Visualizing Individual Tree Differences in Tree-Ring Studies
AbstractAveraging tree-ring measurements from multiple individuals is one of the most common procedures in dendrochronology. It serves to filter out noise from individual differences between trees, such as competition, height, and micro-site effects, which ideally results in a site chronology sensitive to regional scale factors such as climate. However, the climate sensitivity of individual trees can be modulated by factors like competition, height, and nitrogen deposition, calling attention to whether average chronologies adequately assess climatic growth-control. In this study, we demonstrate four simple but effective methods to visually assess differences between individual trees. Using individual tree climate-correlations we: (1) employed jitter plots with superimposed metadata to assess potential causes for these differences; (2) plotted the frequency distributions of climate correlations over time as heat maps; (3) mapped the spatial distribution of climate sensitivity over time to assess spatio-temporal dynamics; and (4) used t-distributed Stochastic Neighborhood Embedding (t-SNE) to assess which trees were generally more similar in terms of their tree-ring pattern and their correlation with climate variables. This suite of exploratory methods can indicate if individuals in tree-ring datasets respond differently to climate variability, and therefore, should not solely be explored with climate correlations of the mean population chronology. View Full-Text
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Trouillier, M.; Van der Maaten-Theunissen, M.; Harvey, J.E.; Würth, D.; Schnittler, M.; Wilmking, M. Visualizing Individual Tree Differences in Tree-Ring Studies. Forests 2018, 9, 216.
Trouillier M, Van der Maaten-Theunissen M, Harvey JE, Würth D, Schnittler M, Wilmking M. Visualizing Individual Tree Differences in Tree-Ring Studies. Forests. 2018; 9(4):216.Chicago/Turabian Style
Trouillier, Mario; Van der Maaten-Theunissen, Marieke; Harvey, Jill E.; Würth, David; Schnittler, Martin; Wilmking, Martin. 2018. "Visualizing Individual Tree Differences in Tree-Ring Studies." Forests 9, no. 4: 216.
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