南部森林草原水分敏感生境中的150至280年生欧洲赤松（Pinus sylvestris L.），利用其终生木材解剖测量数据，探究并消除管胞性状（tracheid traits）中的细胞生产遗留效应（legacy effect）。研究计算了三类表征针叶树木质部管胞（xylem tracheid）发育三个主要连续阶段的解剖参数：年轮内径向列细胞数、平均及最大细胞径向直径，以及平均及最大细胞壁厚度（cell-wall thickness）。尽管年轮宽度（tree-ring width）几乎与细胞数呈直接正比关系，但管胞测量结果显示其与细胞数存在非线性关系（non-linear relationships）：在窄年轮区域二者相关性更强，而宽年轮区域则呈现稳定的解剖结构特征。本研究提出的指数模型（exponential models）以量化形式呈现了这些关系并赋予其形态学意义，通过将解剖测量值与模型预测值的比值构建了长期解剖学年表（anatomical chronologies）。尽管该类年表的共同信号（common signal）强度有所降低，但仍保留了独立于年轮宽度（及细胞数）的气候波动（climatic fluctuations）信息。